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1
Smith, Keith H. "Pasteurization of raw skim milk by pulsed electric fields and antimicrobials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ61948.pdf.
Testo completo
2
Suozzo, Andrea M. "Pasteurization and its discontents: Raw milk, risk, and the reshaping of the dairy industry". ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/320.
Testo completoAbstract (sommario):
Milk is something many Americans consume every day, whether over cereal, in coffee or in a cup; as yogurt, cream, cheese or butter. The vast majority of that milk is pasteurized, or heated to the point where much of the bacteria in the milk dies. Pasteurization both slows spoilage of the milk and eliminates potentially harmful bacteria. The fact that we call heat-treated dairy simply "milk" is a testament to pasteurization's widespread proliferation over the past century. Prior to the 1900s, "milk" was raw and unheated, and pasteurized milk was a radically new technology. My research delved into understandings of dairy in both the present and the past, looking in the first chapter at Vermont farmer resistance at the advent of pasteurization, and in the second at consumer resistance to pasteurization in the present time.
A century ago, the dairy industry was in flux, facing pressure to change due to population shifts and rising demands. In lieu of food that could be traced to a neighbor or to a farm on the other side of town, urbanization meant that food could travel hundreds of miles before it reached its destination -- Vermont farmers could now send their fluid milk to the Boston and New York markets. Once milk got to the city, however, it was often riddled with bacteria and untraceable to its source. Cities and states struggled to regulate the safety of milk coming into their area. In 1908 the Vermont legislature passed a pasteurization law in an attempt to curb the spread of bovine tuberculosis, but farmers and creameries simply refused to follow it and the state legislature was forced to repeal the law two years later. Despite pushback to pasteurization, however, pressure from the cities forced its adoption, pushing the expense onto the middleman processors and distributors. This, in turn, helped to drive consolidation and bring about the dairy industry as we know it today -- an industry that many interviewees in my present-day research felt was deeply flawed.
My second chapter focuses on raw milk consumers in Vermont. Those on each side of the raw milk discussion make broad -- and sometimes dire -- knowledge claims regarding the values and risks associated with consumption of the substance. Advocacy groups, agricultural associations, and various governmental authorities all voice divergent opinions regarding the safety and health benefits of raw milk consumption. As such, consumers navigate these contests of voices when deciding whether or not to drink raw milk. Yet raw milk consumers are not simply passive recipients of governmental, advocacy and media messaging, but rather consumers making rational decisions based on research, experience and values. In examining how raw milk consumers understand their actions and decisions, I bring this perspective to bear on the larger discussion of the risks and benefits of raw milk consumption.
My investigation of the historical and present context of raw milk shed light not just on the subculture of those who choose to drink raw milk, or on the small group of farmers who fought back against pasteurization in 1909. It revealed common refrains over the course of more than a century, repeating patterns and, I hope, a lens through which to view the nuance and shifting possibilities in other issues in the food system, both past and current.
3
Lind, David Hilty. "Encounter on a home-delivered raw milk route". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/6003.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 2, 2008) Includes bibliographical references.
4
Garcia, Claudia [Verfasser]. "Biosensing for the analysis of raw milk / Claudia García". München : Verlag Dr. Hut, 2014. http://d-nb.info/1058285173/34.
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5
Toledo-Alonzo, Patricia. "Studies of raw milk from sustainable/organic production systems /". Uppsala : Sveriges lantbruksuniv, 2003. http://www-mat21.slu.se/publikation/pdf/Patricia.pdf.
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6
Fonteh, Florence Anyangwe. "Role of the lactoperoxidase system in raw milk preservation". Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367749.
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7
Lachowsky, William M. "Enumeration of bacteria in raw milk, evaluation of various techniques". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ33243.pdf.
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8
Ataro, A., Robert Ian McCrindle, B. M. Botha, Cheryl Myra Ethelwyn McCrindle e P. P. Ndibewu. "Quantification of trace elements in raw cow’s milk by inductively coupled plasma mass spectrometry (ICP-MS)". Elsevier, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000153.
Testo completoAbstract (sommario):
The levels of trace elements are an important component of safety and quality of milk. While certain elements
such as chromium are essential at low levels, an excess can result in deleterious effects on human
health. International quality control standards for milk are published by the Codex Alimentarious Commission
and levels of heavy metals in milk intended for human consumption are routinely monitored.
This paper describes a new method for demonstrating the levels of V, Cr, Mn, Sr, Cd and Pb in raw cow’s
milk, using an ICP-MS. Samples (n = 24) of raw cow’s milk were collected from dairy farms close to mines
in Gauteng and North West Provinces of South Africa. In order to destroy organic matrix, each freeze dried
milk sample was mineralised by using a microwave assisted digestion procedure. Concentrations of trace
elements in digested milk samples were measured by ICP-MS. A whole milk powder reference material
(NIST SRM 8435) was used to evaluate the accuracy of the proposed method. It was found that the levels
of V, Cr, Mn, Sr, Cd and Pb obtained using the new method showed concordance with certified values.
9
Giacometti, Federica <1982>. "Production and sale of raw milk: risk factors for milk contamination and risk assessment for consumers". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3914/.
Testo completo
10
Mark, Alyssa Marie. "Raw Milk Versus Conventional Milk Intake and its Effect on Nutrient Intake, Obesity and Central Adiposity". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306898153.
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11
Lukanji, Zinathi, e R. N. Ndip. "Isolation and molecular characterization of Bacillus cereus from cow’s raw milk". Thesis, University of Fort Hare, 2015. http://hdl.handle.net/10353/d1021284.
Testo completoAbstract (sommario):
Bacillus cereus is a group of ubiquitous facultative anaerobic spore forming Gram-positive rods commonly found in soil. It has been detected and implicated in several contaminated food products and raw milk in dairy farms and it causes foodborne gastroenteritis by producing several toxins. This study is aimed at characterizing virulence determinants of B. cereus from cow‟s raw milk. A total of 400 raw milk samples were collected in Fort Hare Dairy Trust and Middledrift Dairy Farm; and cultured on Polymyxin pyruvate Egg-Yolk Mannitol Bromothymol Agar (PEMBA) for 48 hours at 37°C. DNA was isolated from the isolates and 16S rDNA was amplified and sent to Central Analytical Laboratory for sequencing. The gyrB gene of B. cereus was also used to confirm the identity of the isolates. Antibiotic susceptibility profiles of the isolates together with virulence genes were investigated. Multilocus Sequence typing was used to investigate the genetic relatedness of some selected isolates. Furthermore, spores of the isolates were produced, harvested and their concentrations determined. All (100%) of the isolates were identified as having a 96-99% similarity to B. cereus, B. thuringiensis and B. anthracis using sequencing; while gyrB gene was observed in all (100%) of the isolates. Three virulence genes nheA, nheB, nheC encoding for non haemolysin enterotoxin were amplified in all (100%) the isolates. All (100%) of the isolates were susceptible to doxycycline, gentamycin, tetracycline, ciprofloxacin, chloramphenicol and streptomycin. Resistance to rifampicin and penicillin G was predominant with equal rate of 100%, while susceptibility to erythromycin, clindamycin and doxycycline ranged from 60% to 100%. The selected isolates were related and are descendants of the same ancestor. All (100%) the isolates produced spores. The B. cereus isolates contain virulence genes, has multiple antibiotic drug resistance and produce spores, which poses a health risk to the public and cannot be used as probiotics.
12
Çetin, Ali Emrah Yenidünya Ali Fazıl. "Isolation And Molecular Characterization Of Lactic Acid Bacteria From Raw Milk/". [s.l.]: [s.n.], 2002. http://library.iyte.edu.tr/tezler/master/biyoteknoloji/T000140.rar.
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13
Shao, Yanwen 1967. "High pressure treatment for enhancing safety and quality of raw milk cheese". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79123.
Testo completoAbstract (sommario):
The application of high pressure (HP) processing on raw milk cheese was investigated in order to assure safety and improve quality. Fresh raw milk cheese inoculated with contaminant, spoilage and pathogenic microorganisms (Escherichia coli K-12, E. coli O157:117 and Listeria monocytogenes), as well as natural micro-flora, were subjected to UP treatment at selected pressures (200--400 MPa) for various holding times (0 to 100 min), or number of pulses. HP destruction of microorganisms followed the dual effect destruction behavior involving a step change in the population due to a pressure pulse (pulse effect, PE) and a first order rate log-linear kinetics during the pressure hold. The pressure dependency of kinetic parameters followed the pressure destruction time (PDT) and Arrhenius type models.The results suggest that high pressure treatment as a powerful tool for microbial control do not result in major change in raw milk cheese quality properties (color and texture). It would thus be an effective method of inactivation of spoilage bacteria and pathogens for ensuring safety and keeping the quality of raw milk cheese.
14
Duarte, Carla Margarida Pinheiro Cardoso. "Portable “lab-on-chip” platform for bovine mastitis diagnosis in raw milk". Doctoral thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2016. http://hdl.handle.net/10400.5/12011.
Testo completoAbstract (sommario):
Tese de Doutoramento em Ciências Veterinárias, Especialidade de Ciências Biológicas e BiomédicasBovine mastitis is an economic burden for farmers mostly because of decreased milk yield, premature culling and cost of veterinary treatments. The identification of mastitis pathogens is of major importance in order for adequate control measures to be taken, to reduce the risk of appearance of chronic infections, and to target antimicrobial therapy. The aim of this study was to develop and validate a sensitive method for magnetic detection of Streptococcus agalactiae, Streptococcus uberis, Staphylococcus aureus and Staphylococcus epidermidis in raw milk samples. Mastitic milk samples were collected aseptically from 81 cows with subclinical mastitis, from 12 Portuguese dairy farms. Ninety one quarter milk samples were selected based on bacteriological results. All samples were submitted to PCR analysis. In parallel, these milk samples were mixed with a solution combining specific antibodies and magnetic nanoparticles, to be analyzed using a lab-on-a-chip magnetoresistive cytometer, with microfluidics sample handling. This immunological recognition was able to detect bacterial presence above 100 cfu/ ml, depending on antibody and targeted bacteria. Comparison with PCR results showed sensitivities of 73% and 41%, specificity values of 25% and 57%, and PPV values of 35% and 54% for magnetic identification of streptococci species with an anti-S. agalactiae antibody and an anti-GB Streptococcus antibody, respectively. Regarding staphylococci species, the sensitivity values found were of 57.1% and 79.3%, specificities of 75% and 50%, and PPV values of 40% and 95.8% for magnetic identification with an anti-S. aureus antibody and an anti-Staphylococcus spp. antibody, respectively. Both bacterial genus studies translated a fair expectation for a “cow-side” use application, making this integrated platform of potential use after further improvements for fast bacteriological infection screening. Some constraints are described as well as the method´s limitations in bacterial quantification.
RESUMO - Plataforma portátil “lab-on-chip” para diagnosticar mastite bovina em leite crú - A mastite bovina representa um custo económico relevante para os produtores de leite principalmente devido ao decréscimo da produção leiteira, abate prematuro e custos associados ao tratamento veterinário. Consequentemente, a identificação atempada dos agentes etiológicos é crítica para a implementação de medidas de controlo adequadas, redução do risco de infecções crónicas e aplicação de uma terapia microbiana específica. O objectivo deste estudo foi desenvolver e validar um método de detecção magnética capaz de identificar Streptococcus agalactiae, Streptococcus uberis, Staphylococcus aureus e Staphylococcus epidermidis em amostras de leite crú. As amostras de leite mastítico utilizadas foram recolhidas de 81 animais com mastite subclínica, de 12 explorações leiteiras nacionais. As amostras de leite de 91 quartos de úbere foram selecionadas tendo em conta os resultados bacteriológicos. Todas as amostras foram analisadas por PCR e pelo citómetro magnetoresistivo “lab-on-chip”, tendo sido necessário neste caso, adicionar uma solução com partículas magnéticas funcionalizadas com anticorpos específicos. Este reconhecimento imunológico detectou presença bacteriana acima das 100 ufc/ml, dependendo do anticorpo e da bactéria-alvo. Comparando com os resultados da análise por PCR, este método de detecção magnética apresentou sensibilidades de 73% e 41%, valores de especificidade de 25% e 57%, e valores VPP de 35% e 54% para identificar espécies de Streptococcus com os anticorpos anti-S. agalactiae e anti-GB Streptococcus, respectivamente. No que diz respeito às espécies de Staphylococcus, os valores de sensibilidade encontrados foram de 57.1% e 79.3%, de 75% e 50% para a especificidade, e de 40% e 95.8% para VPP com os anticorpos anti-S. aureus e anti-Staphylococcus spp., respectivamente. Os dois estudos apontam para uma potencial utilização do tipo “cow-side”, tornando a plataforma integrada potencialmente utilizável para uma rápida monitorização de infecção bacteriológica, após melhorias futuras. O método desenvolvido apresenta algumas restrições e limitações relativamente à quantificação bacteriana.
