published_or_final_version / Botany / Master / Master of Philosophy

This study determined the effects of sucrose and sorbitol as cryoprotectant (CR) on the quality and sensory attributes of bone-in hams (N=90) injected (20% of weight) with following brine treatments (BT): control (2% sucrose; CNT), 2% CR (1% sucrose, 1% sorbitol), 4% CR (2% sucrose, 2% sorbitol). Hams that were frozen and injected with CNT after thawing (FZ I) were used as a negative control. After reaching the designated ST all bone-in hams were thawed under refrigeration (4oC) and FZ I hams were then injected with CNT (n=8). Hams were cooked to 70oC, chilled (7oC), sliced, vacuum packaged and analyzed for lipid oxidation, color, protein solubility and purge at 0, 28, and 56 of refrigerated storage while sensory evaluation and shear force determinations were conducted at 28 d. Color, pH, and lipid oxidation values tended to remain similar or decrease as frozen storage time increased. Water holding capacity (percent bound water) and protein solubility increased as frozen storage increased. The 4% CR BT exhibited the lowest shear force value (4.04 N/g) but was not statistically different than CNT or FZ I on ham knuckle muscles. Trained sensory panelists found hammy and salty were the strongest flavor and basic taste attributes. The results of this study confirm that quality attributes and protein functionality were maintained but not significantly improved by injecting a brine solution with cryoprotectants prior to freezing.

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.

Master of Science / Department of Animal Sciences and Industry / Terry Houser / Two studies were conducted to determine the effectiveness of naturally smoked sugar in a conventional and natural curing brines to inhibit lipid oxidation in frozen, aerobically packaged, layout style bacon. Commercial pork bellies were trimmed and cut in half creating anterior and posterior sections. Each section was randomly assigned to one of two treatments targeted 12% injection: control brine or a brine containing naturally smoked sugar (n =15/treatment). In the first study a conventional control brine consisted of 76.4% water, 11.8% salt, 8.00% sugar, 1.70% sodium phosphate, 1.60% sodium nitrite, and 0.450% sodium erythorbate. The treatment brine contained the same ingredients with the addition of 5.00% naturally smoked sugar. In the second study a natural control curing brine was utilized and contained 72.0% water, 13.4% sea salt, 8.00% cane sugar, and 6.67% celery juice. While treatment brine had the same ingredients as the natural control brine with the addition 5.00% smoked sugar. Bacon slices were randomly assigned to four sensory and GCMS frozen storage periods (0, 40, 80, and 120 day) or seven thiobarbituric acid reactive substances (TBARS) frozen storage times (0, 20, 40, 60, 80, 100, and 120 day). To measure lipid oxidation trained sensory evaluation, TBARS, and gas chromatography mass spectrometry (GCMS) was conducted after the assigned frozen storage periods. All bacon slices were stored aerobically at -18 ± 2 °C for their designated storage period. The first study panelist scores for oxidized flavor of the conventional control bacon increased from day 0 to 120; whereas the naturally smoked sugar treatment had decreased panelist scores (P > 0.16) for oxidized flavor intensity compared to the control bacon. Also, TBARS results values for the conventional control bacon increased (P < 0.01) from day 20 to day 120; while the conventional naturally smoked sugar treatment remained constant (P > 0.99). Hexanal content for conventional control increased (P < 0.003) during frozen storage; but naturally smoked sugar TBARS values were not different from day 0 of storage (P > 0.734). Concentration of heptanal in conventional control bacon was the highest (P < 0.003) at day 80 and 120 of frozen storage. Heptanal content in conventional bacon with naturally smoked sugar was not different from day 0 of frozen storage (P > 0.846). Conventional bacon formulated with naturally smoked sugar had greater concentrations of creosol and syringol than control bacon (P < 0.003). In the second study, naturally cured bacon had increased panelist scores for oxidized flavor from day 0 to 120 of frozen storage (P < 0.001). Natural bacon with smoked sugar had oxidized flavor scores that remained constant during frozen storage (P > 0.936). Naturally cured bacon displayed increased TBARS values from day 20 to 120 of frozen storage (P < 0.001). Naturally cured bacon with smoked sugar exhibited static TBARS values throughout the frozen storage period (P > 0.196). Thus, smoked sugar is an effective antioxidant in frozen sliced, aerobically packaged, conventionally cured and naturally cured bacon.

