Dissertations / Theses on the topic 'Microbial load'

Effect of high hydrostatic pressure (150-200-250 MPa) on the microbial load and quality parameters (pH, color, 5-hydroxymethylfurfural-HMF) of white (Sultaniye) and red (Alicante Bouschet) grape juices with combination of temperature (20-30-40&deg<br>C) and holding time (5-10-15 min) was studied. Increased pressure and temperature showed significant effect on microbial reduction in white and red grape juices (p&lt<br>0.05). The effect of pressure and time on pH drop was found to be insignificant (p&gt<br>0.05). HHP resulted in E&lt<br>1 for white grape and E&lt<br>7 for red grape juice samples. Shelf life analysis for HHP treated white grape juice (200 MPa-40&deg<br>C-10min) and red grape juice (250 MPa-40&deg<br>C-10min) revealed no microbial growth up to 90 days when stored at 25&deg<br>C. Although HMF formation was observed in industrially manufactured, pasteurized samples (65&deg<br>C for 30 min), no HMF was detected in HHP treated white and red grape juices. HHP at the suggested conditions can be recommended as a better production alternative to heat treatment for white and red grape juice with respect to microbial load and studied quality parameters even at temperatures lower than required for pasteurization.

Microbial load can be controlled using either synthetic or natural preservatives. Particular interest has been focused on the potential application of plant essential oils as safer additives for meat. However, there is no published research on the use of essential oils during the meat drying process. This study was focused on enhancing the meat drying process. At first a value-added dried meat product by using oregano essential oil (OEO) to inhibit the growth of bacteria, and the sensorial response from assessors is presented. It was found that the application of the OEO in meat is effective in inhibiting Salmonella enteritidis and Escherichia coli. After 6 hours of drying at 55°C, 2 ml (0.038 ml l-1 air) and 1.5 ml (0.028 ml l-1 air) of OEO were considered the minimal inhibitory concentrations (MICs) against S. enteritidis and E. coli, respectively. Samples treated with 0.75 ml of OEO were more attractive for consumption compared with the control; at a higher concentration of OEO, the sensory quality of the food was affected. Next, the effect of modified blanching treatments on the drying behaviour of beef meat was evaluated by determining moisture ratio versus time curves and the influence on sensory quality of the resulted product. The 3 treatments under investigation were (1) oil treatment (2) steam blanching and (3) hot air blanching with 3 doses of oregano essential oil (1) 1.5 ml (2) 3 ml and (3) 6 ml. Each treatment had an effect on the drying time of the beef samples, however, the dose of oregano essential oil applied did not affect the drying process. The results showed that steam blanching was very effective reducing the drying time. Meanwhile, 1.5 ml and 3 ml hot air blanching samples and 1.5 ml oil treatment samples were judged as better from sensory point of view and the respondents considered that adding oregano essential oil enriched the pleasantness of the smell. In conclusion, a value-added dried meat product obtained by using oregano essential oil to enhance food safety received an acceptable sensorial response from consumers. Additionally, each modified blanching treatment tested influences the drying kinetics process, but the dose of oregano applied did not affect the drying process. In this sense, hot air blanching and oil treatment with the lowest dose had an acceptable sensorial response from consumers.