15
Louw, Celmarie. "Factors influencing the bacteriological quality of raw milk produced on dairy farms in Central South Africa". Thesis, Bloemfontein : Central University of Technology, Free State, 2013. http://hdl.handle.net/11462/204.
Testo completoAbstract (sommario):
Thesis (M. Tech. (Environmental health)) - Central University of technology, Free State, 2013Introduction Dairy farms in central South Africa produce a substantial amount of milk, which is sold in Bloemfontein, Free State. Large volumes of unpasteurized (raw) milk is collected on the dairy farms, which undergoes further processing before it reaches the consumer at the end of the production line. There is a large proportion of the population that, in most cases unknowingly, consumes raw milk that has bacterial counts substantially higher than legal standards. Poor quality unpasteurized milk is either sold as fresh milk in the informal market, or as dairy products, such as cheese, manufactured from unpasteurized milk. Consumers are therefore, in most cases, unaware of the poor quality dairy products they consume. Milk quality is usually assessed in terms of bacterial content, which include Escherichia coli, coliforms and total bacterial count. The bacterial quality of milk is influenced by a number of factors, including farming practices, structural design of the milking shed, herd health and quality of water used in the dairy. If the highest level of hygiene practices is maintained, contamination of the milk by pathogenic microorganisms will be controlled, however, any drop in the vigilance of hygiene practices could result in unacceptable high levels of pathogenic microorganisms resulting in poor quality raw milk. Poor quality raw milk will inevitably result in poor quality pasteurized milk, containing unacceptably high levels of pathogenic organisms, which will eventually reach the consumer. Objectives The objectives of this study were to assess the quality of milk and influencing factors of milk produced on 83 dairy farms that supply milk intended for further processing to the greater Mangaung region, Central South Africa. Influencing factors investigated included, water quality and hygiene of milk contact surfaces, namely pulsator surfaces and milk pipeline surfaces. Methods Standard sampling procedures were followed when milk was sampled from bulk milk tanks, water at the point of use in the dairy, as well as collection of surface swabs. Escherichia coli, coliforms, total bacterial counts and somatic cell counts in milk were determined in terms of the regulations relating to milk and dairy products, and for water in terms of drinking water standards. These data were analysed and the factors that directly influence bacterial quality of milk were identified. Results 93% of the dairy farms displayed E. coli in their bulk milk containers, which did not comply with the legal standard. For coliforms, 86% of the milk samples did not comply with the legal standard. The total bacterial count of 85% of the milk samples did comply with the legal standard. The somatic cell count of 42% of the milk samples did not comply with the legal standard. The pulsator surfaces as well as the milk pipeline surfaces of 13% of the dairy farms displayed the presence of E. coli. 80% of the pulsator surfaces and 78% of the milk pipeline surfaces did comply with the legal standard pertaining to coliforms. The total bacterial count of pulsator surfaces revealed that 19% complied, whereas 29% of the milk pipeline surfaces complied with the legal standard. The water data further revealed that 31% of the dairy farms contained E. coli in the water used in the dairies. 63% of the dairy farms contained more than the allowable number of coliforms in their water. Chi-square tests revealed significant differences (p > 0.05) between the presence or absence of E. coli in milk and water; the presence or absence of E. coli in milk and milk pipeline surfaces; the presence or absence of E. coli in milk and pulsator surfaces and the presence or absence of E. coli in milk and the positioning of the cows in the milking shed. When milk quality indexes were calculated for all the farms, only four farms were classified with excellent milk, the remainder were all classified as producing poor quality milk. The hygiene quality indexes revealed that the hygiene practices on all the farms were not up to standard. Discussion and conclusion The study revealed that the milk produced for commercial processing and distribution in the greater Mangaung region of central South Africa was of poor quality. It is often mistakenly believed that the pasteurization process will remove all microorganisms from milk. As this is not the case, it is of major concern that milk delivered commercially is not of acceptable quality. Furthermore, it could be concluded that the quality of milk products from raw milk were also probably not of acceptable quality. The results further revealed that the possible contributing factors to the poor quality milk produced by the 83 commercial dairy farms were; poor quality water used in dairy sheds and contaminated milk contact surfaces. From this study it could be concluded that the overall status of milk production on the 83 commercial dairy farms studied, did not meet the standards required for milk quality, water quality and hygiene practices.
16
Machado, Solimar Gonçalves. "Serratia and Pseudomonas as important heat-resistant protease producers in cold raw milk". Universidade Federal de Viçosa, 2015. http://www.locus.ufv.br/handle/123456789/6784.
Testo completoAbstract (sommario):
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
A estocagem de leite cru sob temperatura de refrigeração não impede o crescimento de bactérias psicrotróficas produtoras de proteases termorresistentes que comprometem a qualidade e reduzem a vida de prateleira de produtos lácteos. Para minimizar os problemas tecnológicos resultantes da atividade proteolítica, é desejável que proteases sejam detectadas e quantificadas em leite cru por um método rápido. No entanto, não existe um método eficiente para este fim. Este trabalho teve como objetivos identificar as espécies psicrotróficas com potencial de deterioração predominantes em leite cru brasileiro; identificar e caracterizar as proteases resistentes ao calor produzidas por esta microbiota e desenvolver um método rápido para detectar estas proteases em amostras de leite. As condições de armazenamento sob refrigeração foram simuladas e as bactérias psicrotróficas proteolíticas foram isoladas. As bactérias produtoras de proteases termorresistentes foram agrupadas após análise por Rep-PCR. Os testes bioquímicos e o sequenciamento dos genes rDNA 16S e rpoB foram utilizados para identificar representantes de cada grupo. Uma protease termorresistente produzida por Serratia liquefaciens foi caracterizada e o gene que codifica esta enzima foi identificado após análise dos peptídeos trípticos da protease por espectrometria de massa. Placas de microtitulação revestidas com caseína marcada com biotina foram utilizadas para quantificar a atividade proteolítica de amostras de leite e de proteases diluídas em solução tampão. Os isolados bacterianos altamente proteolíticos foram separados em oito grupos diferentes e quatro padrões únicos. Os isolados com potencial proteolítico são correspondentes à espécie Serratia liquefaciens e ao gênero Pseudomonas. Isolados de S. liquefaciens podem produzir uma metaloprotease termorresistente ao tratamento de 95 °C por 8,45 min, identificada como Ser2, com massa molar de, aproximadamente, 52 kDa e semelhante à protease AprX de Pseudomonas spp. Embora sequências de nucleotídeos do gene ser2 sejam conservadas entre os isolados de S. liquefaciens, o potencial de deterioração das estirpes é heterogêneo indicando diferenças nos níveis de expressão gênica, enzima viii ou modificações pós-transcricionais. O imunoensaio desenvolvido neste estudo foi eficiente para a quantificação da atividade de tripsina, papaína, pepsina, termolisina e protease de pâncreas bovino. No entanto, novas pesquisas devem ser realizadas para minimizar a influência dos componentes da amostra de leite nesta técnica para permitir a detecção acurada de proteases. Este trabalho destaca o elevado potencial de deterioração da microbiota encontrada em amostras de leite cru, além do desenvolvimento de um ensaio promissor, útil para a indústria de lacticínios, para detecção e quantificação de atividade proteolítica resultante das práticas agrícolas inadequadas nas propriedades produtoras de leite.
The storage of raw milk at cold temperatures does not prevent growth of psychrotrophic bacteria, which can produce heat-resistant proteases that compromise the quality and reduce the shelf life of dairy products. To minimize the technological problems resulting from proteolytic activity, these enzymes should be detected and quantified in raw milk before processing by a rapid method. However, there is no efficient method for this purpose. This work aimed to identify the predominant psychrotrophic species with spoilage potential in Brazilian raw milk, to identify and characterize the heat-resistant proteases produced by this microbiota and to developed a rapid method to detect these proteases in raw milk samples. The cold storage conditions were simulated and the psychrotrophic proteolytic bacteria isolated. The heat-resistant protease-producing bacteria were typing by Rep-PCR and clustered. Biochemical tests, 16S rDNA and rpoB gene sequencing were used for identifying one representative isolate from each cluster. The heat-resistant protease produced by Serratia liquefaciens was characterized. The encoding gene was identified after mass spectrometry analysis of tryptic peptides from the heat-resistant protease. The biotinylated casein was coated on microtiter plates and used as substrate to quantify proteolytic activity in solution and milk samples. Highly proteolytic strains were identified and characterized. The isolates were separated into eight different clusters and four solitary fingerprints. The most proteolytic isolates belonged to Serratia liquefaciens and Pseudomonas species. The S. liquefaciens isolates may produce Ser2, which is a a metalloprotease resistant to the heat treatment of 95 °C for 8.45 min. This metalloprotease showed a molecular weight of approximately, 52 kDa and a heat- resistance similar to AprX from Pseudomonas spp. Although nucleotide sequences of ser2 gene were conserved among S. liquefaciens isolates, the spoilage potential among them was heterogeneous indicating differences in enzyme expression levels or post-transcriptional modifications. The developed immunoassay was efficient for quantification of trypsin, papain, pepsin, thermolysin and protease from bovine x pancreas activity. However, further research should be performed to minimize the influence of milk components on the developed assay for detecting proteases in milk samples. This work highlighted the poor conditions of hygiene in milk farms and the high spoilage potential of the microbiota found in raw milk samples besides the development of a promising assay for detection and quantification of proteolytic activity useful for dairy industry.
17
Wirjantoro, Tri Indrarini. "A combination effect of nisin and reduced heat treatments on the keeping quality of whole milk". Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369568.
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Beattie, Sally Heather. "Incidence and importance of Bacillus species in raw milk and in the dairy environment". Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363155.
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Chand, Amita. "On-farm fractionation of milk components". The University of Waikato, 2006. http://hdl.handle.net/10289/2669.
Testo completoAbstract (sommario):
Methods for on-farm extraction of low-concentration (minor) proteins from raw whole bovine milk directly after milking were explored. These minor proteins have high commercial value. Lactoferrin (LF) and lactoperoxidase (LP) were used as model proteins for extraction using cation exchange chromatography. Laboratory fractionations showed that milk could be processed by conventional column chromatography without excessive column backpressures if resin with large particles sizes were used and the temperature was high enough so fat in the milk was malleable; ideally the milk should be near the secretion temperature of 37oC. Processing parameters such as equilibrium and dynamic capacities were determined for SP Sepharose ™ (GE Healthcare Technologies) and Bio Rex 70 (BioRad Laboratories) resins. SP Sepharose Big Beads (SP BB) were found to be more suitable than BR 70, for raw whole milk processing due to the larger size (200 um). Design considerations showed that column chromatography was not the most practical method for on-farm processing of fresh, raw whole milk. Trials with a single-stage stirred tank showed that SP BB resin could extract up to 65% of LF (initial LF concentration of 0.5 mg/mL) with a 10-minute adsorption time. The composite non-linear (CNL) model of Rowe et al. (1999) was used to describe LF uptake by SP BB resin in raw whole milk with initial LF concentrations of 0 to 1.0 mg/mL and resin:milk volume ratios of 0.010, 0.012, 0.017 and 0.024 over 45-minute contact times. The CNL model could be used to predict LF yields if initial feed concentration, milk and resin volumes, and contact times were known. Laboratory extractions showed that processing did not significantly affect bulk milk composition (fat, protein, lactose and total solids), indicating that the milk could be used for conventional processing after the minor proteins had been extracted. Resin cleaning and regeneration studies, using a procedure similar to that recommended by the resin supplier, showed that the Sepharose resin had not degraded and there was no significant decrease in binding capacity after 50 extraction cycles. A Protein Fractionation Robot (PFR) prototype based on a single-stage stirred tank and the operating parameters obtained from the laboratory trials was designed, assembled and coupled to an Automated Milking System (AMS) to process fresh, raw whole milk from individual cows immediately after milking. The LF and LP extracted from the milk from 16 individual cows were 19.7 - 55.2% (35.6 10.2%) and 21.2 - 99.5% (87.1 12.0%) respectively. Generally, higher extraction levels were obtained at higher resin:milk ratios. The amount of LF extracted on-farm agreed within 14.1 9.8% of those predicted by the CNL model, with predicted values generally being higher. The experimental on-farm adsorption values were calculated using data of LF recovered after elution, so differences between actual and predicted values may be due to losses during post-adsorption processing. Economic feasibility studies, based on experimental data from the PFR and realistic wholesale prices for LF and LP ($400 and $150/kg respectively) showed that PFR-based processing is economically viable if the farmer is paid for the LF and LP produced as well as the bulk milk. This system would have a payback period of approximately five years and an internal rate of return of 14.5%. Further case studies determined the sensitivity of the economics to various operating parameters and value/cost assumptions, including producing recombinant human protein from transgenic bovine milk. These studies showed that the higher the value of the processed raw milk, the higher the absorptive capacity of the resin, and the higher the value of the extracted protein, the more favourable the economics. In the extreme case of producing a very high value therapeutic protein (e.g. $20 000), the payback period could be as low as 0.3 years, with an internal rate of return of 818%.