A carne de frango, em razão da elevada concentração de ácidos graxos insaturados, é altamente suscetível ao processo de oxidação lipídica, que afeta sabor, aroma, cor e textura dos alimentos, limitando sua estabilidade e vida-útil. Devido à possível toxicidade dos antioxidantes sintéticos e à demanda atual por produtos mais saudáveis, o uso de antioxidantes naturais, como o extrato de semente e casca de uva, representa uma alternativa na prevenção da oxidação lipídica em carne de frango, além de permitir aproveitamento do resíduo do processamento do vinho e suco de uva. Assim, o objetivo deste trabalho foi avaliar extratos de bagaço de uva (sementes e cascas) das variedades Isabel e Niágara (Vitis labrusca L.) quanto à atividade antioxidante em carne de frango processada crua e cozida. Foram adicionados à carne de frango 4 tipos de antioxidantes: butilhidroxitolueno; mistura comercial de eritorbato de sódio, ácido cítrico e açúcar; extrato de semente e casca de uva Isabel; extrato de semente e casca de uva Niágara; além do tratamento controle, sem antioxidante. A carne de frango foi processada no formato de mini-hambúrgueres, embalada a vácuo e armazenada sob congelamento (-18°C), durante 9 meses. As amostras foram caracterizadas através da determinação da composição centesimal. A cada três meses, foram realizadas análises de pH, cor instrumental, avaliação microbiológica, oxidação lipídica (valor das substâncias reativas ao ácido tiobarbitúrico TBARS) e análise sensorial. Não foi verificada alteração significativa (p>0,05) na composição centesimal e no valor de pH de amostras cruas e cozidas, em nenhum dos tratamentos analisados. Ambos os extratos de bagaço de uva mostraram efeito na inibição da oxidação lipídica da carne de frango crua e cozida, apresentando resultados comparáveis aos antioxidantes sintéticos utilizados. Houve interferência dos extratos de bagaço de uva na coloração da carne de frango cozida. Na análise de cor objetiva, os tratamentos com extrato de semente e casca de uvas Isabel e Niágara apresentaram-se mais escuros, menos avermelhados e com menor intensidade de cor amarela e, na análise subjetiva, as notas destes tratamentos, para o atributo alteração de cor, foram significativamente maiores (p<0,05) que as dos demais tratamentos. A coloração da carne de frango crua não foi afetada pela adição dos extratos. Através da análise sensorial, o extrato de bagaço de uva Isabel causou menor alteração no sabor e odor da carne de frango, apresentando resultados semelhantes aos antioxidantes sintéticos. Os resultados da análise microbiológica indicaram que as amostras de todos os tratamentos apresentaram-se dentro dos padrões estabelecidos pela legislação brasileira. A utilização de bagaço da indústria vinícola (semente e casca) como antioxidante natural, combinado com o uso da embalagem a vácuo e armazenamento congelado, pode ser considerada um método eficiente para retardar a oxidação lipídica de carne de frango processada, tanto crua, como cozida. Entretanto mais estudos devem ser conduzidos a fim de aprimorar a compatibilidade dos extratos ao produto, buscando minimizar suas interferências nas características sensoriais e organolépticas. / Chicken meat, due to the high concentration of unsaturated fatty acids, is highly susceptible to lipid oxidation, which affects taste, aroma, colour and texture of foods, limiting its stability and shelf-life. Due to the possible toxicity of synthetic antioxidants and the current demand for healthier products, the use of natural antioxidants, such as grape seed and peel extract, is an alternative in the prevention of lipid oxidation in chicken meat, and allows the use of residues from wine and grape juice processing. Thus, the objective of this study was to evaluate grape pomace extracts (seeds and peels) of Isabel and Niagara varieties (Vitis labrusca L.) on the antioxidant activity in raw and cooked processed chicken meat. Four types of antioxidants were added to chicken meat: butylhydroxytoluene; commercial mixture of sodium erythorbate, citric acid and sugar; Isabel grape seed and peel extract; Niagara grape seed and peel extract; and the control, without antioxidant. The chicken meat was processed in the form of mini-burgers, vacuum packaged and stored under freezing (-18°C) for 9 months. The samples were characterized by determining the proximate composition. Every three months, the following analyses were carried out: pH, instrumental color, microbiological evaluation, lipid oxidation (value of thiobarbituric acid reactive substances - TBARS) and sensory analysis. No significant changes (p>0.05) in proximate composition and pH values were observed for raw and cooked samples, in none of the treatments. Both grape pomace extracts showed effect on inhibiting lipid oxidation in raw and cooked chicken meat, with results comparable to synthetic antioxidants used. There was interference from grape pomace extracts in the color of cooked chicken meat. In the objective color analysis, Isabel and Niagara grape seed and peel extract treatments were darker, less red and with less intense yellow color, and in the subjective analysis, the scores for these treatments, for attribute color alteration, were significantly higher (p<0.05) than the other treatments. The color of raw chicken meat was not affected by the addition of extracts. Through sensory evaluation, the Isabel grape pomace extract caused less change in taste and odour of chicken meat, with results similar to synthetic antioxidants. The results of microbiological analysis indicated that samples from all treatments were within the standards established by Brazilian legislation. The use of pomace from the wine industry (seeds and peels) as natural antioxidant, combined with the use of vacuum packaging and frozen storage, can be considered an effective method to retard lipid oxidation in processed chicken meat, both raw and cooked. However, further studies should be conducted in order to improve the compatibility of the extracts to the product, aiming to minimize its interference in the sensorial and organoleptic characteristics.

