Dissertations / Theses on the topic 'Frozen fish'

In the present study the effects of characteristic freezing times and storage time at -22°C on the quality of the adductor muscle of post-rigor scallops (Pecten maximus)and gilthead seabream fillets (Sparusa urata) were studied in regard to the integrity of muscle structure, myofibrillar protein denaturation and aggregation, lipid degradation, texture and sensory changes. This information would be useful for achieving optimal conditions for freezing these species and assessing their quality during frozen storage for commercial purposes. Scallop muscles and gilthead seabream fillets were frozen individually with characteristic freezing times that can be met in commercial practice of freezing seafoods. After freezing, the samples were thawed and their quality was evaluated. Fresh samples were analyzed as controls. Intermediate characteristic freezing times (i. e. 89 and 49 minutes for scallop muscles and 74 minutes for gilthead seabream fillets) caused more damage to cell structure of both species than the shorter and longer characteristic freezing times tested. Short characteristic freezing times (i. e. 19 minutes for scallop muscles, and 2 and 18 minutes for gilthead seabream fillets) reduced the thawing losses of both species compared to the longer characteristic freezing times (. e. 235 to 1000 minutes for scallop muscles, and 640 minutes for gilthead seabream fillets) tested. Freezing at short characteristic freezing times produced raw fillets similar in texture to the fresh fillets. Therefore, short characteristic freezing times (equal to or less than 19 minutes) are beneficial for freezing both species. Scallop muscles and gilthead seabream fillets were kept frozen for up to 301 and 340 days, respectively. Sampling was carried out at regular intervals on fresh and stored frozen samples. Storage time affected the integrity of infra-cellular organelles, reduced the water holding capacity, caused structural changes to myofibrillar proteins and affected the sensory attributes of both species. Frozen scallop muscles were in acceptable eating condition after a storage period of ten months, with most of the changes in bio-chemical and physical properties being pronounced after three months of storage. Based on the changes in taste scores versus storage time, it was assessed that the practical storage life of frozen gilthead seabream fillets was circa 5 to 6 months Cat+-ATPase activities for scallop muscles and a linear model that combines free fatty acids, peroxide values and protein content in centrifugal tissue fluids for gilthead seabream fillets, may be reliable methods for industry to use for assessing their quality during long term storage at -22°C.

High-pressure (HP) depresses the phase-transition point of water especially in the case of ice-I (down to -21°C at about 210 MPa). This phenomenon has several potential advantages in food processing applications, such as pressure shift freezing (PSF) and HP thawing. However, scientific knowledge available in this area is still relatively limited. The main objectives of this research were to investigate the phase-transition behavior of foods under pressure processing in the context of PSF and HP thawing techniques and to evaluate their impact on product quality.
Distilled water and fresh pork muscle were tested by a HP differential scanning calorimeter (DSC) using isothermal pressure scan (P-scan) and isobaric temperature scan (T-scan). P-scan tests showed that the phase-transition temperature (T) of pork was a function of the weighted-average pressure (P¯1--2): T = -1.17 - 0.102P¯1--2 - 0.00019 P&d1;21-2 (R2 = 0.99) that was much lower than that of pure ice. The phase-change latent heat of pork was estimated by P-scan. T-scan indicated the phase-transition point at a constant pressure, but it showed less accurate than P-scan. The ratio (Rice, %) of ice crystals formed by rapid release of pressure (P) was evaluated using the HP DSC: Rice-water = 0.115P + 0.00013P2 (R2 = 0.96) for water, and Rice-pork = 0.084P + 0.00012P2 (R2 = 0.95) for pork muscle. In the developed method, the pressure-dependent thermal properties of test materials are not required.
A preliminary study on ice-crystal formation was carried out using small gelatin gel samples frozen by conventional air freezing (CAF), liquid immersion freezing (LIF) and PSF at different pressures. The ovoid structure left from ice crystals was evaluated for area, equivalent diameter, roundness and elongation. The diameter (mean +/- S.D.) was 145 +/- 66, 84 +/- 26, 91 +/- 30, 73 +/- 29, and 44 +/- 16 mum for the treatments of CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. Roundness and elongation did not show a clear trend with different freezing tests. Similar experiments using small-size Atlantic salmon (Salmo salar) resulted in the diameter of 110 +/- 41, 17 +/- 8.4, 16 +/- 8.8, 8.2.5 and 5.0 +/- 2.1 mum for CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. The roundness was 0.38 +/- 0.14, 0.55 +/- 0.21, 0.57 +/- 0.18, 0.63 +/- 0.14 and 0.71 +/- 0.14 for the above treatments, respectively. (Abstract shortened by UMI.)

Myofibrillar proteins, the main components that impart functional properties to muscle foods, can undergo denaturation and aggregation during frozen storage. The overall objective of this research was to study the changes in protein structure that are associated with the preparation and frozen storage of surimi. In addition, the relative cryoprotective effects of whey protein concentrate, whey protein isolate, soy protein isolate, flaxseed meal and flaxseed protein were assessed in surimi during storage.
Raw surimi was prepared by repeatedly washing Alaska pollock flesh with chilled water. The product was either slowly frozen or underwent rapid freezing using liquid air; in either case it was then subjected to frozen storage at -20°C for 24 months. Protein structural changes were monitored using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), native-PAGE, Fourier transform infrared/attenuated total reflectance (FTIR/ATR) spectroscopy, and differential scanning calorimetry (DSC).
FTIR/ATR spectroscopy showed that during preparation of surimi the alpha-helix content increased with increased number of washing cycles. DSC results revealed a shift in the thermal transition of actin to a higher temperature during surimi preparation. All electrophoresis, FTIR/ATR spectroscopy and DSC results revealed a loss of myofibrillar proteins from surimi after three washing cycles, suggesting that three washing cycles were adequate to prepare surimi.
Native-PAGE showed no major changes in surimi after 24 months storage at -20°C. SDS-PAGE showed relatively minor changes in protein subunit structure with some loss of the myosin light chains (MLC); myosin heavy chain (MHC), actin and tropomyosin were found to be relatively stable. FTIR/ATR spectroscopy indicated a significant decrease in alpha-helix relative to beta-sheet structure in surimi after 2 years of storage at -20°C. The loss of alpha-helical content was more significant in slowly frozen surimi compared to rapid-frozen surimi samples. DSC results revealed a shift in the thermal transition of actin to lower temperatures during frozen storage of surimi.
Changes in the ratio of alpha-helix to beta-sheet structures suggested that flaxseed protein was the most effective cryoprotectant, followed by whey protein isolate and soy protein isolate, for maintaining protein structure stability during frozen storage. Whey protein concentrate and flaxseed meal showed the least cryoprotective ability. After 15 days storage at 4°C, the SDS-PAGE results showed that flaxseed protein was the only cryoprotectant that prevented the degradation of myosin heavy chain, actin and myosin light chains.

The spoilage pattern of carp (Cyprinus carpio) fillets was investigated. The studies were aimed at evaluating the potential use of pressure-shift freezing to reduce quality deterioration during frozen storage. The effects of pressure treatment at low temperature on fish carp fillets were evaluated and conditions were chosen to reduce any adverse effect on the quality of fish fillet. Pressure-shift freezing treatment was applied to carp fillets and biochemical properties were evaluated and correlated with objective measurement of texture, drip loss and the size of ice crystals formed. Changes in these properties were monitored during frozen storage for a period of 75 days.
Results indicated that proteolityc changes due to endogenous enzymes in fish muscle play an important role in quality deterioration of carp fillets during ice storage. No changes were observed in Ca2+-ATPase, Mg2+-ATPase or Mg2+-EGTA-ATPase activity of actomyosin from carp fillets during iced storage (p > 0.05). In contrast, Mg2+-Ca2+-ATPase and Ca2+ sensitivity of actomyosin decreased during ice storage of fish fillets. No changes were found in the SH content of actomyosin throughout the ice storage of carp fillets (p > 0.05). The surface hydrophobicity of actomyosin and auto-degradation products increased during the storage period (p < 0.05).
Response surface methodology (RSM) was used to study the effect of high-pressure treatment on some physico-chemical properties (actomyosin extractability, Ca2+-ATPase activity, surface hydrophobicity, TBA value, liquid loss and firmness) of intact fish fillets. Balancing the benefits of low temperature pressurization with the denaturing effects of pressure on fish proteins, it is evident that there is a region in which the responses of the factors (protein extractability, Ca2+-ATPase activity and protein hydrophobicity) to the processing variables (time and pressure) seemed to be adequate to keep protein denaturation to a minimum. This region lies between 140--175 MPa and 16--18 min. However, it was observed that high-pressure treatment induced changes in colour on fish fillets. The L*, a* and b* values increased as pressure and time treatment increased.
The application of pressure-shift freezing or air-blast freezing resulted in decrease in myofibrillar and sarcoplasmic protein extractability, and reduced actomyosin Ca2+-ATPase activity during frozen storage. However, actomyosin Ca2+-ATPase activity in pressure-shift frozen samples remained relatively higher than that of air-blast frozen samples. On the other hand, levels of thiobarbituric acid and free fatty acids were relatively lower in samples frozen by PSF. The freezing procedure did not seem to have a significant effect (p > 0.05) on the texture of carp fillets. The ice crystals found in PSF fish samples were mainly intracellular, smaller and more regular shaped than those found in the ABF samples, which were mainly extracellular. Differential scanning calorimetry showed that PSF treatment appeared to be more effective in preventing protein denaturation in post-rigor fish fillets than in the pre-rigor fish fillets.