20
Barros, Ana Cláudia Bizarro Brito. "Avaliação da aptidão tecnológica do leite de ovelha para o fabrico de Queijo de Azeitão DOP". Master's thesis, ISA/UTL, 2012. http://hdl.handle.net/10400.5/5311.
Testo completoAbstract (sommario):
Mestrado em Engenharia Zootécnica - Produção Animal - Instituto Superior de AgronomiaThe purpose of this study was to characterize the milk used in the manufacture of Azeitão cheese, in particular the physico-chemical properties, hygiene and technological aptitude, given the influence of milk quality in cheese making. Sampling took place from February to May and samples from raw milk sheep for the manufacture of Azeitão cheese, consisting of individual milk (one producer) or mixed (from different producers) milk, were analyzed for composition, hygiene and parameters for the assessment of the milk clotting behavior, such as clotting time, micellar aggregation properties and gel firmness. The effect of the milk producer was very significant (p <0.01) at both the physical-chemical composition, hygiene and technological aptitude, and the effect of month of production was significant only for protein content and consistency of curd. In general, the milk showed poor hygienic quality and low protein content, with negative repercussions in cheese making behaviour
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Horner, Trenton W. "Beta Galactosidose Activity of Commercial Lactase Samples in Raw and Pasteurized Milk at Refrigerated Temperatures". BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2590.
Testo completoAbstract (sommario):
Many consumers are unable to enjoy the benefits of milk, due to lactose-intolerance. Lactose-free milk is available, but at about 2 times the cost of regular milk or greater, it may be difficult for consumers to afford. The high cost of lactose-free milk is in part due to the added cost of the lactose hydrolysis process. Hydrolysis at refrigerated temperatures, possibly in the bulk tank or package, could increase the flexibility of the process, and potentially reduce the cost. A rapid β-galactosidase assay was used to determine the relative activity of commercially available lactase samples at different temperatures. Four enzymes exhibited low-temperature activity and were added to refrigerated raw and pasteurized milk at various concentrations and allowed to react for various lengths of time. The degree of lactose hydrolysis by each of the enzymes as a function of time and enzyme concentration was determined by HPLC. The two most active enzymes, as determined by the β-galactosidase assay, hydrolyzed over 98% of the lactose in 24 hours at 2°C using the supplier recommended dosage. The other two enzymes hydrolyzed over 95% of the lactose in 24 hours at two times the supplier recommended dosage at 2°C. Results were consistent in all milk types tested. The results show that it is feasible to hydrolyze lactose during refrigerated storage of milk using currently available enzymes.
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Guo, Haibin. "Combining Conventional Tests and Terminal Restriction Fragment Analysis to Evaluate Microbial Quality of Raw Milk". DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/468.
Testo completoAbstract (sommario):
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Abstract
Combining Conventional Tests and Terminal Restriction Fragment Analysis to Evaluate Microbial Quality of Raw Milk
Haibin Guo
The dairy industry is an important part in the domestic economy in the U.S. and the quality of dairy products hinges on raw milk quality. Microorganisms play a critical role in raw milk quality and they are currently tested and monitored by conventional microbiological tests. Some of the most common conventional tests include somatic cell count (SCC), standard plate count (SPC), coliform count (CC), lab pasteurized count (LPC) and proteolytic strain count (PSC). However, these methods do not correlate with each other or with the quality of milk and milk products. One factor that contributes to this lack of correlation is the insufficient knowledge of microbial communities in raw milk. In this work we aimed to evaluate modern molecular methods to complement traditional quality procedures that may eventually complement conventional tests and improve milk quality evaluation. Therefore, a molecular method, Terminal Restriction Fragment (TRF) analysis was introduced. TRF analysis has been widely used as a tool to investigate the microbial communities in environmental samples. In this study, it was applied to investigate the microbial communities in raw milk and evaluate raw milk quality.
Milk samples were collected for over six months in the Cal Poly dairy farm and evaluated by conventional tests and TRF analysis. Samples were defined as “high quality” milk and “low quality” milk according to each conventional test first. The cutoffs applied were: 50,000 cfu/ml for SPC, 70,000 cells/ml for SCC, 100 cfu/ml for CC and 250 cfu/ml for LPC. TRF analysis was conducted on raw milk samples subsequently. DNA extraction was optimized. Non-Parametric Multivariate Analysis of Variance (NPMANOVA) was applied to TRF profiles from low and high quality milk. The analysis of Similarity of Percentage (SIMPER) was used to determine each TRF peak’s contribution to the dissimilarity between the profiles of high and low quality milk. The genus/species represented by TRF peaks were estimated via database matching. In addition, conventional tests and TRF analysis were also used to analyze the factors causing low quality milk. Rain event and cow’s apparent health were the two factors investigated since raw milk samples were collected from cows in different apparent health status on wet days and dry days.
Conventional tests revealed strong correlations between the results of SPC and PSC, and SPC and CC (coefficients of correlation > 0.8). It implied that the results of conventional tests might not be independent, so the statistics based on the assumption of independence of variables were not suitable to analyze the data. SCC showed no strong correlation with any other conventional tests. Raw milk samples were grouped as high quality and low quality according to SPC, CC, SCC and LPC. Using TRF analysis, it was found that there was a significant difference between TRF profiles from low and high quality milk when the quality was defined by SPC or LPC. A TRF peak at 268 bp generated by DpnII was predominant in the TRF profiles and had high abundance in the profiles of low quality milk. Hence, Pseudomonas spp. represented by TRF peak at 268 bp was likely the predominant bacteria in the microbial community associated with raw milk. TRF peaks at 61 bp, 81 bp, 104 bp, 104 bp, 201 bp, 242 bp, 268 bp, and 270 bp contributed the most to the dissimilarity between TRF profiles from different groups of samples. In addition, the presence of DNA derived from viable but non-culturable species that were associated with raw milk quality was detected.
Rain event was the most important factor affecting the microbial quality of raw milk in this study. Both the conventional tests and TRF analysis showed that there was a significant difference between raw milk samples collected on wet days versus dry days. Samples collected on wet days harbored high bacterial counts and had high abundance of the predominant TRF peaks. In addition, the same TRF peaks contributing the most to the dissimilarity between groups separated by rain event were found to be among those contributing the most to the dissimilarity between groups of high and low quality milk defined by conventional tests. During wet days, the low quality milk was likely caused by the increased dirtiness of cow’s teats. Soil microbes are often associated with microorganisms in raw milk such as psychrotrophic bacteria, coliform groups and spore-formers. Cow’s apparent health status showed no significant influence on the microbial quality of raw milk.
Overall, the combination of conventional tests and TRF analysis can yield a comprehensive understanding of microbial community in raw milk and improve the evaluation of raw milk quality. TRF analysis was demonstrated as a useful tool and a complement to conventional tests for milk quality evaluation by providing more information on the microbial community associated with raw milk. Findings in this study can offer a basis for further study and may help the dairy industry improve raw milk quality evaluation system.
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Pandey, Pramod Kumar. "Effect of high pressure treatment of milk on cheese making process". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38508.
Testo completoAbstract (sommario):
Raw milk cheese has unique flavor and textural characteristics not obtainable in cheese from pasteurized milk. Several specialty cheeses made from raw milk are marketed worldwide, especially in Europe. However, because of safety concerns, many countries have imposed stringent restrictions on production and sale of raw milk cheeses. The purpose of this thesis research was to use high pressure (HP) treatment as a novel alternative for conventional pasteurization so that raw milk quality cheese could be produced without compromising food safety. The specific objectives of this research were to evaluate (i) the effect of HP treatment of milk on its coagulation and gelation characteristics, (ii) the destruction kinetics of microorganism and enzymes in milk, (iii) cheese making characteristics of HP treated milk as compared to the raw, pasteurized and micro-filtered milk (controls) and, finally (iv) to evaluate ripening characteristics of cheddar cheese made from HP treated milk in comparison with the controls.Three coagulation parameters of milk---lag time, mean coagulation rate, and inflexion time (time for reaching the point of maximum coagulation rate)---were evaluated as a function of pressure (200--400 MPa), temperature (3--21°C) and holding time (10--110 min) using a response surface methodology. In general, the lag time and inflexion time decreased while the mean coagulation rate increased with an increase in pressure, holding time or a decrease in temperature: The rennet gel characteristics were evaluated as gel strength (GS) and water-holding capacity (WHC). With a decrease in pressure level, temperature and holding time, there was a decrease in water-holding capacity and an increase in the gel-strength of the rennet curd. (Abstract shortened by UMI.)
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Zavelberg, Yvonne [Verfasser]. "Imperfect competition in an oligopsonistic setting : A study on the German raw milk market / Yvonne Zavelberg". Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1122285809/34.
Testo completo
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Nelson, Stephen Ernest. "Characterization Of Raw Milk Fouling On Plate-Type Heat Exchangers Using Different Alloys And Cow Phenotypes". DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/798.
Testo completoAbstract (sommario):
ABSTRACT
Characterization Of Raw Milk Fouling On Plate-Type Heat Exchangers Using Different Alloys And Cow PhenotypeS
Stephen Ernest Nelson
Milk and other dairy products are widely used in many households today. Milk is a popular beverage that is seen as a healthy alternative to other synthetic beverages such as soda pop and other sugar based drinks. It became law that milk, and milk products are pasteurized before its release to the general public (FDA 2003). Pasteurization is a thermal process where the intent is to lower the concentration of microorganisms in the milk to render it safe to drink with heat (Bansal and Chen 2006). With all the thermal processing of the raw milk, this leads to thermal efficiency degradation of the heat exchangers used to pasteurize the milk (Bansal and Chen 2006) due to direct fouling of the heating surface.
The buildup of organic and inorganic matter onto a metal surface from the constant heating of the milk on a stainless steel surface is called fouling. The exact mode on which the fouling layers nucleate and grow is unknown by the date of this writing.
Milk fouling has been around as long as the pasteurization process. (Visser and Jeurnink 1997) Fouling rate is related to a function of variables. Fouling rate is a function of milk type, time, and temperature, age of the milk, seasonal variations, process equipment design and more. The main consensus of milk fouling initiation is that of the whey protein b-Lactoglobulin which constitutes about 0.32% in whole milk (de Jong 1997; Bansal and Chen 2005a; Bansal and Chen 2006). Table III shows the general compositions of the constituents in milk.
In order to look for dependence between milk phenotypes and heated surface alloys, a design of experiment (DOE) was made. The experiment used three types of milk phenotypes to test for fouling differences. Also, four alloy compositions were also tested against the milk phenotypes. This produced a three by four matrix of variable combinations or 3x4 factorial design. It was hoped that these combinations will show a certain, but repeatable process condition which will produce lower fouling rate versus the control milk type. The milk phenotypes used in this experiment are phenotype AB-AB (control), AB-AA, and AB-BB. The phenotype of label before the hyphen was the k-casein phenotype, the label after the hyphen represented the b-Lacto globulin phenotype. The four metal types tested were stainless steel 304 (control), stainless steel 316, stainless steel 430, and titanium 6V 4Al. It was not feasible to change out the plates in the pilot scale milk pasteurizer at the pilot plant at the Dairy Products Technology Center (DPTC), or to make special replacement plates that exposed each metal to be tested on a single heat exchanger plate (AOAC-c 1995).