A carne de frango, em razão da elevada concentração de ácidos graxos insaturados, é altamente suscetível ao processo de oxidação lipídica, que afeta sabor, aroma, cor e textura dos alimentos, limitando sua estabilidade e vida-útil. Devido à possível toxicidade dos antioxidantes sintéticos e à demanda atual por produtos mais saudáveis, o uso de antioxidantes naturais, como o extrato de semente e casca de uva, representa uma alternativa na prevenção da oxidação lipídica em carne de frango, além de permitir aproveitamento do resíduo do processamento do vinho e suco de uva. Assim, o objetivo deste trabalho foi avaliar extratos de bagaço de uva (sementes e cascas) das variedades Isabel e Niágara (Vitis labrusca L.) quanto à atividade antioxidante em carne de frango processada crua e cozida. Foram adicionados à carne de frango 4 tipos de antioxidantes: butilhidroxitolueno; mistura comercial de eritorbato de sódio, ácido cítrico e açúcar; extrato de semente e casca de uva Isabel; extrato de semente e casca de uva Niágara; além do tratamento controle, sem antioxidante. A carne de frango foi processada no formato de mini-hambúrgueres, embalada a vácuo e armazenada sob congelamento (-18°C), durante 9 meses. As amostras foram caracterizadas através da determinação da composição centesimal. A cada três meses, foram realizadas análises de pH, cor instrumental, avaliação microbiológica, oxidação lipídica (valor das substâncias reativas ao ácido tiobarbitúrico TBARS) e análise sensorial. Não foi verificada alteração significativa (p>0,05) na composição centesimal e no valor de pH de amostras cruas e cozidas, em nenhum dos tratamentos analisados. Ambos os extratos de bagaço de uva mostraram efeito na inibição da oxidação lipídica da carne de frango crua e cozida, apresentando resultados comparáveis aos antioxidantes sintéticos utilizados. Houve interferência dos extratos de bagaço de uva na coloração da carne de frango cozida. Na análise de cor objetiva, os tratamentos com extrato de semente e casca de uvas Isabel e Niágara apresentaram-se mais escuros, menos avermelhados e com menor intensidade de cor amarela e, na análise subjetiva, as notas destes tratamentos, para o atributo alteração de cor, foram significativamente maiores (p<0,05) que as dos demais tratamentos. A coloração da carne de frango crua não foi afetada pela adição dos extratos. Através da análise sensorial, o extrato de bagaço de uva Isabel causou menor alteração no sabor e odor da carne de frango, apresentando resultados semelhantes aos antioxidantes sintéticos. Os resultados da análise microbiológica indicaram que as amostras de todos os tratamentos apresentaram-se dentro dos padrões estabelecidos pela legislação brasileira. A utilização de bagaço da indústria vinícola (semente e casca) como antioxidante natural, combinado com o uso da embalagem a vácuo e armazenamento congelado, pode ser considerada um método eficiente para retardar a oxidação lipídica de carne de frango processada, tanto crua, como cozida. Entretanto mais estudos devem ser conduzidos a fim de aprimorar a compatibilidade dos extratos ao produto, buscando minimizar suas interferências nas características sensoriais e organolépticas. / Chicken meat, due to the high concentration of unsaturated fatty acids, is highly susceptible to lipid oxidation, which affects taste, aroma, colour and texture of foods, limiting its stability and shelf-life. Due to the possible toxicity of synthetic antioxidants and the current demand for healthier products, the use of natural antioxidants, such as grape seed and peel extract, is an alternative in the prevention of lipid oxidation in chicken meat, and allows the use of residues from wine and grape juice processing. Thus, the objective of this study was to evaluate grape pomace extracts (seeds and peels) of Isabel and Niagara varieties (Vitis labrusca L.) on the antioxidant activity in raw and cooked processed chicken meat. Four types of antioxidants were added to chicken meat: butylhydroxytoluene; commercial mixture of sodium erythorbate, citric acid and sugar; Isabel grape seed and peel extract; Niagara grape seed and peel extract; and the control, without antioxidant. The chicken meat was processed in the form of mini-burgers, vacuum packaged and stored under freezing (-18°C) for 9 months. The samples were characterized by determining the proximate composition. Every three months, the following analyses were carried out: pH, instrumental color, microbiological evaluation, lipid oxidation (value of thiobarbituric acid reactive substances - TBARS) and sensory analysis. No significant changes (p>0.05) in proximate composition and pH values were observed for raw and cooked samples, in none