Frozen storage has long been used as a means to slow down the microbial and enzymatic degradation of fish. Unfortunately, over time frozen fish will lose protein solubility and water holding capacity leading to declining quality. To minimize the degradation of frozen fish, cryoprotectants (often a blend of sucrose and sorbitol) are employed. Although successful in limiting protein denaturation and aggregation, sugar based cryoprotectants are not suitable for diabetics or those who dislike sweet tasting fish products. A possible alternative is fish protein hydrolysate (FPH). Current knowledge on the use of FPH as a cryoprotectant, however, is limited. It is necessary to determine how FPH production parameters can be optimized for cryoprotection. It is also necessary to determine the optimal dosage of FPH in fish mince, and how FPH affects the taste of frozen fish products. In this study, response surface methodology was used to optimize processing variables, namely pH, % enzyme/substrate, and hydrolysis time for production of cryoprotective FPH. The optimization study revealed higher cryoprotective efficacy in all 20 FPH samples produced according to a central composite rotatable design compared to a sucrose/sorbitol cryoprotective blend; however, there was little difference among FPH samples. Based on these findings, it is suggested to produce FPH with 1% enzyme/substrate, 1-hour hydrolysis and no pH adjustment because these are the most economical conditions within the central composite rotatable design. FPH produced at the suggested conditions was added to cod fish mince at levels of 2, 4, 6, and 8 percent (w/w). Evaluation of expressible moisture, cook loss, salt extractable protein, and differential scanning calorimetry profiles showed no significant difference between unfrozen and freeze/thawed fish mince samples when containing at least 4 percent FPH. Sensory evaluation by trained panelists showed that the addition of FPH into fish ball products increased the fishiness, saltiness, bitterness, and firmness while decreasing the level of moistness. Panelist comments suggested a taste preference of fish products containing FPH over fish products containing sucrose/sorbitol. Based on the cryoprotective effectiveness and taste acceptability of FPH, it can be concluded that FPH is a viable alternative to sugar based cryoprotectants.

Alterations in the protein and lipid components of lean fish species were studied to elucidate the nature of protein denaturation in Gadus morhua and Melanogrammus aeglefinus during frozen storage. Frozen storage of lean fish, Gadus morhua and Melanogrammus aeglefinus led to the formation of ice crystals, which contributed to protein denaturation. Ice crystals were larger in fish fillets stored at -10°C compared to matching fillets stored at -30°C as studied by light microscopy at -20°C, which indicated damaged muscle fibre by compression. Protein denaturation was also attributed to the effect of lipid oxidation products. The presence of oxygen in the muscle system and high, hydrolytic enzyme and lipoxygenase activity led to increased free fatty acids and lipid oxidation respectively. The peroxide value (PV), conjugated dienes, thiobarbituric acid reactive substances (TEARS) and olefinic to aliphatic protons ratio by 1H NMR spectroscopy was indicative of oxidative deterioration of the lipid components of Gadus morhua and Melanogarmmus aeglefinus during frozen storage especially at -10°C. The ratio of the C=C to the aliphatic groups as assessed by FT-Raman spectroscopy also decreased progressively over the frozen storage period. The 1H NMR, conjugated diene and FT-Raman spectroscopic measurements were found to be effective and less labour intensive techniques for finger printing lipid oxidation than traditional methods. Intact muscle analysis using differential scanning calorimetry (DSC) showed that protein components of the muscle were denatured resulting in altered Tm and DeltaH values. FT-Raman spectroscopy of fish tissue confirmed changes in the proteins and showed decreased levels of alpha-helix and increased ?beta-sheet content (%) as well as changes in hydrophobic groups after frozen storage. These changes were pronounced in samples stored at -10°C compared to samples stored at -30°C. Model systems of protein-lipid complexes were studied using DSC, FT-Raman spectroscopy and ELISA. The effect of lipids and the primary and secondary oxidation products altered the conformation of myosin, collagen and water soluble proteins during freezing and frozen storage. DSC parameters namely Tm and DeltaH values indicated the degree of denaturation of fish proteins, when frozen in the presence and absence of lipids. It is proposed that ice crystal formation resulted in the removal of the hydration shell of the proteins and the overall rearrangement of the stabilising forces; this allowed protein-lipid interaction to take place and induced further protein denaturation. Reduced immune affinity of the myosin-lipid systems towards the myosin antibody compared to the control native myosin indicated conformational changes of the myosin molecule. The addition of lipids (DHA, EPA, extracted fish oil and hexanal) induced secondary structure changes in myosin over and above those caused by freezing. This was evidenced by decreased alpha-helix content with a concomitant increase of beta-sheet structure, indicating myosin polymerisation. A decrease in the tryptophan band, and increase in the ratio of the dityrosine bands indicated changes in hydrophobic groups. The model studies and the analysis of intact fish muscle of Gadus morhua and Melanogrammus aeglefinus suggest that protein denaturation occurred due to the concerted action of ice crystals, supercooled water molecules (unfrozen), high solute concentration, free fatty acids, and primary and secondary lipid oxidation products on the fish muscle proteins. Possible intervention schemes include, the addition of appropriate antifreeze glycoproteins, cryoprotectants and antioxidants.

The object of this thesis was to investigate the role of two different harvest protocols on the post mortem physiology of Chinook salmon, and associated deteriorative processes that occur during frozen storage of the white muscle tissue. The two different harvest methods employed, termed 'rested' and 'exercised', were selected because of the contrasting levels of activity of the animal prior to, and upon, slaughter. While the latter represents conventional harvest techniques Rested and exercised harvesting protocols produced tissue in significantly different physiological states. Immediately post harvest, rested tissue maintained high metabolic energy stores of ATP and glycogen within the tissue, with low concentrations of tissue and plasma lactate. Exercised tissue exhibited near depleted concentrations of ATP and glycogen and a marked metabolic acidosis and lactate accumulation. When frozen immediately post harvest, rested white muscle tissue stored at -19℃ showed no significant changes in these metabolite concentrations over a six month period of profiling. However, during storage of rested tissue at -9℃, hydrolysis of ATP and glycogen with no coincident increase in lactate was observed. No significant changes in metabolite levels were observed within exercised tissue stored at -19 and -9℃, owing to the lack of metabolic energy stores. Transfer of tissue from frozen (-80 and -19℃) to chilled (-1 and +4℃) temperatures witnessed a rapid depletion of tissue ATP and glycogen stores, with rapid increases in tissue lactate concentrations. This metabolic activity was more significant in rested tissue owing to the larger concentrations of metabolic energy stores. This metabolic activity was identified to occur between the temperatures of -3 and -1.5℃ and occurred abruptly (i.e. ATP concentrations depleting in less than one hour) in time. During frozen storage (-19℃ and -9℃), harvest treatment had no significant effect on lipid oxidation processes. However, rested tissue showed a significant ability to retard lipid oxidation processes once removed from frozen storage and placed at chilled temperatures. Throughout six months storage at -19℃ storage, harvest treatment had a significant effect on the rate of protein denaturation as rested tissue consistently held higher concentrations of soluble protein over the storage period. No significant effect was observed between treatments in the rate of protein denaturation during one month frozen (-19℃) then chilled (+4℃) storage. In a supplementary frozen (-80℃) then chilled (-1℃) storage experiment, post mortem storage of rested, whole fish, at chilled (+5℃) temperatures prior to white muscle excision and freezing, was compared to rested and exercised tissue in which the white muscle had been excised and then frozen immediately post harvest. In this experiment rested tissue exposed to a 6 or 24 hour post mortem chilled storage period demonstrated significant retardation of lipid oxidation processes when compared to rested white muscle tissue that was excised and frozen immediately post harvest. Further comparison of the six and 24 hour post mortem stored tissue showed a significant increase in lipid oxidation products after 21 and 24 days chilled storage, respectively. Comparison of results from the six and 24 hour post mortem storage experiment were bordering on significance (p=0.083), warranting further investigation on the effect of post mortem storage of rested tissue on lipid oxidation processes.