The manufacturing of a complete laboratory scale milk pasteurizer for the study of milk fouling on metal plates proved to be very successful. The model flow cell heat exchanger produced high enough quality of milk foulant on the test coupons in comparison to the large scale fouling layers found in full scale dairy heat processing equipment. Although generally speaking, there was not a significant technology breakthrough of using different alloys as the material for the plates in milk pasteurizer heat exchangers, a method of creating the milk fouling layer on a smaller scale can be very useful in future works studying milk fouling. The titanium alloy showed a significantly lower fouling rate, this was probably mostly due to the highly passivated surface of the Titanium. It was also seen that the actual breed of cow could have played a significant role in fouling. The new FCHE model was produced to show the viability of creating a biofilm or milk fouling layer on any material provided that it is rigid enough. Microorganisms were also briefly studied on the foulant layer that was produced with the flow cell. This new approach should provide a basis for new and more advanced research of the mechanisms and nature of milk fouling in heat processing equipment.
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Looney, Melissa Ann. "Characterization of changes in composition and physicochemical properties of casein micelles from raw milk to buttermilk". DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1162.
Testo completoAbstract (sommario):
It is well-documented that buttermilk has poor coagulation properties due to changes that occur to the casein micelles during the butter-making process. These modifications are generally attributed to the pasteurization of the cream upon which interactions between the proteins are promoted. It was hypothesized that churning is also a critical step for the changes that occur in composition of the casein micelles. The objective of this work was to learn more about the interactions that occur between casein micelles and MFGM components during the butter making process.
Raw cream was processed using a rotary churn at 18°C for approximately 30 minutes, and buttermilk was collected for analysis. Raw milk was skimmed at 10°C by centrifuging at 3000 x g for 20 minutes. Cream, skim milk and buttermilk were centrifuged at 60,000 x g for 40 minutes twice using imidazole buffer at pH 6.8 in order to isolate the micellar content in the pellet. Variation in physical properties of the casein micelles was determined using a Malvern Zetasizer. Protein profiles of UP cream, skim milk, and buttermilk were analyzed using one and two-dimensional gel electrophoresis technique. Experiments were performed using three different batches of UP cream, skim milk and buttermilk. Statistical analyses showed that processing the buttermilk significantly increased the surface charge (P0.05). Our results also indicate that churning of cream promoted interactions between casein micelles and MFGM proteins as shown by the more complex 2D-gel electrophoresis pattern obtained for casein micelles sedimented from buttermilk. This work is significant in its focus of better understanding the functionality changes of valuable milk components during the churning of cream.
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Silva, Guilherme Augusto Vieira da. "Avaliação das condições de obtenção do leite e da ação de sanificantes no tanque de expansão em uma propriedade leiteira no Município de Candeias /Bahia – estudo de caso". Programa de Pós-Graduação em Alimentos, Nutrição e Saúde (PGNUT), 2006. http://www.repositorio.ufba.br/ri/handle/ri/9550.
Testo completoAbstract (sommario):
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A demanda pela qualidade do leite vem aumentando a cada dia em todas as bacias leiteiras do país, e os produtores, para atender à indústria e aos consumidores, além do preço competitivo, precisam enfrentar o desafio de manter e garantir a qualidade do leite após a saída da fazenda. O presente estudo teve por objetivos: 1) Caracterizar as condições locais de obtenção do leite de uma fazenda no Estado da Bahia; 2) Propor e recomendar procedimentos operacionais de higiene; 3) Realizar análises microbiológicas e do pH da água utilizada na propriedade; 4) Realizar análises microbiológicas do leite cru refrigerado armazenadas no tanque de expansão; 5) Isolar e identificar as bactérias presentes no tanque de expansão; 6) Avaliar a eficiência do uso de um detergente (alcalino clorado) e três sanificantes (hipoclorito de sódio, clorexidina e ácido peracético no tanque de expansão. Como resultados, para cada um dos itens obteve-se: 1) A caracterização da fazenda revelou condições que variaram de insatisfatórias a satisfatórias para produção de leite cru resfriado, contudo, diversas deficiências quanto ao contexto higiênico-sanitário foram identificadas; 2) Na medida em que a higiene constitui fator primordial na determinação da qualidade inicial do leite, os resultados evidenciam necessidades, tanto para o estabelecimento de critérios na adoção de programas de higienização quanto de investimentos em atividades de apoio e orientação aos produtores, com o propósito de corrigir os problemas encontrados e alcançar maior eficiência nos métodos de obtenção do leite nas propriedades; 3) Foram isoladas bactérias aeróbias mesófilas, coliformes totais e fecais da agua proveniente da fonte e da torneira da propriedade, apresentando um pH de 4,0 e 4,2 na água da fonte e torneira respectivamente; 4) Foram isoladas bactérias aeróbias mesófilas, coliformes totais e fecais do leite cru refrigerado; 5) Foram isoladas do tanque de expansão as bactérias: Enterobacter spp.; Enterobacter hafnia; Pseudomonas spp.; Streptococcus spp.; Micrococcus spp Staphylococcus spp e Bacillus spp.; 6) Apesar dos resultados estatísticos não apresentarem diferenças significativas quanto a eficiência do produtos, observou-se uma média de 4,09 reduções decimais para o produto à base de hipoclorito de sódio, enquanto que o detergente clorado apresentou a menor média com 2,18 reduções decimais. Considera-se que o simples uso de tanques de expansão na atividade leiteira não significa necessariamente leite de melhor qualidade, devendo os produtores ficar atentos quanto aos aspectos de higiene em todos os processos da fazenda, investir no melhoramento da qualidade da água e educar os colaboradores no tocante a higiene pessoal e do ambiente
Salvador
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Garcia, Claudia [Verfasser], Walter [Akademischer Betreuer] Lang e Carsten [Akademischer Betreuer] Harms. "Biosensing for the analysis of raw milk / Claudia García. Gutachter: Walter Lang ; Carsten Harms. Betreuer: Walter Lang". Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072225964/34.
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Goodridge, Lawrence David. "A fluorescent bacteriophage assay for detection of Escherichia coli O157:H7 in ground beef and raw milk". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24470.pdf.
Testo completo
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Manap, Mohd Yazid B. Hj Abd. "The effects of low temperature storage and thermisation on the quality of raw and heat treated milk". Thesis, University of Glasgow, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385626.
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Caine, Lesley-Anne. "Prevalence and antibiotic resistance determinants of Escherichia coli pathotypes obtained from raw milk in two farms from the Eastern Cape, South Africa: public health implications". Thesis, University of Fort Hare, 2013. http://hdl.handle.net/10353/d1015525.
Testo completoAbstract (sommario):
Milk quality continues to be a topic of intense debate in the dairy industry, medical and public health communities. Production of maximum quantities of high-quality milk is an important goal of every dairy operation. High-quality milk must contain a low number of somatic cells and low bacteria count, and must be free of human pathogens and antibiotic residues. The objective of this study was to determine the prevalence of E. coli in unpasteurized milk recovered from Middledrift and Fort Hare dairy. In this study 400 milk samples were collected from two commercial farms (Middledrift and Fort Hare) in the Eastern Cape, South Africa, 200 raw milk samples from each farm. Samples were cultured on violet red bile mug-agar (VRB-MUG Agar) and incubated at 37ºC for 24 hours and preliminary identified by Gram stain and catalase test. Isolates that were Gram negative and catalase positive were screened for a marker of E. coli uidA gene using PCR assays. Middledrift dairy farm had 50 (25%) E. coli isolated from raw milk and Fort Hare farm showed 37 (18.5%) E. coli present in the milk samples. The presence of E. coli found in the milk samples points to the fact that fecal contamination was unavoidable and traditional practices are likely to contribute to the contamination of the milk and proliferation of the microorganisms.
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Oliveira, Camilo Ferreira de [UNESP]. "Avaliação da eficacia do tetra-test como ferramenta de gestão da qualidade do leite cru refrigerado". Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/94643.
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Este trabalho teve o objetivo de avaliar a eficácia de uma nova ferramenta de gestão da qualidade do leite cru refrigerado, comparativamente à utilização dos testes tradicionais de controle, nas condições da Instrução Normativa 51 (IN 51). Foram utilizadas 374 amostras individuais de leite cru refrigerado (produtor) e 125 amostras de leite cru de conjunto (bocas de tanques de caminhões transportadores, referindo-se a leites desses mesmos produtores). As amostras foram submetidas a duas análises microbiológicas, sendo as individuais submetidas à prova rápida de redução em tubos – o “Tetra-Test”, com o objetivo de estimar a carga microbiana do leite e a microbiota predominante, enquanto as amostras de conjunto foram submetidas à contagem padrão em placas (CPP) como método de referência. Paralelamente, buscou-se verificar os efeitos do processo de centrifugação nas características e/ou propriedades da matériaprima industrial durante a execução do processo por Ultra Alta Temperatura (UAT). Foram utilizadas 56 amostras de leite provenientes da linha de processamento, tomadas imediatamente antes e depois da etapa de centrifugação interposta no início do processo, as quais foram submetidas a ambos os testes microbiológicos (“Tetra- Test” e CPP), além da determinação da variabilidade da composição do leite e determinação do índice proteolítico da k-caseína. O “Tetra-test” se mostrou eficaz na avaliação da qualidade microbiológica do leite cru podendo ser utilizado como uma ferramenta de gestão, uma vez que seus resultados se correlacionaram proporcionalmente aos obtidos pela CPP e possibilitaram informações complementares sobre as características da microbiota dominante, oferecendo vantagens sobre os tradicionais testes de redução. Os resultados mostraram que grande...
This study aimed to evaluate the efficacy of a new tool for quality management of refrigerated raw milk, compared to traditional control tests in accordance to the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA) Normative Instruction No. 51. A total of 374 individual samples of refrigerated raw milk (from producers) and 125 samples of bulk raw milk (from milk transport tankers from these same producers) were studied. Samples were submitted to microbiological analyses, being individual samples submitted to rapid reduction in test tubes - the Tetra-Test, in order to estimate the microbial load of milk and predominant microbiota, while the bulk samples were analyzed by standard plate count as a reference method. At the same time, it was investigated the effects of the centrifugation on the characteristics and/or properties of industrial raw material into the incoming of UHT process. Were analyzed 56 samples of milk from the processing line, obtained immediately before and after centrifugation performed early in the process. Both of them were subjected to microbiological tests (Tetra-Test and PCA). In addition it was determined the variability of milk composition and proteolytic rate of k-casein. The “Tetra-test showed to be effective in assessing the microbiological quality of raw milk and can be used as a management tool, since its results correlated proportionally with those obtained by standard plate count and make possible to obtain more information about predominant... (Complete abstract click electronic access below)
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Queiroz, Jose Cavalcante de. "Avaliação sanitária do leite cru distribuído nos municípios de Juquitiba e Itapecerica da Serra, São Paulo - 1990-1992". Universidade de São Paulo, 1995. http://www.teses.usp.br/teses/disponiveis/6/6135/tde-01022018-145442/.
