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.

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

Made available in DSpace on 2015-10-06T13:03:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-08-29. Added 1 bitstream(s) on 2015-10-06T13:19:05Z : No. of bitstreams: 1 000850093.pdf: 2140143 bytes, checksum: 727f5e87edf6a9978bbd8ad8c267e57b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A tilápia, além de possuir vantagens produtivas, origina produtos com grande aceitação pelo mercado. Em sua nutrição, podem ser utilizados aditivos com fins zootécnicos, pigmentantes ou antioxidantes. Este estudo avaliou o efeito da suplementação da dieta para tilápias com biomassa de Rubrivivax gelatinosus sobre o desempenho zootécnico e parâmetros hematológicos e histológicos dos animais, e sobre as características de qualidade dos filés. O experimento contou com seis tratamentos, compostos de um grupo controle, um grupo com pigmentante comercial e quatro grupos com a biomassa nas concentrações de 175, 350, 700 e 1400 mg/kg. Peixes pesando 21,42 ± 5,65g foram criados por 74 dias em sistema com recirculação de água e abatidos nos dias 0, 18, 43, 58 e 74. Não foram encontradas diferenças para os resultados das análises de desempenho, histológicas e hematológicas. Os filés dos grupos alimentados com os aditivos apresentaram menor umidade que o controle (p < 0,05) e os filés dos grupos alimentados com biomassa apresentaram maiores teores protéicos (p < 0,05). Não houve diferenças entre os tratamentos para os valores de pH, lipídeos e cinzas. Quanto à cor dos filés, todos os tratamentos com aditivos aumentaram a intensidade de vermelho (p < 0,05). Em todos os tratamentos, a rancidez dos filés foi crescente durante o armazenamento, embora em menores valores nos filés dos grupos tratados com as maiores concentrações de biomassa (p < 0,05). A biomassa de R. gelatinosus não promoveu alterações no desempenho nem nos parâmetros hematológicos e histológicos, e mostrou-se capaz de melhorar os aspectos de qualidade e conservação dos filés. Dessa forma, confirma-se a viabilidade do uso desse aditivo na alimentação de tilápias para incrementar a preservação da carne congelada / More than having productivity advantages, tilapia fish yields products with great market acceptance. For its nutrition, additives aiming at increasing zootechnical, pigmenting or antioxidant features may be used. This study evaluated the effect of the supplementation of tilapia diets with Rubrivivax gelatinosus biomass on the performance and hematological and histological parameters of the animals, and on the quality of the fillets. The experiment comprised six treatments, made of a control group, a group containing commercial pigment and four groups with biomass concentrations of 175, 350, 700 and 1400 mg/kg. Fishes weighing 21.42 ± 5.65 g were reared for 74 days in a system with water recirculation and slaughtered at days 0, 18, 43 and 74. No difference was detected for performance, histological and hematological analyzes among treatments. Fillets of the groups fed additives had lower moisture than the control (p < 0.05) while the fillets of the groups fed the biomass had the highest protein percentages (p < 0.05). No differences were detected among treatments for pH, lipids and ash values. Regarding to the color of the fillets, all treatments with additives increased redness at the measured sites (p < 0.05). For all treatments, rancidity in the fillets increased during storage, although the groups treated with the highest biomass concentrations had the lowest values (p < 0.05). R. gelatinosus biomass did not change performance or hematological and histological parameters, and proved to be capable of improving fillets quality features and conservation. Thus, it was shown the viability of the use of this additive in tilapia feed to increase the preservation of frozen meat / FAPESP: 2011/01103-2

The present work examines the antimicrobial efficacy of the essential oils of thyme, oregano and carvacrol against L. monocytogenes biofilms produced on stainless steel coupons and for control of L. monocytogenes growth on raw catfish fillets stored at 4°C for 10 days. At 0.5%, all three essential oils were highly effective in completely eliminating L. monocytogenes cells from stainless coupons within 24 h as compared to the untreated control yielding ~7 log CFU/cm2 L. monocytogenes. When catfish inoculated with L. monocytogenes were dipped for 30 min at 4°C in essential oil solutions of thyme and oregano at 1%, 2% and 5%, there were no significant reductions in L. monocytogenes counts on the fresh catfish fillets as compared to untreated control. For the same conditions, treatment with 2% carvacrol resulted in a complete reduction of 4 log CFU/g of L. monocytogenes counts from fresh catfish fillets.

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Edam and Cheddar whey were thermized (T) for different time periods (5–30 min) at 70 degrees Celsius, vacuum evaporated, and spray dried to obtain whey powders (WP). Native and thermized WP were evaluated for antioxidative properties. Edam and Cheddar WP significantly reduced thiobarbituric acid-reactive substances (TBARS) and peroxide value (PV) in ferric-catalyzed soybean oil emulsions. Thermization significantly improved antioxidative properties of WP with 5T, 10T, and 15T treatments showing better protective effects compared to 20T and 30T treatments. Based on these results, native (0T) and thermized (5T, 10T, and 15T) Edam and Cheddar WP coatings, with and without enzymatically hydrolyzed casein (CH), were used to reduce oxidative degradation and moisture loss of cubed beef steak and pork loin. Thermized treatments significantly reduced TBARS and PV in both types of meat, with CH containing treatments showing enhanced antioxidative properties. Protein oxidation as reflected by carbonyl formation and a decrease in sulfhydryls was also reduced by thermization. Treated and native WP coatings significantly reduced moisture loss of meat samples. Cubed beef steak treated with Cheddar WP coatings were evaluated for microbiological quality and basic sensory attributes. Although not statistically significant, 5T, 10T, and 10TCH treatments numerically showed potential for microbial reduction up to 4 days of storage. Sensory evaluation showed significant protection of key sensory attributes by treatments throughout the storage period when compared to controls with the 5 min thermization showing the best effect on lowering offlavor development based on sensory scores. The effect of pH and glucomannan (GM) on antioxidative properties of thermized (5T) Cheddar WP coatings applied to catfish fillets was also investigated. Coatings at pH 7.0, 7.5, and 8.0 (with GM) showed markedly greater protection against oxidative degradation compared to coatings without GM, as reflected by TBARS values and PV after 7 days of storage. Carbonyl formation and oxidation of sulfhydryl groups were also significantly reduced by coatings containing GM. Cheddar WP-based edible coatings (pH 7.0–8.0) with GM markedly reduced lipid oxidation and protein oxidation of fresh catfish fillets.

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