The antioxidant properties of various blends of rosemary extract and tocopherols, either alone or with citric and ascorbic acid, were compared in filleted, headed and gutted, and minced rainbow trout (Oncorhynchus mykiss). The filleted and headed and gutted products were stored at -29 degrees C for twelve months, while the minced was stored at the same temperature for 24 weeks. Oxidation was measured by following changes in thiobarbituric reactive substances, conjugated diene hydroperoxides, texture, drip loss, pH, sensory evaluation, and gas chromatographic detection of aldehydes. Natural antioxidants, in particular those that contained citric and ascorbic acids, were effective at retarding the development of conjugated diene hydroperoxides and malonaldehyde (p<0.05). Furthermore, sensory evaluation indicated that treated samples were less oxidized. In subsequent studies, however, it was determined that the herbal flavor notes associated with natural antioxidants complicated the ability of the experienced panel to judge extent of oxidation. Also, using filleted samples, further consumer sensory panels indicated that after 12 months frozen storage, the treated and control samples were equally acceptable. For both the filleted and headed and gutted samples, no texture differences were noted over storage time or between control or variable treatments. When using natural antioxidant products, drip loss and pH were found unreliable predicators of oxidation or muscle degradation.
Master of Science

Introdução - O pescado é amplamente utilizado para a produção de alimentos à base de matéria-prima de origem animal. Nas últimas décadas, inovações tecnológicas possibilitaram o aumento na comercialização de pescado na forma de filé congelado, tornando o controle de temperatura durante a cadeia de produção essencial para a manutenção da sua qualidade. A importação de pescado, inclusive da Polaca do Alasca, vem crescendo ano a ano, sendo os supermercados e hipermercados, da Região Metropolitana de São Paulo, responsáveis por 49,0 por cento de toda a demanda nacional. Objetivos - Avaliar as condições higienicossanitárias de pescado congelado e embalado exposto à venda em gôndolas de supermercados da Grande São Paulo, de acordo com a legislação vigente. Métodos - A pesquisa foi desenvolvida com base em duas abordagens: estudo de campo e laboratorial. Foram selecionados 30 supermercados de 4 municípios da região da Grande São Paulo para aplicação de checklist de avaliação das condições higienicossanitárias do produto e dos equipamentos de exposição e para a coleta de amostras, no período de 7 a 29 de setembro de 2013. Foram coletadas 30 amostras, sendo cada amostra constituída por 3 embalagens de 1 kg de filé de Polaca do Alasca congelado de uma mesma marca, lote, data de fabricação e validade; representando 3 kg por amostra e totalizando 90 kg de produto analisado. Uma parte das amostras, 30 embalagens de 1 kg, foi acondicionada em caixas isotérmicas com temperatura controlada e encaminhada ao laboratório da Faculdade de Medicina Veterinária e Zootecnia da USP para realização das análises microbiológicas (Staphylococcus coagulase positiva e Salmonella spp). As demais 60 embalagens de 1k foram encaminhadas, sob as mesmas condições, ao laboratório do Instituto de Pesca para realização das análises físico-químicas (pH, N-BVT e N-TMA) e sensoriais (colorimetria e textura). Resultados - As principais não conformidades encontradas no checklist, em ordem decrescente, foram: presença de cristais de gelo (100,0 por cento ) e temperatura abusiva dos produtos acima de -12°C (100,0 por cento ); ausência do carimbo do SIF (83,3 por cento ); falta de veracidade na temperatura indicada no termômetro do equipamento (66,6 por cento ) e presença de restos de alimento no fundo dos equipamentos (50,0 por cento ). As análises físico-químicas para o N-BVT e N-TMA; e, as análises microbiológicas para pesquisa de Salmonella spp em 25 gramas e contagem de Staphylococcus coagulase positiva indicaram 100,0 por cento de conformidade com a legislação vigente. A totalidade das amostras apresentou-se não conforme para o parâmetro pH, com medições que variaram de 6,86 a 8,57. Nas análises sensoriais encontraram-se valores de firmeza do filé de 9,02 a 2,52 N, com uma média de 5,3 ± 1,6 N e a colorimetria indicou que os filés de Polaca do Alasca encontravam-se escurecidos e amarelados. Conclusão - A aplicação do checklist indicou deficiências na manutenção da temperatura e na operação das gôndolas de exposição, não proporcionando as condições ideais para a manutenção do pescado congelado durante o seu armazenamento. Embora os resultados das análises microbiológicas tenham demonstrado que os produtos estivessem próprios para o consumo, as análises físico-químicas, em específico os parâmetros referentes ao pH, não estavam de acordo com os valores determinados pela legislação vigente.
Introduction - Fish products are widely used for food production based on raw material of animal origin. In the last decades, technological innovations enabled a raise in the commercialization of frozen fish fillets that turned the temperature control throughout the food chain into essential for its quality maintenance. The import trade of fish products, amongst them the Walleye Pollock, is increasing year after year, being the supermarkets and hypermarkets of São Paulos Metropolitan Region responsible for 49,0 per cent of all Brazilian imported fish products demand. Objective - To evaluate the hygienic-sanitary conditions of packaged frozen fish exposed for sale in supermarkets of Greater São Paulo in accordance with legal regulations. Methodology - This study was based upon two approaches: case study research and laboratory analysis. It was selected 30 supermarkets of four counties of the Greater São Paulo region for the evaluation of products and equipments hygienic-sanitary conditions by the application of a specific checklist and sample collection, from 7 to 29 September 2013. It was collected 30 samples, which one comprised of 3 - 1 kg packages of Walleye Pollock frozen fillets from the same brand, batch number, manufacturing and expiration date, representing 3 kg by sample and totaling 90 kg of analyzed product. A share of these samples, 30 - 1 kg packages, was accommodated and transported in temperature-controlled isothermal box to the Faculty of Veterinary Medicine and Animal Science of USP laboratory for the microbiological (Coagulase positive Staphylococci and Salmonella spp) analysis. The other 60 - 1kg packages were sent, under the same conditions, to the Fishery Institute for physico-chemical (pH, N-BVT and N-TMA and sensory (colorimetry and texture) analysis. Results - The non-compliance acts more frequently observed in the checklist, in descending order, were: presence of ice crystals (100,0 per cent ) and abusive temperature above - 12°C (100,0 per cent ) of the products, absence of SIF imprint (83,3 per cent ); lack of truthfulness in the temperature indicated on the equipment thermometer (66,6 per cent ) and presence of food remains at the bottom of the equipment (50,0 per cent ). The physico-chemical analysis for N-BVT and N-TMA; and, the microbiological analysis for Salmonella spp/25 g and the coagulase positive Staphylococci counts indicated 100,0 per cent of compliance with legal regulations. The totality of the samples were inadequate for the pH parameter, with measurements ranging from 6,86 to 8,57. The sensory analysis shown values of fillet firmness of 9,02 to 2,52 N, in an average of 5,3 &177; 1,6 N and the colorimetry indicated that the walleye pollock fillets were darkened and yellowish. Conclusion - The checklist results pointed out to deficiencies in controlling the temperature and freezers operations and did not offer the ideal conditions to frozen fishs quality maintenance throughout its storage. Although the microbiological analysis results showed that the frozen fish fillets were appropriate for consumption, the physic-chemical analysis, particularly the pH parameters, were not in accordance with values indicated in the current regulation.