Testo completoAbstract (sommario):
Este trabalho tem por finalidade reunir informações para que em um local de produção de leite com finalidade econômica se possa ter um produto com o minimo possível de bactérias, não patogênicas para o consumo humano. Descrevemos o desenvolvimento da glândula mamária, porque, é aí que começa o problema do leite: podemos chamá-la de \"Fábrica de leite\", com todos os seus incovenientes. Tomamos a precaução de informar sobre os cuidados higiênicos e mecânicos quando houver a manipulação do úbere para a extração do leite. Ressaltamos as possíveis fontes de contaminação do lei te iniciando com o animal passando pelo meio ambiente, pelo ordenhador, transporte e distribuição. Relacionamos os locais utilizados para o manejo dos animais em produção e as condições higiênicas necessárias para tal. Sobre microrganismos, lembramos os que se desenvolvem no leite e os transformam causando alterações prejudiciais ao produto e os outros que prejudicam os consumidores causando-lhe doenças, algumas muito graves, outras menos graves; mas todas quebrando a higidez do consumidor e por consequência avolumando o rol das doenças notificáveis. Analisamos os componentes do leite, frente a legislação vigente, apresentando uma tabela com a composição do leite das diversas espécies animais. Repassamos as análises químicas e físicas que os regulamentos impõem e apresentamos as recomendações do Ministério da Saúde quanto á flora bacteriana mínima permitida. Os objetivos são bem claros, pois há necessidade de uma assistência sanitária aos criadores, uma orientação aos comerciantes e esclarecimentos às autoridades administrativas, da saúde e educação. As tabelas obtidas com as análises realizadas, demonstram claramente as distorções encontradas nas amostras de leite colhidas nas regiões de Itapecerica da Serra e Juquitiba. A porcentagem de amostras de leite que estariam condenadas somam, para Itapecerica da Serra 76,18% e para Juquitiba 71,72%. Esse quadro dá idéia perfeita de que a produção de leite naquela região está abandonada pelas autoridades responsáveis pela Vigilância Sanitária (Setor Saúde) e pela Defesa Sanitária Animal (Setor Econômico).This paper aims at assembling information in order that the least number possible of non-pathogenic bacteria for human consumption can be achieved in a site designed for a profitable dairy. The development of the mammary gland is described since it is there that the problem of milk begins; it can be called a \"milk-factory\", with all its inconveniences. All precautions are taken to inform about sanitary and mechanical procedures on the process of milk-extraction carried out by ubre handling. Some possible sources of milk contamination are emphasized, beginning with those related to the animal and going on with those originated from the enviroment, the milker, and the milk transportation and distribuition. The most common sites used for managing animals in production are mentioned, as well as the needed sanitary conditions for such end. In what microorganisms are concerned to, we point out the ones which are developed within the milk, transforming it and causing harmfull alterations to the product and others that injure the consumer\'s health causing diseases, some of them very serious, other less serious, but all of them breaking the consumer\'s state of health and, as a consequence, increasing the roll communicable diseases. Milk components are analysed in face of the current legislation with the presentation of a table containing the milk-composition concerning various animal species. A review on the chemical and psysical analyses required by law is made, presenting the recommendations of the Ministry oh Health as to the minimal bacterial flora allowed. The objectives of the paper are rather clear, since there is a need for sanitary assistance on the part of the cattle breeders, orientation to be provided to milk-traders and englightenment to both, the health and education administrative authorities. Data from the analyses carried out clearly demonstrate the distortions found out in milk-samples collected along the Itapecerica da Serra and Juquitiba regions. The percentage of milk-samples which would be condemned by health authorities sums up 76.18% for Itapecerica da Serra and 71.72% for Juquitiba. This picture gives a perfect idea of how the milk-production in that region is left abandonmed by the authorities in charge of the sanitary surveillance (Health sector) and the Animal sanitary Defense (Economic Sector).
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Oliveira, Camilo Ferreira de. "Avaliação da eficacia do "tetra-test" como ferramenta de gestão da qualidade do leite cru refrigerado /". Jaboticabal : [s.n.], 2009. http://hdl.handle.net/11449/94643.
Testo completoAbstract (sommario):
Orientador: Luiz Francisco PrataBanca: Ana Maria Centola Vidal Martins
Banca: Angela Cleusa de Fátima Banzatto de Carvalho
Resumo: Este trabalho teve o objetivo de avaliar a eficácia de uma nova ferramenta de gestão da qualidade do leite cru refrigerado, comparativamente à utilização dos testes tradicionais de controle, nas condições da Instrução Normativa 51 (IN 51). Foram utilizadas 374 amostras individuais de leite cru refrigerado (produtor) e 125 amostras de leite cru de conjunto (bocas de tanques de caminhões transportadores, referindo-se a leites desses mesmos produtores). As amostras foram submetidas a duas análises microbiológicas, sendo as individuais submetidas à prova rápida de redução em tubos - o "Tetra-Test", com o objetivo de estimar a carga microbiana do leite e a microbiota predominante, enquanto as amostras de conjunto foram submetidas à contagem padrão em placas (CPP) como método de referência. Paralelamente, buscou-se verificar os efeitos do processo de centrifugação nas características e/ou propriedades da matériaprima industrial durante a execução do processo por Ultra Alta Temperatura (UAT). Foram utilizadas 56 amostras de leite provenientes da linha de processamento, tomadas imediatamente antes e depois da etapa de centrifugação interposta no início do processo, as quais foram submetidas a ambos os testes microbiológicos ("Tetra- Test" e CPP), além da determinação da variabilidade da composição do leite e determinação do índice proteolítico da k-caseína. O "Tetra-test" se mostrou eficaz na avaliação da qualidade microbiológica do leite cru podendo ser utilizado como uma ferramenta de gestão, uma vez que seus resultados se correlacionaram proporcionalmente aos obtidos pela CPP e possibilitaram informações complementares sobre as características da microbiota dominante, oferecendo vantagens sobre os tradicionais testes de redução. Os resultados mostraram que grande... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This study aimed to evaluate the efficacy of a new tool for quality management of refrigerated raw milk, compared to traditional control tests in accordance to the Brazilian Ministry of Agriculture, Livestock and Food Supply (MAPA) Normative Instruction No. 51. A total of 374 individual samples of refrigerated raw milk (from producers) and 125 samples of bulk raw milk (from milk transport tankers from these same producers) were studied. Samples were submitted to microbiological analyses, being individual samples submitted to rapid reduction in test tubes - the "Tetra-Test", in order to estimate the microbial load of milk and predominant microbiota, while the bulk samples were analyzed by standard plate count as a reference method. At the same time, it was investigated the effects of the centrifugation on the characteristics and/or properties of industrial raw material into the incoming of UHT process. Were analyzed 56 samples of milk from the processing line, obtained immediately before and after centrifugation performed early in the process. Both of them were subjected to microbiological tests ("Tetra-Test" and PCA). In addition it was determined the variability of milk composition and proteolytic rate of k-casein. The "Tetra-test" showed to be effective in assessing the microbiological quality of raw milk and can be used as a management tool, since its results correlated proportionally with those obtained by standard plate count and make possible to obtain more information about predominant... (Complete abstract click electronic access below)
Mestre
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D'Amico, Dennis. "Incidence, Ecology, and Fate of Target Foodborne Pathogens in the Cheesemaking Continuum". ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/63.
Testo completoAbstract (sommario):
Due to renewed interest in specialty cheeses, small-scale artisan and farmstead producers are manufacturing numerous varieties of cheese, including those that present higher risk such as surface-ripened soft cheeses, often using raw milk. The presence of pathogenic bacteria in raw milk on large scale dairy farms is well documented as the dairy farm itself can serve as a reservoir. To assess the risks associated with the use of raw milk in the manufacture of small-scale artisan cheese we evaluated overall milk quality and prevalence of four target pathogens (Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., and Escherichia coli O157:H7) in raw milk from 11 farmstead cheese operations in Vermont. Although overall incidence was low in comparison to other surveys, variation from farm to farm, independent of species, indicates that some operations practice strict hygienic controls and that additional effort is needed on others. Our data also suggest that if present, pathogen population levels in raw milk are extremely low. Although these pathogens are readily inactivated by pasteurization, pasteurized milk and milk products, including soft cheese, have been implicated in major outbreaks of L. monocytogenes infection as the result of post-processing environmental contamination. U.S. Standards of Identity permit the manufacture of these and other cheeses from raw milk, provided they are aged for a minimum of 60 days typically at a temperature no less than 35°F (1.67°C) to provide safety. Of particular concern are the surface-mold-ripened soft cheeses due to the growth potential during aging and refrigerated holding following increases in pH. In a study on the growth potential of L. monocytogenes introduced as post process contaminants on surface-mold-ripened cheeses we demonstrate that holding cheese in compliance with U.S. Federal regulations supports pathogen growth from very low levels regardless of the whether the milk used was raw or pasteurized. Moreover, the 60 day aging rule encourages extended holding which could inadvertently contribute to risk. It is clear that the safety of cheeses within this category must be achieved through control strategies other than pasteurization or aging. Effective environmental monitoring and control of Listeria spp. within processing plants, including farmstead cheese operations, is considered paramount in reducing cross contamination of ready-to-eat foods. To assess the incidence and ecology of Listeria spp. in farmstead cheese processing environments we conducted environmental sampling in 9 different cheesemaking facilities over a 10-week period while comparing three detection/isolation protocols. Results indicate that the use of detection/isolation methods incorporating dual primary enrichment with a repair step allowing for the recovery of injured Listeria enhances detection of Listeria spp., including L. monocytogenes, and that the addition of PCR increases sensitivity of detection while greatly reducing time to results. Our data indicate that the extent of farmstead cheese plant contamination with Listeria spp., notably L. monocytogenes, is comparatively low for dairy processing plants, especially those with contiguous farms and aids in the identification of control points for use in designing more effective control and monitoring programs. Overall the studies contained herein fill data gaps in the literature considering the threat of emerging pathogens in raw milk intended for farmstead cheesemaking, as well as the incidence and distribution of Listeria spp., including molecular subtypes, in small farmstead cheese processing environments over time. These data will help inform risk assessments which evaluate the microbiological safety of artisan cheeses, particularly those manufactured on farms.
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Espinosa, Pesqueira Diana Maricela. "Effect of high hydrostatic pressure processing on biogenic amines formation in artisan caprine and ovine raw milk cheeses". Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/83971.
Testo completoAbstract (sommario):
El objetivo comprendido en esta tesis doctoral fue evaluar el efecto de la aplicación de la Alta Presión Hidrostática (APH) en la formación de Aminas Biogenas (AB) en quesos elaborados a partir de leche cruda. Para este propósito fue necesaria la participación de dos queserías artesanas como proveedoras de las dos variedades de queso elaboradas a partir de leche cruda utilizadas en este estudio, una de leche de oveja y otra de de leche de cabra. La visita a cada una de las queserías se realizó previamente con el fin de conocer las instalaciones, las condiciones de elaboración de los quesos y el grado de cumplimiento de la gestión del autocontrol.
Los quesos fueron ajustados a las dimensiones de la canasta del equipo de APH, envasados al vacío y tratados por APH a 400 MPa de presión, durante 10 min, y 2 ºC de temperatura. Estas condiciones fueron aplicadas a los quesos entre los días 3 y 7 (APH1) y al día 15 (APH15) después de la elaboración. En cada caso se realizaron, durante la maduración, los análisis necesarios para conocer el efecto de cada tratamiento en la microbiología, los parámetros fisicoquímicos, el contenido de AB y las características sensoriales y de textura de los quesos.
Así mismo, se estudió la capacidad formadora de AB en la microbiota presente en cada una de las variedades de queso. Para este propósito se realizó la validación de un método cualitativo para la detección de bacterias con actividad aminoácido decarboxilasa y se evaluó la frecuencia de las diferentes especies y cepas bacterianas encontradas con esta capacidad.
El sistema de higiene y calidad basado en los principios del análisis de peligros y puntos críticos de control (APPCC) observado en cada quesería participante no está propiamente implantado. Sin embargo en ambas queserías se aplica, de diferentes maneras, el programa de pre-requisitos, aunque en algunos casos estos procedimientos y controles no estén por escrito y/o registrados. Los principales puntos débiles encontrados en ambas queserías fueron: El mantenimiento preventivo de instalaciones y equipos; los procedimientos de limpieza y desinfección; y la gestión y eliminación del lactosuero. Adicionalmente, en una de las queserías se observó que el control de la calidad del agua suministrada era inadecuado.
En ambos tipos de queso se observó que la aplicación de APH influyó en el contenido de AB, mostrando una reducción, en comparación con la muestra control, alrededor del 75 y 35% en los quesos con tratamiento APH1 y APH15, respectivamente. La tiramina (TY) y la putrescina (PU) fueron las aminas más afectadas en los quesos elaborados de leche cruda de cabra, mientras que la TY y la cadaverina (CA) lo fueron en los quesos de leche cruda de oveja.
La disminución en la concentración AB en los quesos presurizados al inicio de la maduración pudo deberse a la reducción observada en los recuentos microbianos un día después de la aplicación del tratamiento (principalmente lactococos, lactobacilos, enterococos y enterobacterias), junto con en el descenso del contenido de aminoácidos libres percibido, 34 y 48% menor que el obtenido en los quesos control de leche de cabra y oveja al final de la maduración, respectivamente. Por otro lado, la aplicación del tratamiento APH15 mostró también una reducción significativa en los recuentos microbianos. Sin embargo el contenido de aminoácidos libres observado fue similar a los quesos control.