Dissertação de Mestrado Integrado em Medicina Veterinária<br>Insect consumption has been increasing worldwide, particularly in industrialized countries. Insect-based ingredients are considered novel foods in Europe, which raises some concern regarding the food safety of these products. Gut emptying by starvation prior to killing is perceived as an effective practice in the reduction of the microbial load of insects but can lead to weight loss and consequently a profit reduction to the farmers. The purpose of this study was to evaluate the fat loss of crickets (Acheta domesticus) starved for 0h, 24h and 48h, and their corresponding microbial loads (total aerobic counts (TAC) and Enterobacteriaceae). Gram stains were also performed for the colony-forming units (CFU) from TAC. The effect of sex on the microbial numbers was assessed, having not been found significant differences (p=0.72 and p=0.46 for TAC and Enterobacteriaceae, respectively). TAC increased (p=0.002) by almost 1 log CFU/g in the 48h starvation group. Only the 24h starvation group showed a significant decrease (p=0.004) in Enterobacteriaceae counts of 1 log CFU/g. The Gram stains showed changes in the microbiological composition of samples collected at 24 and 48h. Gram-positive cocci predominated at 24h but decreased at 48h (from 68 to 48%). Bacilli were only detected at 24h (8%). The fat content did not decrease significantly, neither at 24h (p=0.13 for males and p=0.13 for females) nor at 48h (p=0.57 and p=0.98 for males and females, respectively). Starvation for 24h was efficient in reducing the microbial load of raw crickets without significant fat loss. A longer starvation period promoted a higher microbial load, possibly due to modulation observed in the microbial diversity.<br>RESUMO - Impacto do jejum na matéria gorda e teor microbiano presente no grilo doméstico (Acheta domesticus) utilizado para alimentação humana - O consumo de insetos tem vindo a aumentar globalmente, particularmente em países industrializados. Ingredientes à base de insetos são considerados novos alimentos na Europa, o que suscita alguma preocupação em matéria de segurança dos alimentos destes ingredientes. O esvaziamento do trato gastrointestinal através de jejum antes do abate é visto como uma prática eficaz na redução do teor microbiano presente nos insetos, mas pode, no entanto, levar a perda de peso considerável e, consequentemente, à redução de lucro para os produtores. O objetivo deste estudo foi avaliar a perda de gordura no grilo doméstico (Acheta domesticus) quando submetido a períodos de jejum de 0h, 24h e 48h, e correspondentes teores microbianos (Aeróbios totais (AT) e Enterobacteriaceae). Foram ainda feitas colorações de Gram a partir das unidades formadoras de colónia (UFC) das placas de AT. O efeito do sexo na carga microbiana foi avaliado, não tendo sido encontradas diferenças significativas (p=0.72 e p=0.46 para AT e Enterobacteriaceae, respetivamente). A contagem de AT aumentou (p=0.002) em cerca de 1 log UFC/g no grupo de jejum de 48h. Apenas o grupo submetido a jejum por 24h mostrou um decréscimo significativo (p=0.004) nas contagens de Enterobacteriaceae na ordem de 1 log UFC/g. As colorações de Gram mostraram alteração da composição microbiana das amostras colhidas às 24 e às 48h, com predominância de cocos Gram-positivos às 24h e redução às 48h (de 68 para 48%). Foram detetados bacilos apenas no grupo 24h (8%). Não houve redução significativa do teor de gordura nem às 24h (p=0.13 em machos e p=0.13 em fêmeas) nem às 48h (p=0.57 e p=0.98 em machos e em fêmeas, respetivamente). A aplicação de um período de jejum de 24h foi eficaz na redução da carga microbiana de grilos crus sem redução de gordura significativa. Um período de jejum mais prolongado promoveu um teor microbiano mais elevado, possivelmente devido à modulação da diversidade microbiana.<br>N/A