É muito elevado o potencial de utilização do pescado na forma de minced fish - MF, servindo de matéria-prima para outros produtos. O MF de sardinha foi avaliado quanto ao rendimento, ao efeito da lavagem sobre a melhoria da cor, à caracterização química e quanto à estabilidade química e sensorial durante estocagem sob congelamento de -17 a -18°C. O rendimento do MF de sardinha lavado com água foi de 55% em relação ao peixe inteiro e próximo do rendimento teórico da parte comestível. A lavagem do MF com água ou água + bicarbonato de sódio proporcionou a obtenção de um produto com cor vantajosamente mais clara e apreciável. Com relação à composição química básica o MF de sardinha lavado com água apresentou maior hidratação e menor teor de cinzas em relação ao controle e semelhantes quantidades de proteína e lípides. Comparado ao controle, o MF de sardinha lavado com água, não apresentou diferença quanto ao perfil de ácidos graxos e pH, o que não ocorreu com o nitrogênio das bases voláteis - N-BVT, que diminuiu, e às substâncias reativas ao ácido tiobarbitúrico - TBARS, que aumentaram. O MF de sardinha lavado com água, contendo ou não antioxidantes artificialmente adicionados, apresentou estabilidade química e sensorial quando mantido sob congelamento, com base nos parâmetros pH, N-BVT, TBARS, odor a ranço e cor, em até 26 semanas de estocagem. Os resultados do presente trabalho são favoráveis à possibilidade de obtenção de MF de sardinha lavado com água e seu emprego como matéria-prima para outros produtos pesqueiros.
The potentiality of fish\'s utilization as minced fish - MF is very high, actually turning into a raw material to other products. The sardine\'s MF was evaluated according to its yield, the washing effect improving the color, its chemical characteristic and chemical and sensorial stability, during frozen storage under -17,-18°C. The yield of sardine\'s MF washed in with water, was 55% related to the whole fish and close to the theoretic yield of eatable portion. The MF\'s washing in water or in water plus sodium bicarbonate provide a product with clearer and more desirable color. Related to the chemical basic composition, sardine\'s MF washed in water, presented better hydration and lower ashes contents than its control, and similar quantity of protein and lipids. Compared to the control, the sardine\'s MF washed in water, had not presented any difference related to the fatty acids profile and pH, that had not happened with the nitrogen of volatile bases - N-BVT, which had been decreased, and the thiobarbituric acid reactant substances - TBARS, that had been increased. The sardine\'s MF washed in water, containing or not added antioxidants, was chemical and sensorial stable when maintained frozen, based on parameters as pH, N-BVT, TBARS, rancidity odor, and color, stored for 26 weeks. The results of this work are propitious to the possibility of achieving sardine\'s MF washed in water, and your utilization as a raw material to others seafoods.

A carne mecanicamente separada (CMS) de pescado é um produto obtido a partir de uma única espécie, ou mistura de espécies de peixes através do processo de separação mecanizada da parte comestível. O bagre africano (Clarias gariepinus) é produzido principalmente nos países africanos e europeus e recentemente foi introduzido na Índia, China e Brasil, destinados exclusivamente ao consumo. O objetivo deste trabalho foi obter e caracterizar a CMS de bagre africano e avaliar sua estabilidade durante o armazenamento a -18°C. Foi determinado o rendimento do processo de obtenção da CMS e a estabilidade foi acompanhada por seis meses com relação a aspectos microbiológicos e físico-químicos (TBARS, BVT, pH e drip), de três tratamentos (A - CMS sem lavar, B - CMS com uma lavagem e C - CMS com duas lavagens). No início e após 90 e 180 dias de armazenamento sob congelamento, as CMS foram utilizadas para elaboração de fishburgers, os quais foram avaliados microbiológica e sensorialmente. A lavagem promoveu mudanças na composição centesimal da CMS, principalmente o aumento do teor de umidade e diminuição dos teores de proteína bruta. Durante o período de estocagem, as CMS mantiveram-se estáveis independentemente da lavagem. Foi observado rendimento da CMS, de aproximadamente 50% em relação ao peixe inteiro. A CMS com duas lavagens apresentou maior umidade (84,26%) que as CMS com uma lavagem (78,52%) e sem lavar (78,42%), ocorrendo também perda de proteína, lipídeos e cinzas, pela lixiviação desses compostos. Os teores de BVT mantiveram-se estáveis durante o período de armazenamento diferindo apenas entre os tratamentos, sendo que a CMS sem lavar apresentou maior valor médio (15,79 mg BVT/100g) que as CMS com uma (5,46 mg BVT/100g) e duas lavagens (2,61mg/100g). No dia zero, o maior valor de TBARS foi encontrado na CMS sem lavar (0,216 mg malonaldeído/kg), ao passo que nas CMS com 1 e 2 lavagens os valores foram respectivamente de 0,083 e 0,099 mg malonaldeído/kg, indicando que a lavagem causou lixiviação da maior parte dos compostos responsáveis pela oxidação lipídica. A legislação brasileira não indica um limite de oxidação lipídica avaliado pelo método de TBARS para CMS de pescado, porém os valores encontrados no final do período de estocagem (0,405; 0,511 e 0,420 mg malonaldeído/kg) para as CMS sem lavar, com 1 e 2 lavagens respectivamente são baixos e indicam pouca oxidação. Os parâmetros microbiológicos da CMS e do fishburger se mantiveram de acordo com a legislação brasileira. Os fishburgers foram muito bem aceitos pelos provadores e o fishburger elaborado com CMS com uma lavagem foi melhor avaliado quanto à aceitação global. As pequenas alterações ocorridas durante o período de armazenamento não afetaram a qualidade da CMS, indicando viabilidade para formulação de produtos com CMS estocada congelada por 180 dias. O processamento de bagre africano na forma de CMS pode ser uma alternativa para aproveitamento de uma espécie sub-utilizada, gerando produtos da piscicultura com valor agregado.
Minced fish (CMS) is a product obtained from only or sereral fish species through the mechanical separation of edible section. African catfish is produced mainly in African and european countries and recently was introduced in India, China and Brazil, destined exclusively to comsumption. The aim of the present study was obtain and characterize the african catfish minced and evaluate the stability during the period of storage under -18°C. Minced fish process yield was determinated and the stability was measured for six months concerning microbiological and physico-chemical analysis (TBARS, BVT, pH and drip), from three treatments (A CMS unwashed, B CMS washed once and C CMS washed twice). The beginning and after 90 and 180 days of frozen storage, the CMS was utilized for preparation of fishburger, that was evaluated for microbiological and sensorial analysis. The CMS washing process promoted changes in centesimal composition, mainly the increase of the moisture and decrease of total protein. During the storage period, the CMS kept the stability apart of washing process. The minced fish process yield was approximately 50% respecting whole fish. The CMS washed twice showed higher moisture (84,26%) than the CMS washed once (78,52%) and CMS unwashed (78,42%), occuring waste of protein, lipid and ash, by washing. During the storage, the BVT kept stable, disagree between the treatments, and the CMS unwashed exhibit higher mean value (15,79 mg BVT/100g) than CMS washed once (5,46 mg BVT/100g) and CMS washed twice (2,61mg/100g). At the zero day, the bigger value of TBARS was determinated in CMS unwashed (0,216 mg malonaldeído/kg), but in CMS washed once and twice, the values was 0,083 e 0,099 mg malonaldeído/kg respectively, signify that the washing process induced removal the majority part of compounds responsible by the lipidic oxidation. The Brazilian legislation do not indicate a limit of CMS lipid oxidation evaluated by TBARS method, however the values at the end of the storage (0,405; 0,511 e 0,420 mg malonaldeído/kg) for CMS without, with one and with two washing are low and indicate low oxidation. The CMS and the fishburger microbiological parameters kept agreed with Brazilian legislation. The fishburgers was accepted by the samplers and the fishburger elaborated with CMS washed once was better evaluated to general acceptability. The changes occured during the period of storage have not affect on CMS quality, indicating availability to products formulated by CMS with 180 days of frozen storage. The CMS process of african catfish can be a alternative to employment of a specie under-utilized, creating aquaculture products with aggregated value.

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia
The "Food Safety" concept makes sense when human being is aware that what ingests must be innocuous for his health and well-being. To give an answer to this global concern, food industry needs guidelines for safe food production. Consequently, Food Safety Management System (FSMS) Standards appeared. This specific work takes in to account the complexity and advantages of these standards implementation, and identifies improvement opportunities and strengths in an industry of frozen fish products, which intends to substitute its DS 3027E:2002 Certification for NP EN ISO 22000:2005. In studied FSMS, the most significant changes that this Company must accomplish are validation activities implementation and control measures characterization. An HACCP study was done accordingly to NP EN ISO 22000:2005 requirements and to a new hierarchical hazards structure, resulting three critical control points. Besides the industry intends to remove both Critical Control Points corresponding to fish washing water and fish glazing water production stages, that will be possible only if they increase chlorine content in supplied water to the factory, at reception level.

碩士
國立臺灣大學
農業機械工程學系研究所
87
The thawing process of frozen fish is indeed a major factor that affects the quality of the flesh of the fish. In order to compare the difference of the thawing curve of different thawing methods, in this research, we use different temperature and velocity of the flow of high humidity air and running water, to thaw the flesh of tunny, then compare the difference between them; we discover that temperature and velocity of the thawing medium are important factors which affect the thawing curve of the frozen fish in thawing. This study also use the finite difference method to build a math model in heat transfer of the thawing of frozen fish. Because the process of melting involve a moving boundary problem, we use enthalpy method to analyze that in the model, and utilize this model for simulating the thawing curve of frozen fish when thawing. A result show that numerical modeling can simulate resembling the thawing curve of real experiment; we can simulate and predict the thawing curve of frozen fish. But the major cause of the inaccuracy of the modeling is on the assumption that the melting point of the frozen is constant.