Los dos medios decarboxilantes, bajo en nitrógeno (LND) y bajo en glucosa (LGD), utilizados en el método cualitativo para la detección de bacterias con actividad aminoácido decarboxilasa mostraron parámetros de diagnostico satisfactorios para la identificación de bacterias con la capacidad de formar PU, CA y TY, siendo su optimo punto de corte fijado entre 10-25 mg L-1, con un área bajo la curva ROC superior al 0,90 y unos valores de sensibilidad y especificidad superiores al 84 y 92%, respectivamente. No obstante, este método mostró menor capacidad en la detección de bacterias con la habilidad de producir HI, siendo considerada, de acuerdo con los parámetros de diagnostico evaluados, como aceptable y deficiente, para los medios LND y LGD, respectivamente.
La mayor actividad aminoácido decarboxilasa observada entre las bacterias aisladas de los quesos de leche de cabra y oveja fue la tirosina decarboxilasa, con una capacidad de producción de TY superior a 100 mg L-1, seguida por la lisina y la ornitina decarboxilasa, con una habilidad de formación de CA y PU en concentraciones de 100-1000 mg L-1 y superiores a 1000 mg L-1, respectivamente. Los principales microorganismos productores de TY mostraron ser aquellos pertenecientes a los grupos de Lactococcus, Lactobacillus, Enterococcus y Leuconostoc, mientras que las cepas bacterianas de Enterobactericeae y Staphylococcus fueron las principales formadoras de CA y PU, aunque algunas cepas de Enterococcus, Lactococcus, Leuconostoc, y Pediococcus mostraron tener capacidad de producir diaminas a niveles superiores de 100 mg L-1.
En lo referente a las características sensoriales y de textura, los quesos tratados con APH muestran una reducción de la fracturabilidad. Este hecho pudo ser debido a los cambios en la microestructura causados por la aplicación de APH y, en el caso de los quesos presurizados, al inicio de la maduración posiblemente también a la disminución en la velocidad de proteólisis producida. Por otro lado, en la evaluación sensorial de la textura, las diferencias significativas percibidas fueron únicamente encontradas en la firmeza de los quesos, siendo consideradas las muestras presurizadas como más firmes que los quesos control. La determinación de color mostró que la diferencia total (ΔE) de las muestras tratadas en comparación con los controles fue mayor después de la aplicación de APH (alrededor de 4.4), sin embargo esta diferencia fue disminuyendo a medida que la maduración avanzaba. Así mismo, la diferencia de color percibida por el panel de evaluación sensorial, fue significativa únicamente en las muestras de leche de oveja con tratamiento APH1.The aim of this work was to evaluate the effect of the High Hydrostatic Pressure (HHP) on the formation of Biogenic Amines (BA) in raw milk cheeses. For this purpose, two Spanish artisan cheese factories were selected to provide the cheeses to be used in the survey. These factories were previously visited to check the compliance with the hygienic standards required by European Regulations. One variety of cheese was chosen from each factory, both made from raw milk. One of them was made from ovine milk and the other from caprine milk. A HHP treatment of 400 MPa during 10 min at 2 ºC was chosen as the most suitable. These conditions were applied at the begging of the ripening between 3rd and 7th day (HHP1) or on the 15th day (HHP15), in each case the effect of the treatments on the microbial, physicochemical, textural, and sensory parameters, as well as on the formation of different BA were assessed during the maturity period. The BA forming capacity of the microbiota present in the cheeses was also evaluated. To this purpose a qualitative screening method to detect the amino acid decarboxylase activity of bacteria was validated and the frequency of the different species and strains with this capacity was determined in either the ovine and caprine raw milk cheeses studied. The hygienic quality system based on the HACCP principles of the two visited artisan cheese factories was not strictly established. However, the prerequisites program was applied according to their necessities, although in most cases the procedures and results of the controls were not appropriately written or registered. The preventive maintenance of the facilities and equipments, cleaning and sanitation procedures, and the whey waste disposal were the main weaknesses found in both cheese factories. Besides, the water supply control was also unsuitable in one of them. Biogenic amine content in both types of cheeses was greatly influenced by HHP. The treatments applied on the beginning and on the 15th day of ripening displayed 75 and 35% lower amounts of BA, respectively, than those obtained in the control untreated samples, being TY and PU the most affected amines in caprine milk cheeses, while TY and CA were so in ovine milk cheeses. The BA reduction in the caprine and ovine HHP1-samples can be explained as a result of a significant decrease of microbiological counts observed one day after the HHP-treatment (specially in the lactoccocci, lactobacilli, enteroccocci and enterobacteria groups) and the slower proteolysis detected in these samples, which showed 34 and 48% less free amino acids than the control caprine and ovine milk cheese samples at the 60th day of ripening, respectively. On the other hand, the HHP treatment applied on the 15th day also resulted in the decrease of microbiological counts, although in this case the liberation of amino acids was not different than the control samples. The amino acid decarboxylase microplate screening method using low nitrogen decaboxylase (LND) and low glucose decaboxylase (LGD) broths had satisfying diagnostic parameters to detect the PU, CA and TY- forming bacteria, being their optimal cut off between 10-25 mg L-1, with an area under ROC curve above 0.90 and a sensitivity and specificity values above 84 and 92%, respectively. Nevertheless, the test had less capacity to detect the HI-forming bacteria. According to the diagnosis parameters evaluated, this test was considered only as acceptable and poor, for LND snd LGD media, respectively. Among the isolates obtained from caprine and ovine milk cheeses with amino acid decarboxylase activity, the TY forming bacteria were the most frequent, showing a strong production (exceeding 100 mg L-1), followed by those with CA and PU-forming ability with strong and prolific production (100-1000 and over 1000 mg L-1, respectively). In the first case, strains belonging to the Lactococcus, Lactobacillus, Enterococcus and Leuconostoc groups were found as the main TY producers, whereas Enterobactericeae and Staphylococcus strains were the main PU and/or CA forming bacteria, although some Enterococcus, Lactococcus, Leuconostoc, and Pediococcus strains showed an ability to produce diamines at levels above 100 mg L-1. The decelerated rate of proteolysis in HHP1 samples, combined with the structural changes caused by the pressure, could contribute to reduce the fracturability of cheeses. However, this decrease could be only due to the formation of a more homogeneous microstructure in the ovine milk cheeses with the HHP15 treatment. The sensory panel noticed that the firmness in the HHP1 and HHP15 samples was significantly different than in control samples. The total color differences (ΔE) in the HHP samples was higher during the first stages of the ripening (around 4.4 in HHP1 and HHP15 samples), decreasing as the sample aged. In addition, differences in color were also perceived by the sensory panel, being significant only in ovine milk cheeses with the HHP1-treatment.
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Leamy, Ryan. "Diversification Activities Of Vermont Dairy Farmers: A Study Of Raw Milk And Local Beef Processing In The State". ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/308.
Testo completoAbstract (sommario):
The vast majority of earned agricultural dollars in Vermont come from the dairy industry, but with volatility in the market in recent years, including rising costs of feed and the fluctuating price of milk, state officials have begun to recommend diversification of farm activities to instill resiliency into the system. The research presented in this thesis explores two avenues for diversification, farm-to-consumer sales of raw milk and local beef production.
The second chapter utilizes diffusion theory to understand the prevalence of raw milk consumption in Vermont, develop a profile of the raw milk consumer, document the motivations of raw milk consumers, and identify sources and channels of information for raw milk consumers. The results of a general population telephone survey indicate that 11.6% of those surveyed reported consuming raw milk and are on average educated, middle-aged, and middle-income earners in small households. Compared to US Census data, there are no demographic differences between raw milk consumers and the average Vermonter. Motivations for consumption include preference for raw milk's flavor, believed health benefits, and knowing or being a farmer. The primary sources of information are dairy farmers, friends, family, and co-workers. The primary channel through which information is obtained is person-to-person discussions. We conclude by discussing the implication of our findings on food protection trends and future research
The third chapter investigates beef processing in the state and through the Agriculture of the Middle paradigm develops a firmographic profile of processors, identifies the frequency of use of a set of industry best practices and articulates the current opportunities and barriers to beef processing. The results of the firmographic profile show that most processors utilize both fee-for-service processing and buy-in processing and that each model is an equal percentage of revenue for business. Most processors indicated clearly demarcated busy and slow seasons with no change in the number of employees during these times and little change in operation capacity. Most processors are involved with some industry best practices and most had at least one anchor client to stabilize their operations. There are opportunities in marketing and opening up new markets but the seasonality, infrastructure and consistency of supply are and may remain a hindrance to this advancement. We conclude that there is little difference between models and that most farmers and processors are already in the stages of developing positive and equitable business relationships and that the future of beef production in Vermont is strong.
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Sanvido, Gustavo Braga 1980. "Efeito do tempo de armazenamento do leite cru e da temperatura de esticagem do leite pasteurizado sobre sua vida de prateleira". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255183.