Thesis (MSc Food Sc)--Stellenbosch University, 2015.<br>ENGLISH ABSTRACT: Many South African farmers are forced to use water from nearby rivers for crop irrigation, since it is the most affordable and sometimes only source of water available to them. During this research project, a baseline study was performed on a farm irrigating fresh produce with water obtained from the Eerste River. The baseline study was done over a five month period, at six preselected sampling points, to determine the microbial and physico-chemical parameters of the water so a baseline could be established to compare the results to when the ultraviolet (UV) apparatus was installed (February 2013). Aerobic colony count (ACC), total coliforms (TC) and Escherichia coli (E. coli) were tested for during the microbiological study, while the physico-chemical analysis comprised of temperature, pH, conductivity, chemical oxygen demand (COD), alkalinity and total soluble solids (TSS). The UV treatment study was also performed over a five month timeline, at eight different sampling points (original six sampling points, with additional sampling points before and after UV). The same microbiological tests were performed during the UV treatment study, but turbidity and percentage ultraviolet transmittance (% UVT) were performed additionally during physico-chemical analysis. During the baseline study ACC, TC and E. coli counts as high as 9 600 cfu.mL-1, 13 799 MPN.100 mL-1 and 2 098 MPN.100 mL-1 were isolated at the river (Sampling Point 1), respectively. While performing the UV treatment study ACC, TC and E. coli counts as high as 142 000 cfu.mL-1, 241 960 MPN.100 mL-1 and 6 867 MPN.100 mL-1 were isolated at the river, respectively. As a result it was concluded that the Eerste River was mostly unsuitable for irrigation of fresh produce that are consumed raw. The higher counts in the river, during the UV treatment study might be attributed to the increase in rainfall that occurred in the sampling months (March to July 2013). The counts as measured at the point of irrigation are considered of greater importance, since the counts present in the river might still decrease to below the guideline levels after passing through sand filters and the addition of hydrogen peroxide (current mode of treatment) or after passing through the UV in the UV treatment study. The ACC, TC and E. coli counts during the baseline study were as high as 8 800 cfu.mL-1, 24 196 MPN.100 mL-1 and 85 MPN.100 mL-1 at the point of irrigation (Sampling Point 6), respectively. After hydrogen peroxide addition average logreductions ranging between 0.65 and 1.13 were seen, but reduction was never constant. The counts at the point of irrigation remained more or less constant compared to the river due to contamination that occurred at the sand filters, making the water unsuitable for irrigation of fresh produce in terms of ACC and TC counts. In the UV treatment study ACC, TC and E. coli counts were as high as 35 000 cfu.mL-1, 10 462 MPN.100 mL-1 and 63 MPN.100 mL-1 at the point of irrigation (Sampling Point 8), respectively. Average log-reductions in the range of 0.90 to 1.25 were achieved, but it was inconsistent. After treatment with chlorine and re-sanding of the sand filters, no further contamination occurred and counts decreased to below guideline limits, making the water safe for irrigational use in terms of all of the microbiological parameters. Not only is UV treatment more effective in reducing microbiological counts than H2O2, it is also relatively less expensive in the long term. Hydrogen peroxide treatment of water amounts to a very high capital expense every month, whereas UV may seem expensive when starting up, but the monthly operating cost thereafter is marginally less than for H2O2. It is of great importance to farmers to find a treatment that would reduce the counts in the river water to below the guideline limits required for safe irrigation since pathogens can be carried over from water onto fresh produce, resulting in an increase in produce-associated foodborne outbreaks and loss of consumer trust.