Dissertação de mestrado integrado em Engenharia Biológica (área de especialização em Tecnologia Química e Alimentar)
The increase of fish consumption due to its nutritional characteristics, led to a stimulation of fishing industry, as regards the improvement of the processes for its conservation. Freezing and glazing are techniques commonly used in reducing the incidence of fish deterioration processes. In order to find an alternative to complement freezing and replace water glaze, the present work aimed at evaluating the effect of edible coatings of 0.5% and 1.5% chitosan on the quality of frozen fish. Both coatings - water glazing and chitosan coatings - were applied directly on Atlantic salmon (Salmo salar) frozen and stored for 6 months at -22 °C. Comparing both coatings with each other and with control uncoated samples, several parameters such as coating/glazing loss, weight loss, drip loss, TVC, TBA, TVB-N, K-value, pH and color coordinates L*a*b* were periodically evaluated. Favorable results were found for salmon samples coated with 0.5% chitosan in the control of coating loss and for the samples coated with 1.5% chitosan in maintaining the color of the salmon and controlling microbial contamination of samples frozen and thawed. In this work several parameters, such as coating loss, weight loss, drip loss, TVC, TBA, TVB-N, and K-value maintained quite stable due to the protection provided by a correct freezing temperature and a suitable control of its maintenance.
O aumento do consumo de peixe, devido às suas características nutricionais, obrigou a uma dinamização da indústria do pescado, no que respeita ao melhoramento dos processos de conservação do mesmo. A congelação e a vidragem são técnicas comumente usadas na redução da incidência dos processos de deterioração no pescado. Com o objetivo de encontrar uma alternativa que complementasse a congelação e substituísse o vidrado de água, o presente trabalho visou avaliar o efeito da aplicação de revestimentos edíveis de 0.5% e 1.5% de quitosano na qualidade do pescado congelado. Ambos os revestimentos – o vidrado de água e os revestimentos de quitosano – foram aplicados diretamente em salmão do Atlântico (Salmo salar) congelado e armazenado durante 6 meses a -22 °C. Comparando ambos os revestimentos entre si e com amostras controlo não revestidas, diversos parâmetros como perda de revestimento/vidrado, perda de peso, perda por gotejamento, TVC, TBA, TVB-N, K-value, pH e coordenadas de cor L*a*b* foram periodicamente avaliados. Encontraram-se resultados favoráveis para as amostras de salmão revestidas com 0.5% de quitosano no controlo da perda de revestimento e para as amostras revestidas com 1.5% de quitosano na manutenção da cor do salmão e no controlo da contaminação microbiana de amostras congeladas e descongeladas. Neste trabalho vários parâmetros, como a perda de revestimento/vidrado, perda de peso, perda por gotejamento, TVC, TBA, TVB-N e K-value, revelaram-se bastante estáveis devido à proteção providenciada por uma correta temperatura de armazenamento e por um controlo apropriado da sua manutenção.

碩士
國立海洋大學
食品科學系
90
Abstract The first part of this research was to study the nature of frozen denature of import Alaska Pollack surimi (75%W.C.) used for this study, as well as the changes of actomyosin (AM) in different stages of fish-gel preparation by combined uses of salt-soluble protein extractability, SH group analysis, DSC, and TSRM. It was found that only 66% of salt-soluble protein could be recovered by extraction, reflecting high frozen induced AM aggregation had occurred. Disappearance of SH group in surimi indicated that strong oxidative denaturation had occurred at M-head. That extremely large endothermic peak of M-tail being of the none frozen denature portion AM. The gel strength improvement achieved from the TGase induced inter-M-tail transamination crosslinking formed during holding treatments. The second part of this research was to study the changes of fish-gel quality as effect by water, potato starch, and sucrose additions to surimi. Preliminary study proved that the same optimized holding condition could be preserved while surimi being added with additives being held at 25℃ for 0hr, 4.5hr, and 8hr to arrow none, partial, and high amount of TGase induced crosslinking to be formed. Comparison to three kinds of commercial products; Chinese fish-ball, regular kamaboko, and high-grade kamaboko, the fish-gel prepared by using above holding conditions should superior elasticity over the commercial Chinese fish-ball. Among then, fish-gel resulted from 0hr holding posses a texture of slightly weaker hardness and elasticity than commercial regular kamaboko; where as fish-gel resulted from holding for 4.5hr (water 25%~80%, starch 5%~10%) and 8hr (water 40%~100%, starch 5%~10%) could reach for even excess the quality of commercial regular-grade and high-grade kamaboko.

碩士
國立高雄海洋科技大學
水產食品科學研究所
103
Seafood tends to perish quickly and has a shorter shelf life than other meat products. Low temperature (-20°C) frozen is the most commonly used method to preserve seafood. However, ice crystals are easily formed during frozen and deteriorate the sensory characteristics. Thus, a simple method adding salt into water to reduce the freezing temperature and formation of ice crystals was invented. In this research, fish was placed into a plastic bag containing the 1% or 3% salt water, and then stored at -20°C for 30 days. Two fish species, a farmed raised threadfin (Eleutheronema rhadinum) and wild caught Japanese butterfish (Psenopsis anomala) were tested. Fish samples were examined at every 5 days for mesophilic counts, psychrophilic counts, total volatile basic nitrogen (TVBN), pH, water content, water-holding capacity (WHC), and sensory characteristics before and after cooking. The fish samples in water without salt. Refrigerated at 4oC were used as controls. Although the samples in salty or regular water had the similar microbial counts, TVBN, and pH values, fish samples in salty water had significantly better sensory qualities (p<0.05) and longer shelf life than the frozen and refrigerated control samples. The fish samples in salty water also had higher water-holding capacity than the control samples. These results indicated that the salty water frozen could maintain higher water holing capacity and subsequently improve the sensory characteristics. In addition, our study showed the salty water frozen was a simple, low cost, and efficient method to preserve fish quality.

碩士
國立臺灣海洋大學
食品科學系
92
The purpose of this research was to survey quality stability of imported frozen threadfin bream surimi, and studies on optimization of setting treatment conditions and mechanism of salt-soluble protein changes in the fish-gel preparation as well as the additives, moisture and potato starch, affection on surimi gel properties. On stable qualities difference is great were found in surveying on the most SA grade surimi. The low grade surimi was evidence most possibility to be the partial denature due to the improper processing on store. Monitor the major salt-soluble protein, AM changes during setting by DSC and TSRM, it was evidence the AM in free A and M forms was converted to an AM complex and a TGase promote cross link type AM complex to benefit the final fish gel strength during setting. It was found the performing of a 5 oC/20 h setting treatment could improve the gel strength from 644 ±15 g-cm to 791 ±8 g-cm ; 25 oC/6 h setting could result an even phenomenal improve on the product gel strength up to 2200 ±32 g-cm, respectively. To evaluate the changes of gel product qualities as effected by additives, with comparable to commercial fish ball and kamaboko, for gels prepared without setting treatment additives, kamaboko type product were resulted at a lower moisture content 78 %, resemble kamaboko type product were resulted at 80 % wc, fish ball type product were resulted at a higher moisture content 84 %. For gels prepared with a 25 oC/6 h setting treatment prior to cooking, gel properties tougher then high grade kamaboko was resulted for gels contenting any moisture content between 76-83 %, gels possessing exactly similar properties to high grade kamaboko could only be result at high moisture content between 80-84 %. Addition of potato starch could only increase the breaking force and could not significantly affected the deformation at break, higher then 7.5 % level of starch addition would result gel with unfavorable sandy texture.