Testo completoAbstract (sommario):
Orientador: Mirna Lucia GiganteDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-08T22:58:46Z (GMT). No. of bitstreams: 1 Sanvido_GustavoBraga_M.pdf: 1185267 bytes, checksum: f431ac8d0bd92eae958bb8236d2d65bd (MD5) Previous issue date: 2007
Resumo: O objetivo do trabalho foi avaliar o efeito do tempo de armazenamento do leite cru e da temperatura de estocagem do leite pasteurizado sobre sua qualidade físicoquímica, microbiológica e vida de prateleira. Para cada experimento utilizouse 150 litros de leite cru que foram divididos em 3 latões de 50 litros armazenados por 0, 4 ou 7 dias a 5 ± 1ºC antes da pasteurização. Durante o armazenamento refrigerado, amostras de leite cru foram avaliadas quando a presença de resíduos de antibióticos, contagem de células somáticas, pH, acidez, densidade, extrato seco total, gordura, nitrogênio total e solúvel em pH 4,6 e em TCA 24%, coliformes a 3035 ºC e a 45ºC e a contagem dos seguintes microorganismos: aeróbios mesófilos, psicrotróficos, Pseudomonas spp., termodúricos mesófilos e psicrotróficos, esporos mesófilos e psicrotróficos. Após o período de armazenamento refrigerado o leite foi pasteurizado (7275 ºC/1520 segundos), refrigerado (5±1ºC) e envasado em embalagens plásticas de polietileno, as quais foram divididas em dois lotes e estocadas a 5±1ºC ou a 10±1ºC. Durante o armazenamento refrigerado amostras dos leites pasteurizados foram avaliadas para as mesmas características, excetuandose contagem de células somáticas e a presença de resíduos de antibióticos e incluindose os testes de eficiência de pasteurização (peroxidase e fosfatase) e a pesquisa de Salmonela spp. O final da vida de prateleira do leite pasteurizado foi estabelecido como sendo o primeiro dia em que as amostras apresentassem contagem total de microorganismos mesófilos aeróbios superior a 8 x 10 4 UFC/mL. O experimento completo foi repetido três vezes e o delineamento experimental utilizado foi o Splitsplitplot com três fatores. Durante o armazenamento refrigerado do leite cru observouse o aumento significativo da proteólise, da acidez e das contagens de todas as classes de microrganismos avaliadas. A contagem total de microrganismo, cujo valor máximo permitido pela legislação brasileira é 10 6 UFC/ml foi plenamente atendida no dia de recebimento do leite, entretanto atingiu valores de 6,10 x 10 6 e 1,83 x10 8 UFC/ml após 4 e 7 dias de armazenamento refrigerado. Todas as amostras de leite pasteurizado apresentaram teste negativo para fosfatase e positivo para peroxidase e atenderam aos padrões microbiológicos definidos pela Agencia Nacional de Vigilância Sanitária, que estabelece a tolerância indicativa de coliformes 45ºC igual a 4 NMP/mL e ausência de Salmonela spp/25 mL. A contagem inicial de microorganismos mesófilos aeróbios no leite pasteurizado aumentou significativamente com o aumento do tempo de armazenamento do leite cru e foi, em média, de 5,2x10, 1,9 x10 2 e 4,0 x10 2 UFC/mL, para o leite cru armazenado por 0, 4 e 7 dias respectivamente. Além disso, quanto maior a temperatura de estocagem do leite pasteurizado, maior a contagem de microorganismos, que foi, em média, de 1,5x10 2 e 2,8x10 2 UFC/mL para o leite estocado a 5±1 e 10±1ºC, respectivamente. A interação entre os tratamentos afetou significativamente a fase lag de todas as classes de microorganismo estudadas, exceto esporos mesófilos e psicrotróficos. O tempo de fase lag apresentou tendência de ser maior quanto menor o tempo de armazenamento do leite cru (0 dia) e menor a temperatura (5±1ºC) de estocagem do leite pasteurizado. Nesta condição a vida de prateleira do leite pasteurizado foi de 10,7 dias. Quando o leite cru foi armazenado por 7 dias antes da pasteurização e foi estocado a 10±1ºC a vida de prateleira foi apenas de 2,3 dias. Estes resultados confirmam que para aumentar a vida de prateleira do leite pasteurizado é necessário, além da boa qualidade, um curto tempo de armazenamento do leite cru e uma baixa temperatura para a estocagem do leite pasteurizado
Abstract: The objective of this work was to evaluate the effect of raw milk storage time and pasteurized milk storage temperature on milk physical, chemical and microbiological quality and shelf life. For each experiment, 150 liters of raw milk were used, divided into three 50 liter milk cans, stored during 0, 4 or 7 days at 5 ± 1ºC before pasteurization. During refrigerated storage, samples of raw milk were evaluated with respect to the presence of antibiotic residues, somatic cell count, pH, acidity, density, total dry extract, fat, total nitrogen and nitrogen soluble at pH 4.6 and in 24% TCA, total and fecal coliforms and the counts of the following microorganisms: aerobic mesophiles, psychrotrophs, Pseudomonas spp., thermoduric mesophiles and psychrotrophs, mesophilic and psychrotrophic spores. After the refrigerated storage period, the milk was pasteurized (7275 ºC/1520 seconds), refrigerated (5 ± 1ºC) and packaged in polyethylene plastic bags, which were divided into two lots and stored at 5 ± 1ºC or at 10 ± 1ºC. During the refrigerated storage, samples of the pasteurized milks were evaluated for the same characteristics as the raw milk, except for somatic cell count and the presence of antibiotic residues, and including pasteurization efficiency tests (peroxidase and phosphatase) and testing for Salmonella spp. The end of the shelf life of the pasteurized milk was established as the first day in which the samples presented a total count of aerobic mesophilic microorganisms above 8 x 10 4 CFU/mL. The complete experiment was repeated three times and the experimental design used was the Splitsplitplot with three factors. During the refrigerated storage of the raw milk, a significant increase of proteolysis, acidity and counts of all the classes of microorganisms evaluated was observed. The total microorganism count, which was within the limit permitted by the Brazilian legislation of 10 6 CFU/mL on the day of reception, reached values of 6.10 x 10 6 and 1.83 x 10 8 CFU/mL, after 4 and 7 days of refrigerated storage, respectively. All the samples of pasteurized milk presented a negative test for phosphatase and a positive test for peroxidase and attended the microbiological standards defined by the Brazilian Sanitary Vigilance Agency (Agência Nacional de Vigilância Sanitária), that establishes an indicative tolerance for fecal coliforms equal to 4 MPN/mL and the absence of Salmonella spp/25 mL. The initial count of aerobic mesophilic microorganisms in the pasteurized milk increased significantly with the increase of the raw milk storage time and was, in average, of 5.2 x 10, 1.9 x 10 2 and 4.0 x 10 2 CFU/mL, for the raw milk stored for 0, 4 and 7 days, respectively. Furthermore, the higher the pasteurized milk storage temperature, the higher the microorganism count, that was, in average, of 1.5 x 10 2 and 2.8 x 10 2 CFU/mL for the milk stored at 5 ± 1 and 10 ± 1ºC, respectively. The interaction between the treatments significantly affected the lag phase of all the classes of microorganisms studied, except for mesophilic and psychrotrophic spores. The lag phase period presented a tendency to be greater for shorter raw milk storage times (0 day) and lower pasteurized milk storage temperatures (5 ± 1ºC). In this condition, the shelf life of the pasteurized milk was 10.7 days. When the raw milk was stored for 7 days before pasteurization and stored at 10 ± 1ºC, the shelf life was only 2.3 days. These results confirm that to increase the shelf life of pasteurized milk, apart from good quality, a short raw milk storage time and a low pasteurized milk storage temperature are necessary
Mestrado
Mestre em Tecnologia de Alimentos
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Murta, Paulo Henrique Grassano. "Níveis residuais de cádmio em amostras de leite \"in natura\" coletadas em usina de beneficiamento na cidade de Ribeirão Preto". Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/6/6135/tde-16022018-112910/.
Testo completoAbstract (sommario):
Amostras de leite \'in natura\'coletados de diferentes latões foram analisadas por espectrofotometria de absorção atômica com forno de grafite, para determinação dos níveis residuais de cádmio, tendo sido selecionados latões com pontos de solda(L1), latões velhos(L2) e latões reestanhados(L3), perfazendo um total de 59 amostras, sendo o seguinte os valores médios encontrados: Latões com pontos de solda: 0,0169 ppm Latões velhos: 0,0168 ppm Latões reestanhados 0,0118 ppm Não foram encontradas diferenças significativas nos níveis residuais de cádmio considerando-se os diferentes tipos de latões, tendo-se efetuado o teste de Significância entre duas médias a um nível de garantia de 95 %. Os valores absolutos estiveram entre 0,0500 ppm e 0,0020 ppm de cádmio. Avaliaram-se os valores residuais de cádmio, considerando-se apenas a origem do leite, ou seja a propriedade rural, tendo-se observado valores médios variando de 0,0080 ppm a 0,0272 ppm. Foram encontradas diferenças significativas entre os níveis residuais de cádmio nas amostras de leite levando-se em conta a origem do produto. Coletaram-se amostras de leite de 05 animais diretamente na propriedade rural, e o valor médio encontrado foi de 0,01738 ppm, mais elevado do que a média encontrada nos diferentes latões. Pelos valores determinados por outros autores em diferentes países, quando comparados com os resultados da presente pesquisa, pode-se supor que os níveis aqui detectados, embora dentro dos padrões da legislação brasileira, podem estar elevados, colocando em risco a saúde de crianças e pessoas debilitadas, tendo em vista o potencial do metal pesado se acumular no organismo, causando-lhe danos irreversíveis. O autor sugere maiores pesquisas sobre os níveis residuais de metais pesados em órgãos de animais abatidos, utilizados na alimentação humana e na fabricação de rações animais. Sugere ainda pesquisas abrangentes nos adubos fosfóricos utilizados nas plantações e levantamentos epidemiológicos nas populações rurais que consomem produtos diretamente das propriedades onde ocorrem as contaminações. Não foram encontradas as fontes de contaminação do leite, porém vários autores asseveraram que pode estar ocorrendo uma contaminação natural de plantas e animais decorrentes do uso de produtos contaminados com metais pesados, podendo ainda ser uma contaminação casual e até do próprio solo, contaminado pelo cádmio.A total of 64 samples of raw milk collected in a processing plant were analysed for the determination of cadmium levels, using the Atomic Absorption Spectrophotometry attached to a Carbon Rod atomizer.The cans used for milk transportation were selected as follow: soldered cans, older cans and tinned cans. The mean average of cadmium levels in milk sanples were: soldered cans- 0,0169 ppm, older cans- 0,0168 ppm tinned cans 0,0118 ppm There were no statistical differences amongst the cadmium levels in milk from different cans. The cadmium levels in milk were analysed to verify the statistical differences amongst the sites of production, and the mean values ranged from 0,0272 ppm to 0,0020 ppm. Statistical differences in cadmium levels related to the different sites of production were found. Samples of cows milk were collected and analysed for cadmium determination, and mean average level was 0,01738 ppm., higher tham the mean average levels from different cans. The mean cadmium values from this issue , and the values reported by other authors in papers ,allow us to say that probably the cadmium levels found in milk samples might be hight specially for children and older persons. These levels may be a Public Health hazard to those who consume products from animal sources The author suggests that more issues to determine the metal levels in animal organs consumed by the population and used for animal feedstuff should be made. In attempt to an epidemiological study in the population that uses milk and others products from farms, more studies should be made. Sources of milk contamination were not found, and authors claimmed that these metals are present in plants and soil with an unknown origin, probably due to environmental contamination.
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Sarrazin, Pascale. "Effects of feeding raw and roasted sunflower seeds on ruminal fermentation, nutrient utilization and milk production of dairy cows". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80873.
Testo completoAbstract (sommario):
Three studies were conducted to determine the effects of roasting on ruminal degradability of sunflower seeds and the effects of feeding roasted sunflower seeds on ruminal fermentation, nutrient digestibility and milk yield and composition of dairy cows. Experimental treatments were a control diet with no added sunflower seed, a raw sunflower seed diet and a roasted sunflower seed diet. Sunflower seed diets contained 6% fat whereas the control diet contained 3% fat. In study one, two ruminally fistulated cows were used in a randomized complete block design to determine the effects of roasting on ruminal degradation of sunflower seeds. In the second study, three ruminally cannulated lactating Holstein cows were used in a 3 x 3 Latin square experiment to determine the effects of dietary treatments on ruminal fermentation and total tract nutrient utilization. In the last study, three primiparous and six multiparous Holstein cows were used in three 3 x 3 Latin squares to determine the effects of dietary treatments on milk yield and composition.
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Komani, Nosiphiwo. "Molecular characterization of the Mycobacterium tuberculosis complex (MTC) of raw milk from selected dairy farms in the Eastern Cape". Thesis, University of Fort Hare, 2013. http://hdl.handle.net/10353/d1013157.
Testo completoAbstract (sommario):
Tuberculosis (TB) is an ancient infectious disease that has been infecting different populations around the globe and it has also been considered as one of the most successful human and animal disease. TB found in animals such as cattle and other known bovids is known as bovine tuberculosis. Bovine tuberculosis (BTB) is an infectious disease found in cattle mainly caused by Mycobacterium bovis. M. bovis is a member of the Mycobacterium tuberculosis complex (MTC) together with M. tuberculosis, M. africanum, and M. canetti where the natural host is humans; whereas M. caprae, M. microti and M. pinnipedii usually have animals as their natural host. In this study the molecular characterization of the MTC from cow milk in the Eastern Cape was investigated. One hundred and twenty samples (40 ml each) were collected from three dairy farms in the Eastern Cape, South Africa. These samples were processed using a modified Petroff decontamination method. Sample processing was followed by DNA isolation using a Zymo Bacterial/Fungal DNA Kit and the amplification and detection of the MTC was done using the Seeplex MTB Nested ACE assay. The drug susceptibility tests were done using GenoTypeMTBDRplus assay which detects mutations and resistance to INH (isoniazid) and RMP (rifampicin). The milk isolates were further analyzed using a spoligotyping method which is based on the PCR amplification of a highly polymorphic direct repeat locus in the M. tuberculosis genome which detects and types the MTC. A percentage of 20.8 % samples were found to be positive for MTC using the Seeplex MTB Nested ACE assay. There were 42.1 % samples that were resistant to both INH and RMP with the rest sensitive to either INH or RMP. The spoligotyping method showed that 78.3 % samples resembled Family 33 strains and the rest (21.7 %) resembled a spoligotyping signature known to be that of M.africanum. Both these strains belong to the Ancestral lineage with Indo-Oceanic and West Africa 2 lineage. The outcomes of our study showed that molecular methods for detection of MTC can be applied directly on milk samples without the need for culturing.
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Oliveira, Gabriela Capriogli [UNESP]. "Pesquisa de Listeria monocytogenes no leite bovino de conjunto de propriedades de agricultura familiar". Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151855.