<br>AFRIKAANSE OPSOMMING: Menigte Suid-Afrikaners is afhanklik van nabygeleë riviere om hulle oeste te besproei aangesien dit meestal die mees bekostigbare en soms enigste bron tot hul beskikking is. Tydens hierdie projek is ‘n grondslag sowel as ‘n UV behandelingsmetode studie uitgevoer op ‘n plaas wat vars vrugte en groente besproei met water water wat hul vanuit die Eersterivier verkry. Die grondslagstudie is oor ‘n tydperk van vyf maande uitgevoer by ses voorafgekose punte. Dit is gedoen om die mikrobiologiese sowel as chemiese parameters van die water te bepaal sodat ‘n grondslag beskikbaar kon wees om met resultate te vergelyk wat met behulp van die ultravioletmasjien verkry is (in Februarie 2013 geïnstalleer). Tydens die mikrobiologiese studie is daar vir aerobiese koliform tellings (ACC), totale koliforme (TC) en Escherichia coli (E. coli) getoets. Tydens die chemiese analise is temperatuur, pH, konduktiwiteit, chemiese suurstof benodiging, alkaliniteit en totale oplosbaie vastestowwe in die water getoets. Die UV behandelingsmetode studie is ook oor ‘n tydperk van vyf maande uitgevoer, met twee addisionale toetspunte by. Presies dieselfde mikrobiologiese analises as wat tydens die grondslag studie uitgevoer is, is tydens die UV behandelingsmetode studie uitgevoer, maar vir die chemiese analise het turbiditeit en persentasie ultraviolet transmissie van die water bygekom. Gedurende die grondslag studie was ACC, TC and E. coli tellings so hoog as 9 600 cfu.mL-1, 13 799 MPN.100 mL-1 en 2 098 MPN.100 mL-1 onderskeidelik uit die rivier geïsoleer (Punt 1). Tydens die UV behandelingsmetode studie was ACC, TC en E. coli tellings so hoog as 142 000 cfu.mL-1, 241 960 MPN.100 mL-1 en 6 867 MPN.100 mL-1 onderskeidelik by die rivier geïsoleer. Gevolglik is daar afgelei dat die Eersterivier se water meestal ongeskik is om te gebruik vir die besproeiing van vars groente en vrugte wat rou geëet word sonder dat enige verdere behandeling plaasvind. Die hoër tellings wat tydens die UV behandelingsmetode in die rivier sigbaar was kan hoofsaaklik toegeskryf word aan die toename in reënval in daardie tyd (Maart tot Julie 2013). Tellings soos gemeet by die punt van besproeiing is wel van groter belang as die wat aangeteken is by die rivier; aangesien die tellings wat in die rivier aangeteken is steeds kan afneem tot onder aanvaarbare hoeveelhede soos in die standaarde uiteengesit, want die water moet steeds deur sandfilters beweeg en word ook huidiglik deur waterstofperoksied behandel tydens die die grondslagstudie of beweeg deur die UV apparaat in die UV behandelingsmetode studie. Die ACC, TC en E. coli tellings soos gemeet by die besproeiingspunt (Punt 6) was so hoog as 8 800 cfu.mL-1, 24 196 MPN.100 mL-1 en 85 MPN.100 mL-1, onderskeidelik. Na waterstofperoksied byvoeging was die gemiddelde log-reduksies sigbaar, tussen 065 en 1.13, maar afnames was nooit konstant nie. Die tellings by die punt van besproeiing het ongeveer konstant gebly in vergelyking met die tellings wat by die rivier aangeteken is; moontlik as gevolg van die hoë kontaminasie vlakke in die sandfilters. Kontaminasie van sandfilters het veroorsaak dat die water ongeskik was vir die gebruik van besproeiing van vars groente as gevolg van die hoë ACC en TC vlakke. Tydens die UV behandelingsmetode studie is ACC, TC en E. coli tellings so hoog as 35 000 cfu.mL-1, 10 462 MPN.100 mL-1 en 63 MPN.100 mL-1, onderskeidelik aangeteken (Punt 8). Gemiddelde log-reduksies tussen 0.90 tot 1.25 was verkry, maar behandeling en afnames in tellings was nie konstant nie. Nadat die sandfilters met chloor behandel is en die sand daarin vervang is, het geen verdere kontaminasie by die punt voorgekom nie. Nadat al die voorafgenoemde behandelings afgehandel is, het die tellings tot laer as die van die standaarde gedaal en dus was die water nou veilig om te gebruik vir besproeiingsdoeleindes in terme van die mikrobiologiese parameters. Die UV behandelingsmetode is nie net meer effektief in die verlaging van mikrobiologiesese tellings as waterstofperoksied nie, dis ook heelwat goedkoper in die langtermyn. Waterstofperoksied behandeling van water lei tot ‘n baie hoë kapitale onkoste per maand, terwyl UV baie duur mag voorkom in die beginfase, maar die maandelikse kostes is aansienlik laer as die van waterstofperoksied en maak sodoende op daarvoor. Dit is van uiterste belang vir boere om ‘n water behandelingsmetode te vind wat die hoë tellings in die rivier sal afbring tot laer as Suid-Afrikaanse en Kanadese riglyne; aangesien patogene oorgedra kan word van vars vrugte en groente. Laasgenoemde kan tot ‘n drastiese toename in vars voedsel geassosieerde siektes en gevolglik ‘n afname in die vertroue wat ‘n kliënt in ‘n produk plaas, lei.