Dissertação de mestrado integrado em Engenharia Biológica (área de especialização em Tecnologia Química e Alimentar)
Fish consumption has gradually increased in recent years, mainly due to its unique nutritional characteristics and their benefits to the health of consumers. Glazing is a technique used in addition to freezing and is intended to retard the deterioration of fish. This work focuses in the study of the variables (fish temperature, coating temperature, dipping time) that affect the thickness of an edible coating (water glaze and 1.5% chitosan) applied on frozen fish. Samples of frozen Atlantic salmon (Salmo salar) at -15, -20, -25 °C were glazed with water at 0.5, 1.5, 2.5 °C and coated with chitosan at 2.5, 5, 8 °C during 10 to 60 seconds. For both water and chitosan lowering the salmon and coating temperature results in an increase of the thickness. The thickness of the coatings used was always higher for chitosan than for water, reaching a maximum thickness of (1.41±0.05) mm for chitosan and (0.84±0.03) mm in water. By DSC analysis it was found that both freezing temperature and cystallization heat are lower in 1.5% chitosan solution than in water, which favors the phase change. Salmon temperature profiles allowed confirming, for different dipping conditions, if the salmon temperature is within the limits of food safety for the growth of microorganisms pathogens. The maximum time salmon may be dipped in the coating (safe dipping time) for the tested conditions never exceeds 40 seconds. The average temperature of the coating that adhered to the salmon was determined experimentally, being important for future attempts to predict the coating thickness.
O consumo de peixe tem aumentado progressivamente nos últimos anos, devido sobretudo às suas características nutricionais únicas e aos seus beneficios para a saúde dos consumidores. A vidragem é uma técnica usado como suplemento à congelação e a sua finalidade é retardar a deterioração do pescado. Este trabalho foca-se no estudo das variáveis (temperatura do peixe, temperatura do revestimento, tempo de mergulho) que afectam a espessura de um revestimento edivel (água e quitosano 1.5%) aplicado em peixe congelado. Amostras de salmão do Atlântico congelado (Salmo salar) a -15, -20, -25 °C foram vidradas com água a 0.5, 1.5, 2.5 °C e revestidas com quitosano a 2.5, 5, 8 °C durante 10 a 60 segundos. Tanto na água como no quitosano a descida da temperatura do salmão e do revestimento resulta num aumento da espessura. A espessura obtida nos revestimentos usados foi sempre superior no quitosano, atingindo uma espessura máxima de (1.41±0.05) mm para o quitosano e (0.84±0.03) mm na água. A análise DSC permitiu constatar que tanto a temperatura de congelação como o calor de cristalização são inferiores na solução de 1.5% quitosano em comparação com a água, o que favorece a mudança de fase. Os perfis de temperatura do salmão permitiram confirmar, para diferentes condições de mergulho, se a temperatura do salmão se encontra dentro dos limites de segurança alimentar, de modo a evitar o crescimento de microorganismos patogénicos. O tempo máximo que o salmão pode estar mergulhado no revestimento (tempo de mergulho seguro) para as várias condições testadas nunca ultrapassa os 40 segundos. A temperatura média do revestimento que aderiu ao salmão foi determinada experimentalmente, sendo importante para tentativas futuras de previsão da espessura de revestimento.

碩士
國立海洋大學
食品科學系
89
In order to investigate the optimum conditions for the recovery of native proteins from freeze-denatured fish muscle using NADPH-sulfite reductase, Escherichia coli CCRC 11634 was cultivated in a medium composed of 4.0 % sucrose, 0.4 % yeast extract and 0.4 % tryptone at pH 7.5 with shaking (100 rpm) at 37 ºC for 18 h, then harvested and sonicated. The crude enzyme was subjected to ammonium sulfate fractionation. Precipitate at 30 ~ 60 % saturation of ammonium sulfate was collected. The NADPH-sulfite reductase was purified to electrophoretic homogeneity by DEAE Sephacel and Sephacryl S-300 HR chromatographs. The recovery of total NADPH-sulfite reductase activity was 31.7 %, while the molecular weights was 119,000 estimated by Sephacryl S-300 HR gel filtration. The optimal pH and temperature for the enzyme activity were 7.7 and 25 ºC, respectively. It was inhibited by IAA, PMSF, NEM, PCMB, KCN, Hg2+, Fe2+, Fe3+, Ca2+, Co2+, Cu2+, Cd2+, Zn2+, Mn2+ and Ba2+. The reactive SH increased from 4.20 x 10-5 to 7.65 x 10-5 mol / g mince, while the gel strength increased from 109.4 to 211.2 g x cm when 0.03 unit / g surimi was added. SDS-PAGE suggested the high recovery of native actomyosin after the reaction with NADPH-sulfite reductase.

Pacific whiting (Merluccius productus) is the most abundant groundfish species off the California, Oregon and Washington Coasts. The fish are mainly used as a raw material for the production of surimi. However, it is not economically wise to depend only on one product. There is a need to diversify the industry and develop a portfolio of product forms able to compete on the global marketplace. This study examines the characteristics of Pacific whiting individually quick frozen (IQF) fillets through an evaluation of consumer acceptability and sensory analysis, as well as their correlations to biochemical and physical properties. Additionally, a comparison is made between Pacific whiting IQF fillets and characteristics from seven other fish species. Sensory analysis by a trained panel showed Pacific whiting scoring highest in the flavor category of shellfish, medium in overall flavor intensity and fresh fish flavor, and high in moistness. Two different cooking methods: microwave (rapid) and conventional oven (slow) were studied with the results showing that the rapid method improved a number of texture attributes. Correlations between sensory texture attributes and instrumental texture results of Pacific whiting and the protease activity were found for both cooking methods but much higher in the slow one. All eight species were tested in a consumer test using a nine-point Hedonic scale. There were no significance differences (p>0.05) in flavor, texture, and overall acceptance of Pacific whiting with most of other commercial fish. However, the amount of variation in each group was high. No significant differences were found in firmness of Pacific whiting when compared to Dover sole. Five-point purchase intent scale showed no differences in consumers' willingness-to-buy when compared to species presently available in the marketplace. Pacific whiting IQF fillets, kept in frozen storage for 12 months, showed no differences in the flavor and texture attributes with fillets frozen for one month. The following findings are based on the information gained from the focus group: (1) The most important factor affecting consumers' purchasing decision on fish is flavor, (2) Fish flavor must be fresh, mild, pleasant, and true to species, and (3) Fish texture is varied. Texture is not as important as such factors as flavor, odor, appearance, and thickness of fillets. Pacific whiting was found to be tasty and acceptable to the focus group participants. Qualitative and quantitative data collected from the focus group and the consumer tests, combined with its sensory characteristics' similarity to desirable commercial fish suggest a good potential of Pacific whiting in being utilized as IQF fillets.
Graduation date: 1997

Consumers demand for high quality food stuffs with no preservatives and with extended shelf-life, retaining the quality properties, led to the development of new processing technologies. One of those technologies, studied in this work, is High Pressure Processing (HPP), which has shown good results on fish shelf-life extension, with great importance in fish safety by inactivation of microbial load (mostly pathogenic microorganisms) in refrigerated fish, and inactivation of certain degradative enzymes, mainly in frozen fish. Fish products are usually stored under refrigeration or frozen to maintain their quality and safety patterns. However, there are still several reactions that cause fish degradation. For instance, even under frozen storage, enzymatic activity still occurs. According to the literature, HPP has shown to be a promising pre-treatment to inhibit these enzymes and extend frozen fish-shelf-life. This work aimed to determine the effect of HPP (150 MPa for 2 minutes) and storage temperature (-10, -20 and -30 ºC) on the quality of frozen hake muscle (Merluccius merluccius). It was verified that HPP resulted in a decrease of calpains activity (59 %) after 12 months of storage at -20 ºC and maintained the activity of acid phosphatase, cathepsin B and calpains after 12 months at -30 ºC Furthermore, the quantification of sulfhydryl (SH) groups indicated that the HP treatment results in higher SH content (increase up to 190%), as well as increased storage time (increase up to 120%), being this increase probably related with protein denaturation of fish muscle. This work presents relevant information concerning the employment of HP pre-treatments to reduce enzymatic activity associated to quality loss in frozen European hake (Merluccius merluccius). This type of processing can so be of interest to enhance the quality preservation of frozen hake, as well as of other species.
A exigência dos consumidores por produtos alimentares de elevada qualidade sem conservantes e com tempo de prateleira alargado, mantendo a sua qualidade, levou ao desenvolvimento de novas tecnologias para o seu processamento. Uma dessas tecnologias, abordada neste trabalho, é o Processamento por Alta Pressão (HPP), que tem apresentado bons resultados na extensão do tempo de prateleira em peixe, com especial importância para a segurança dos produtos, ao reduzir a carga microbiana (maioritariamente patogénicos) em peixe refrigerado e inibir a atividade de certas enzimas degradativas, principalmente em peixe congelado. Os produtos da pesca são normalmente armazenados em refrigeração ou congelados, de modo a manter os seus padrões de qualidade e segurança. No entanto, há diversas reações que ainda assim causam a degradação do peixe. Por exemplo, mesmo enquanto congelado, o peixe sofre alterações devido à atividade enzimática. De acordo com a literatura, o HPP mostrou grande potencial na inativação dessas enzimas e, consequentemente, na extensão do tempo de prateleira do peixe. Este trabalho visou determinar o efeito de um pré-tratamento por alta pressão (150 MPa por 2 minutos) e temperatura de armazenamento (-10, -20 e -30 ºC) na atividade enzimática do músculo de pescada congelada (Merluccius merluccius). Verificou–se que o pré-tratamento de HP possibilitou a diminuição de atividade das calpaínas (59 %) após 12 meses a -20 ºC e a manutenção das atividades da fosfatase ácida, catepsina B e calpaínas após 12 meses a -30 ºC. Verificou-se ainda um aumento no conteúdo em grupos tiol (SH) com o pré-tratamento (até 190%) e ao longo do tempo de armazenamento (até 120%), estando esse aumento possivelmente relacionado com a desnaturação proteica do músculo de peixe. Este trabalho apresenta assim informação importante relativa à aplicação de pré-tratamentos por alta pressão para reduzir a atividade enzimática associada a deterioração da pescada congelada (Merluccius merluccius). Este tipo de processamento pode assim ser relevante para uma melhor preservação da qualidade da pescada congelada, bem como possivelmente de outras espécies
Mestrado em Biotecnologia