Testo completoAbstract (sommario):
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A refrigeração é um importante método de conservação do leite, porém quando ocorre por longo período, a qualidade desse produto pode ser alterada devido, principalmente, a multiplicação de bactérias psicrotróficas. Dentro desse grupo de micro-organismos, entre os gêneros patogênicos, destaca-se Listeria monocytogenes. A identificação deste patógeno em alimentos é de interesse não somente pelos efeitos nocivos aos animais, mas também pelos efeitos na saúde humana. O objetivo do presente estudo foi investigar a presença de L. monocytogenes em 95 amostras de leite bovino de conjunto de pequenas propriedades leiteiras de agricultura familiar. As amostras de leite foram cultivadas nos meios seletivos de PALCAM e ALOA e as colônias características foram avaliadas por métodos fenotípicos e moleculares, pela Reação em Cadeia da Polimerase (PCR), para detecção de L. monocytogenes. Apesar dos resultados negativos no cultivo e na PCR, a patogenicidade de L. monocytogenes para os animais e os riscos em saúde pública, justificam estudos continuados para vigilância epidemiológica do agente em produtos de origem animal como o leite.
Refrigeration is an important milk preservation method. However, milk quality may deteriorate if the product is refrigerated for long periods, mainly due to the growth of psychrotrophic bacteria. This group of microorganisms includes pathogenic genera, most notably Listeria monocytogenes. The detection of this bacterium in food is important, given its pathogenic effects on human and animal health and also its economic relevance. This study focused on detecting the presence of L. monocytogenes in milk samples collected at small family-owned dairy farms. Samples were cultivated on PALCAM and ALOA agars for microbiological analysis and a molecular analysis by polymerase chain reaction (PCR) was performed for the detection of L. monocytogenes. Despite the negative results obtained in both these analyses, further studies are recommended to confirm or refute the negligible effect of L. monocytogenes on small dairy farms.
FAPESP: 2015/11571-4
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Oliveira, Gabriela Capriogli. "Pesquisa de Listeria monocytogenes no leite bovino de conjunto de propriedades de agricultura familiar". Botucatu, 2017. http://hdl.handle.net/11449/151855.
Testo completoAbstract (sommario):
Orientador: Helio LangoniResumo: A refrigeração é um importante método de conservação do leite, porém quando ocorre por longo período, a qualidade desse produto pode ser alterada devido, principalmente, a multiplicação de bactérias psicrotróficas. Dentro desse grupo de micro-organismos, entre os gêneros patogênicos, destaca-se Listeria monocytogenes. A identificação deste patógeno em alimentos é de interesse não somente pelos efeitos nocivos aos animais, mas também pelos efeitos na saúde humana. O objetivo do presente estudo foi investigar a presença de L. monocytogenes em 95 amostras de leite bovino de conjunto de pequenas propriedades leiteiras de agricultura familiar. As amostras de leite foram cultivadas nos meios seletivos de PALCAM e ALOA e as colônias características foram avaliadas por métodos fenotípicos e moleculares, pela Reação em Cadeia da Polimerase (PCR), para detecção de L. monocytogenes. Apesar dos resultados negativos no cultivo e na PCR, a patogenicidade de L. monocytogenes para os animais e os riscos em saúde pública, justificam estudos continuados para vigilância epidemiológica do agente em produtos de origem animal como o leite.
Abstract: Refrigeration is an important milk preservation method. However, milk quality may deteriorate if the product is refrigerated for long periods, mainly due to the growth of psychrotrophic bacteria. This group of microorganisms includes pathogenic genera, most notably Listeria monocytogenes. The detection of this bacterium in food is important, given its pathogenic effects on human and animal health and also its economic relevance. This study focused on detecting the presence of L. monocytogenes in milk samples collected at small family-owned dairy farms. Samples were cultivated on PALCAM and ALOA agars for microbiological analysis and a molecular analysis by polymerase chain reaction (PCR) was performed for the detection of L. monocytogenes. Despite the negative results obtained in both these analyses, further studies are recommended to confirm or refute the negligible effect of L. monocytogenes on small dairy farms.
Mestre
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Tsegmed, Uranchimeg. "Staphylococci isolated from raw milk of yak and cattle in Mongolia : studies on the occurrence, characterization, detection of enterotoxin and antimicrobial susceptibility profile of the isolates /". Uppsala : Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/10186505.pdf.
Testo completo
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Linde, Susanna Gezina. "Die ontwikkeling van 'n moniteringsprogram vir roumelkgehalte as deel van die gehaltebestuurstelsel van 'n melkprosesseerder in die Noordwes-provinsie". Thesis, Bloemfontein: Central University of Technology, Free State, 2008. http://hdl.handle.net/11462/264.
Testo completoAbstract (sommario):
Thesis (M. Tech.) -- Central University of Technology, Free State, 2008In this study, the development and implementation of a quality-monitoring program for raw milk as part of the quality management system of a milk processor was studied. Various aspects that contribute to raw milk quality were also included. Ten factors that are important in the production of good quality raw milk were summarised in the Ten Point Plan for the production of quality raw milk. Thirty-eight producers, who have supplied raw milk to the processor over a period of five year, were involved in this program. The producers are located all over the Northwest Province. Sixty thousand litres of milk is processed at the processor daily. The milk is taken in from the farms on alternative days by tankers supplied by the processor. A mark sheet was developed to evaluate control points during milking that can be measured directly from the laboratory. This was done monthly. Factors that could not be measured in the laboratory were evaluated when visits to the milk parlours were done twice a year. At the end of the year, the results of the mark sheet as well as the results of the parlour audits were compiled on a quality chart and the results were calculated as a percentage. The processor used the results of the quality charts to reward producers for quality milk. It was found that producers do not have the necessary infrastructure and knowledge to analyse milk. Analysing the raw milk and releasing the results to the producer are important measures to identify and manage problem areas that can pose a risk to the production of good quality raw milk. It is very important to supply the producer with the correct and relevant information because most of the representatives of companies, which visit the farms, supply information to the benefit of the product they sell. A formal monitoring program ensures that raw milk adhere to quality measures due to the fact that producers know the basic principles necessary for the production of good quality raw milk and the fact that the producer can implement measures in his/her own unique farm environment. The implementation of the Ten Point Plan for the production of quality raw milk at the processor had a significant influence on the quality of raw milk that was bought from producers. During times of milk shortages, the processor had to buy milk from alternative sources, which have no quality-monitoring program. Most of the times, this milk did not comply with the law regarding the total bacterial count, the coliform count, and the E. coli count. Record keeping is an important part of the management system of a dairy. Results from this study stressed a meaningful relationship between the keeping of records as mentioned in the Ten Point Plan and the production of good quality raw milk. It is recommended that producers be sharpened regarding the requirements for the production of good quality raw milk. Purchasing good quality raw milk assured the marketing of the best quality dairy products to the consumer. The contribution of this study to the dairy industry is the fact that the implementation of a quality-monitoring program ensures the maintenance of a sustainable quality of raw milk to the industry.
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Schmidt, Verena Sophia Johanna [Verfasser], Siegfried [Akademischer Betreuer] Scherer, Matthias A. [Gutachter] Ehrmann e Siegfried [Gutachter] Scherer. "Microbiota of raw and microfiltered ESL milk / Verena Sophia Johanna Schmidt ; Gutachter: Matthias A. Ehrmann, Siegfried Scherer ; Betreuer: Siegfried Scherer". München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1175582603/34.
Testo completo
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Helling, Alexander Paul. "Sustainable Agriculture in Vermont: Economics of Climate Change Best Management Practices and the Complexity of Consumer Perceptions of Raw Milk". ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/437.
Testo completoAbstract (sommario):
Changing weather patterns, the declining social fabric of rural communities, and economic uncertainty increasingly pose challenges to Vermont communities. The socially and environmentally embedded production practices within sustainable agriculture present a potential solution to these problems. In order to make the most of the potential benefits of these practices society must maximize their adoption. This requires an understanding of both farmer adoption of these practices and consumer perceptions of the resulting food products. This thesis contributes two original articles on sustainable agriculture through the analysis of factors driving both farmer adoption and consumer perceptions of products and practices often thought of as sustainable.
The first article seeks to understand farmer adoption of climate change best management practices (CCBMPs). Farmer perceptions of risk and profitability of best management practices (BMPs) are key determinants of adoption, which traditional incentive programs like the Environmental Quality Incentives Program (EQIP) attempt to address by providing financial and technical support. To ensure appropriate price points are offered through these programs, regional price structures must be based upon locally established costs. Thus, this article focuses on the economic cost of implementing and maintaining CCBMPs for twelve diverse farms in Vermont. Specifically, three CCBMPs for Vermont are examined: cover cropping, management intensive rotational grazing (MIRG), and riparian buffer strips. Results of a yearlong farmer based data collection process indicate that the average cost for cover cropping is $129.24/acre, for MIRG is $79.82/acre, and for a tree based riparian buffer strip is $807.33/acre. We conclude that existing incentive payments for cover cropping and MIRG are below costs, likely resulting in under-adoption.
The second article reports on a study which seeks to understand the factors influencing Vermont consumer perceptions of raw milk safety. While this article makes no assertion regarding the sustainability of raw milk, an association is established between the motivations for raw milk consumption and sustainable agriculture support. Vermonterâ??s appear to be continuing the trend of consuming raw milk at an increasing rate despite continued declarations from local and national public health officials that raw milk is too microbiologically dangerous to justify its consumption. Thus this study was designed to increase understanding of the factors driving consumer perceptions of raw milk safety. A conceptual model was developed to establish potential factors and related questions were incorporated into the 2014 Vermonter Poll. Resulting data were analyzed using a Probit regression analysis. We conclude that observable factors have the greatest influence on perceptions of raw milk safety. Specifically, perceived health benefits, presence of children in the household, and taste all influence perceptions of raw milk safety.
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Wasserstrom, Vicky Marie. "Subsequent milk production and metabolic response of first-calf heifers fed whole raw soybeans during the last trimester of gestation". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07112009-040303/.
Testo completo
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Harper, Nigel Murray. "Comparing the mannitol-egg yolk-polymyxin agar plating method to the three tube most probable number method for enumeration of bacillus cereus spores in raw and high-temperature-short-time pasteurized milk". Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1683.
Testo completo
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Weigel, Michele. "Avaliação da contaminação por aflatoxina M1 em leite cru e leite UHT". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/11140.
Testo completoAbstract (sommario):
A aflatoxina M1 (AFM1) é um metabólito tóxico resultante da biotransformação da aflatoxina B1 e pode ser secretada no leite de animais que ingerem alimentos contaminados com esta última. Considerando os efeitos adversos que podem ocorrer devido à ingestão do produto contaminado e visto que as crianças, maiores consumidoras deste alimento, são potencialmente mais sensíveis que os adultos aos efeitos desta micotoxina, a avaliação da presença de AFM1 no leite se faz necessária. Durante o período de março a novembro de 2006 foram analisadas 48 amostras de leite cru provenientes de 8 propriedades fornecedoras de leite para uma Cooperativa de Leite da Serra Gaúcha e 80 amostras de leite UHT, provenientes de 7 marcas distintas, comercializadas em Porto Alegre (RS). A metodologia empregada na análise de aflatoxina M1 envolveu partição líquido-líquido na etapa de extração, uso de coluna de sílica gel na etapa de purificação e Cromatografia em Camada Delgada para a detecção. O limite de detecção foi de 10 ng e a avaliação da eficiência do método apresentou valor de 86% no teste de recuperação. Nas condições de trabalho e pelo método utilizado nenhuma das amostras analisadas foi positiva para a presença de AFM1, sugerindo que as mesmas encontram-se dentro das conformidades legais.Aflatoxin M1 (AFM1) is a toxic metabolite resulting of the biotransformation of aflatoxin B1, and may be sectreted in milk of animals that consume foods contaminated with aflatoxin B1. Considering the adverse effects that can occur when foods contaminated are consumed, and since children, the greatest milk consumer are potentially more susceptible than adults to the effects of this mycotoxin, the evaluation of the presence of AFM1 in milk is necessary. From March to November of 2006 48 samples of raw milk from 8 dairy farms that integrate a Milk Cooperative of mountain region of Rio Grande do Sul and 80 samples of UHT milk from 7 different brands commercialized in Porto Alegre were analized. The mehodology employed for the analysis of aflatoxin M1 involved liquid-liquid partition on the extraction step, use of silic gel column for the purification step and Thin Layer Chromatography for the detection. The evaluation of the method efficiency present a value of 86% in the recovery test and the detection level was 10ng. Following analysis conditions and the method employed none of the samples analyzed were positive for the presence of aflatoxin M1, suggesting that samples analysed attend the legal conformities.