PhD Thesis in Chemical and Biological Engineering
Even though this fact might not be fully realized by the business owners and consumers, the wide use of water glazing in frozen fish industry (as a layer of ice over the frozen fish products) works just like an edible coating that protects the product during storage. Glazing aims at acting as a physical barrier to cold storage deterioration especially when the product is subjected to inadequate cold storage. Nevertheless, in addition to having a high procedural cost due to the necessary equipment, glazing has long been shrouded in controversy over the amount of water applied to the product. In extreme cases, up to 40 % glaze can be observed for some seafood products, seeking clearly more than just guaranteeing product quality. A paradigm change would be the use of alternatives to simple water that could improve the protection during storage and add functionalities to the protective coating. On top of that, the industry should be able to define the optimum amount of protective coating necessary to fulfill its original purpose. With this purpose the work was divided in five steps. Firstly it was necessary to identify the ability of a chitosan solution used directly on frozen salmon (in similar conditions as the ones used in the industry to glaze frozen fish) to achieve better results than simple water when, after thawing, samples were tested for freshness parameters (TVC, TVB-N, K-value, pH, TBA). At this first stage it was studied how different chitosan concentrations and coatings uptake could affect these parameters. Samples were stored at -5 ⁰C with the purpose of accelerating any negative effect promoted by cold storage conditions. Then, in a second step, the chitosan concentration that better performed on step 1 together with a three-times higher concentration (since none of the used in step 1 showed clear antimicrobial activity) were used and samples were stored during a sixmonths period at -22 ⁰C. The parameters to assess the deterioration were basically the same of the first step, but colour changes were also measured since this is, particularly in salmon, a very important factor in the quality perceived by consumers. After identifying that chitosan coatings perform better in coating loss, colour change and demonstrate antimicrobial activity, in step 3 it was meant to study the effect that the coating application conditions have on its thickness. With this step it was possible not only to identify what could be the thickness of the coating corresponding to the samples that performed better in step 2 but also to predict which conditions to use when a defined thickness is desired. This step validated that the same thickness of water glazing can be obtained by chitosan coatings with energy savings (salmon and coating temperature can be higher). The heat transfer phenomenon that is in the origin of the coating formation was also studied and salmon temperature profiles during dipping time were presented and analyzed. The introduction of the concept of Safe Dipping Time (SDT) was proposed, challenging the industry to reflect on the possible effects of temperature rise in frozen fish during dipping. Realizing that in the “real world” storage conditions are not always perfect and (especially during transport/retail) frozen products can face temperature fluctuations, the ability of chitosan coating to outperform water glazing under those conditions was evaluated (step 4). Product was stored during 70 days in a freezing chamber continuously fluctuating between -15 ⁰C and -5 ⁰C and freshness parameters (pH, Total Volatile Basic Nitrogen (TVB-N), Total Viable Count (TVC)), as well as coating loss and colour parameters were evaluated. Finally, step 5 was meant to verify if the use of chitosan coatings would be noticeable by consumers due to alterations of the salmon’s organoleptic characteristics, when stored at -18 ⁰C during a period of six months. A trained panel was used to evaluate chitosan coatings and water glazing against control samples after two, four and six months of storage. Overall, chitosan demonstrated to be an alternative to the use of simple water for the coating/glazing of frozen fish since: a) it presented a slower rate of coating loss, b) it reduced the microbial contamination of the product, c) it preserved the colour of the product and, d) at the moment of consumption, no differences were perceived by consumers between samples treated with water and chitosan solution.
Mesmo que esse facto possa não ser reconhecido pelos empresários e consumidores, a ampla utilização da vidragem na indústria de pescado congelado (como uma camada de gelo que envolve o pescado congelado) funciona como um revestimento edível que protege o produto durante o armazenamento. A vidragem visa atuar como uma barreira física para proteção da qualidade do pescado congelado durante o armazenamento a frio, especialmente quando o produto é submetido a temperaturas inadequadas. No entanto, além de ter um custo elevado, devido ao processo e equipamento necessário, o uso de vidragem tem sido envolvido em controvérsia devido à quantidade de água aplicada. Em casos extremos, é observado que esta pode representar 40% do peso do produto final, procurando vantagens para além de melhorias na qualidade do produto. Para mudar este paradigma seria necessário procurar alternativas para o revestimento de água que permitissem melhorar a proteção e adicionar funcionalidades ao revestimento. Para além disso, a indústria deveria ser capaz de definir a quantidade de revestimento necessária para cumprir o seu propósito original. Para este efeito, o trabalho foi dividido em cinco etapas. Primeiro foi necessário identificar a capacidade de uma solução de quitosano, aplicada diretamente no salmão congelado (em condições similares às utilizadas na indústria), em alcançar melhores resultados do que a água, quando, após descongelação, são avaliados parâmetros de frescura (TVC, ABVT, valor-K, pH, TBA) e do desempenho do revestimento. Nesta primeira fase, foi estudado como diferentes concentrações de quitosano e quantidade de revestimento aplicado podem afetar os resultados. As amostras foram armazenadas a -5 ⁰C para acelerar efeitos negativos que possam surgir pela conservação em frio. Em seguida, numa segunda etapa, utilizou-se a concentração de quitosano que registou melhor desempenho na etapa 1 e outra 3 vezes mais elevada (uma vez que nenhuma das utilizadas na etapa 1 mostrou uma clara actividade antimicrobiana) durante 6 meses e em condições de temperatura de conservação semelhantes às utilizadas na indústria (-22 ⁰C). Os parâmetros de avaliação da deterioração foram basicamente os mesmos da primeira etapa, mas foi também avaliada a mudança de cor uma vez que, particularmente no salmão, é um factor muito importante para a qualidade percebida pelos consumidores. Depois de identificar que os revestimentos de quitosano tiveram um melhor desempenho na perda de revestimento, na alteração de cor e que demonstram atividade antimicrobiana, na etapa 3 foi estudado o efeito que as condições de aplicação de revestimento têm na espessura de revestimento. Com este passo foi possível não só identificar qual poderia ser a espessura de revestimento correspondente às amostras com melhor desempenho na etapa 2, mas também, prever as condições a usar para obter uma determinada espessura. Este passo validou que a mesma espessura de vidragem poderá ser obtida por revestimentos de quitosano com poupança de energia (utilizando temperatura de salmão e de revestimento mais elevadas). O fenómeno de transferência de calor que está na origem da formação de revestimento foi também estudado e definidos os perfis de temperatura no interior do salmão durante o tempo de imersão. A introdução do conceito de Tempo Seguro de Imersão foi proposta com o objetivo de desafiar a indústria a refletir sobre o efeito do aumento de temperatura no peixe congelado enquanto este está imerso para aplicação da vidragem. Reconhecendo que no mundo real nem sempre as condições de conservação dos produtos congelados são as ideais e que (em particular durante o transporte e distribuição) o produto sofre oscilações de temperaturas, foi avaliado se a vidragem com quitosano teria um melhor desempenho que a água simples nessas condições (etapa 4). O produto foi armazenado durante 70 dias numa arca congeladora que oscilava continuamente entre -15 ⁰C e -5 ⁰C procedendo-se à avaliação da perda de cor e vidragem bem como dos parâmetros TVC, ABVT e pH. Finalmente, na etapa 5, verificou-se se o uso de revestimentos de quitosano seria percetível pelo consumidor devido a alterações nas características organolépticas do salmão, quando armazenado à temperatura de -18 ⁰C durante um período de seis meses. Um painel treinado foi usado para avaliar revestimentos de quitosano e a de água simples quando comparados com amostras controlo, após dois, quatro e seis meses. Em geral, o quitosano demonstrou ser uma alternativa ao uso de água no revestimento de peixe congelado, uma vez que: a) apresenta uma menor taxa de perda de revestimentos, b) reduz a contaminação microbiana do produto, c) preserva a cor do produto e d) no momento do consumo, não é percebido de forma diferente pelos consumidores.

This project provides a thorough investigation on new consumption habits, Cod Fish consumption and the Added-Value Frozen Fish market. The goal of this work project is, thus, over a deep understanding of AVFF market, provide Riberalves with a comprehensive recommendation on how to innovate its existing Cod Fish offer through an entry on the AVFF market with Cod Fish based products.. The outcomes of this project are three product proposals together with a packaging prototype and a pricing and discount strategy to allow the entrance of the company in this new market by taking advantage of company’s strengths

The consumption of seafood in the United States has increased rapidly in recent years due to high quality protein and health benefits of seafood. Seafood can be a carrier for bacteria normally distributed in the marine environment and, in some cases, can be contaminated by human pathogens. Therefore, there is a potential health risk if seafood is consumed raw or undercooked. However, information regarding prevalence of foodborne pathogens in retail seafood products and the ability of pathogens to survive in the products during refrigerated and frozen storage is limited. The objective of this study was to generate such information for a better understanding of distribution of foodborne pathogens in seafood products and provide data which might be used for risk assessment of foodborne infection associated with seafood consumption. A total of 45 seafood products were collected from local retail stores and analyzed for aerobic plate counts (APC) and psychrotrophic bacterial counts (PBC) as well as presence of foodborne pathogens, including Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, Staphylococcus aureus, Vibrio parahaemolyticus, and Vibrio vulnificus according to procedures described in the U.S. Food and Drug and Administration Bacteriological Analytical Manual (BAM). Presumptive isolates for each foodborne pathogen were further characterized by biochemical reactions using commercial identification kits and confirmed with polymerase chain reaction (PCR) assay. The samples had bacterial populations ranging from 1.90 to 6.11 CFU/g for APC and from 2.00 to 6.78 CFU/g for PBC. According to the microbiological criteria of International Commission on Microbiological Specifications for Foods (ICMSF), all 45 samples were considered acceptable quality (APC < 10⁷ CFU/g, E. coli < 3 MPN/g) with most samples (93.3%) being good quality (APC < 5 × 10⁵ CFU/g, E. coli < 3 MPN/g). No E. coli O157:H7, Salmonella, S. aureus, V. parahaemolyticus, and V. vulnificus was detected in any samples. Two previously frozen shrimp products (4.4%) were confirmed to carry L. monocytogenes. Studies of growth and survival of L. monocytogenes (3 strains), S. aureus (2 strains), and Salmonella (2 serovars) in raw yellowfin tuna meat stored at 5 - 7 °C for 14 days revealed that L. monocytogenes had the ability to multiply in the tuna meat during refrigerated storage while populations of S. aureus and Salmonella were reduced by 1 to 2 log CFU/g after 14 days at 5 - 7 °C. Studies of holding raw yellowfin tuna meat contaminated with L. monocytogenes, S. aureus, and Salmonella at -18 ± 2 °C for 12 weeks observed that all three pathogens, except Salmonella Newport, in tuna samples survived the frozen storage with less than 2- log of reductions in the populations over 12 weeks of storage. No viable cell of Salmonella Newport was detected in samples after 42 days storage at -18 °C. Raw seafood can be a carrier of foodborne pathogens, particularly L. monocytogenes, and many foodborne pathogens can survive in frozen products for several months. Consumption of raw or undercooked seafood products may lead to human infection if the products are contaminated with pathogens. Therefore, sanitation standard operating procedure (SSOP), good manufacturing practice (GMP) and hazards analysis and critical control points (HACCPs) programs shall all be implemented in the seafood industry to prevent seafood products from being contaminated with foodborne pathogens during handling and processing. Moreover, proper storage of raw seafood products and avoiding cross-contamination during handling at the retail levels also helps to minimize risk of human infection associated with ready-to-eat products.
Graduation date: 2013

碩士
國立臺灣海洋大學
水產養殖學系
105
Two experiments were conducted to evaluate the effects of partial replacement of fish meal protein by dry maggot meal (DMM) and frozen maggot (FM) on the growth performances and moulting frequency of white shrimp, Litopenaeus vannamei. In experiment 1-1, the dietary fish meal protein was replaced by 0, 20, 40, 60 and 80% dry maggot meal. Five isonitrogenous (32%), isolipid (12%) and isocaloric (316 Kcal/100g) diets were fed 0.059±0.004g white shrimps for eight weeks. The weight gain ranged from 2829 to 3796%. The weight gain of shrimp fed with 60% fishmeal protein replaced by DMM was significantly higher than that of shrimp fed with 0 to 40% fishmeal protein replaced by DMM. The weight gain of shrimp fed with 80% fishmeal protein replaced by DMM was significantly higher than that of shrimp fed control diet. The survival of white shrimps ranged from 80 to 90%. In experiment 1-2, the same experiment diets were used to monitor molting frequency of shrimp. Moulting frequency increased with the increasing dietary DMM. The survival of white shrimps were 100%. In experiment 2-1, the dietary fish meal protein was replaced by 0, 15, 30, 45 and 60% frozen maggot. Five isonitrogenous (32%), isolipid (12%) and isocaloric (316 Kcal/100g) diets were fed 0.011±0.000g white shrimps for six weeks. The weight gain ranged from 5073 to 7070%. The weight gain of shrimp fed with 45% fishmeal protein replaced by FM was significantly higher than that of shrimp fed control diet. The weight gain of shrimp fed with 60% fishmeal protein replaced by FM was significantly higher than that of shrimp fed control diet. The survival of white shrimp ranged from 86 to 97%. In experiment 2-2, the same experiment diets were used to monitor molting frequency of shrimp. Moulting frequency increased with the increasing FM. The survival of white shrimps were 100%.

O presente trabalho descreve as atividades desenvolvidas no decorrer do estágio curricular, no âmbito do Mestrado em Engenharia Alimentar realizado na empresa Mar Cabo – Produtos Congelados, Lda., que tem como “core business” a preparação de pescado congelado. A atividade principal do estágio baseou-se na melhoria do sistema de gestão integrado da empresa, com o intuito de certificar a mesma no referencial International Featured Standard (IFS) Food 6.1, uma das normas internacionais com maior destaque na área alimentar. Todo o referencial foi analisado com o intuito de compreender os melhores métodos para o cumprimento dos requisitos, assim como a legislação aplicável ao setor alimentar e dar resposta ao objetivo traçado. Foi então necessário realizar uma auditoria de diagnóstico que teve como propósito a avaliação do ponto de situação da empresa face ao cumprimento dos pré-requisitos necessários para a obtenção de certificação. Esta auditoria teve como ferramenta a checklist IFS Food 6.1. O passo seguinte foi a elaboração de toda a documentação associada, em falta, ou melhoria de documentação já existente. Neste ponto foi onde se prendeu grande parte do trabalho desenvolvido na empresa em questão. Foram desenvolvidas distintas tipologias de documentação, de entre as quais se destacam: procedimentos operacionais, instruções de trabalho, registos, planos de auditorias e fluxogramas. Foram ainda realizadas formações para novos colaboradores em higiene e segurança alimentar, gestão de alergénios e food defense. O processo de certificação mostrou-se bastante complexo e moroso, acarretando um grande investimento em recursos humanos, infraestruturas e equipamentos. Todo o investimento tornou-se visível aquando da auditoria de certificação da empresa, na qual pude participar enquanto membro da equipa de segurança e qualidade.
The present report describes the activities developed during the internship at the company Mar Cabo, Lda., whose core business is the preparation of frozen fish. This was performed in the scope of the Master’s in Food Engineering. The main activity of the internship was based on the improvement of the integrated management system of the company with the purpose of obtaining the certification in the reference International Featured Standard (IFS) Food 6.1, one of the most important and recognised international certifications in the food area. The entire standard was analysed in order to understand the best methods to meet the requirements, as well as the legislation applicable to the food sector and to respond to the objective set. It was then necessary to carry out a diagnostic audit aimed at assessing the company’s status regarding compliance with the necessary prerequisites for obtaining certification. This audit had the IFS Food 6.1 checklist as a tool. The next step was to elaborate any missing associated documents, or to improve existing documents. The most of the work developed at the company was held on this topic. Different types of documents were developed, among which the following stand out: operational procedures, work instructions, records, audit plans and flowcharts. Training was also provided for new employees in food hygiene and safety and food defense. The certification process proved to be quite complex and slow, resulting in a large investment in human resources, infrastructure and equipment. All investment became visible during the company’s certification audit, in which I was able to participate as a member of the safety and quality team.