of the treatments. Both grape pomace extracts showed effect on inhibiting lipid oxidation in raw and cooked chicken meat, with results comparable to synthetic antioxidants used. There was interference from grape pomace extracts in the color of cooked chicken meat. In the objective color analysis, Isabel and Niagara grape seed and peel extract treatments were darker, less red and with less intense yellow color, and in the subjective analysis, the scores for these treatments, for attribute color alteration, were significantly higher (p<0.05) than the other treatments. The color of raw chicken meat was not affected by the addition of extracts. Through sensory evaluation, the Isabel grape pomace extract caused less change in taste and odour of chicken meat, with results similar to synthetic antioxidants. The results of microbiological analysis indicated that samples from all treatments were within the standards established by Brazilian legislation. The use of pomace from the wine industry (seeds and peels) as natural antioxidant, combined with the use of vacuum packaging and frozen storage, can be considered an effective method to retard lipid oxidation in processed chicken meat, both raw and cooked. However, further studies should be conducted in order to improve the compatibility of the extracts to the product, aiming to minimize its interference in the sensorial and organoleptic characteristics.

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Bacterial responses to environmental stresses may be easily observed and predicted under controlled laboratory conditions. However, realistic conditions encountered during manufacturing, in retail or in households may cause unpredicted responses of spoilage or pathogenic bacteria. Therefore it is essential to identify and understand the microbial dynamics under such conditions. The overall aim of the present study was to simulate the most common environmental conditions and consumer-style practices during storage or preparation of Ready-to-Eat (RTE) and Ready-to-Cook (RTC) products in the domestic environment, and predict the microbial dynamics which may deteriorate the quality or compromise the safety of these foods. Aiming to develop a unified mathematical model for the prediction of the growth of the specific spoilage microorganisms (SSOs), the spoilage pattern of three RTE acidic spreads of low pH was described in relation to microbial, physicochemical and molecular changes during storage. Results showed that the spoilage profile of the products was primarily affected by the initial pH and the storage temperature, despite the differences in their formulation. These findings enabled the assessment of two unified models (polynomial and Ratkowsky) for the prediction of the growth of lactic acid bacteria (LAB; SSOs) in such acidic spreads, using only the initial pH, the concentration of undissociated acetic acid and the storage temperature. The models were validated under realistic conditions in household refrigerators. Despite the abrupt fluctuations of the temperature during validation procedure, they both were able to adequately predict the growth of LAB in the spreads. However, the initial contamination level was proved to be necessary and crucial for the accurate prediction of microbial dynamics. The time-temperature profiles of the validation procedure revealed that the suggested storage conditions were not followed promptly and, therefore, concerns were raised on the effect of such consumer mishandlings on the safety of foods. Therefore, the responses of Salmonella spp. and Escherichia coli O157:H7 to the stresses encountered during frozen storage, thawing and cooking of ground beef, simulating typical scenarios followed by the consumers, were evaluated. The results revealed that the guidelines issued by the food safety authorities lack of some specific points that may affect the safety of the final product, such as the duration of frozen storage and the method of cooking. In particular, it was found that the heat resistance of E. coli O157:H7 was likely increased after long term frozen storage, while cooking in pan-grill did not ensure the safety of the final product, even when cooked at the suggested temperature. As shown in the first study, the initial contamination level played a significant role on the predictions of the models and further on the shelf-life of the products. Therefore, the dynamics of realistically low initial populations of Listeria monocytogenes and Salmonella Typhimurium versus higher levels of the pathogens (such those used during in vitro trials) in RTE fresh-cut salads were compared. In addition, any potential uncertainty sources for the growth potential of the pathogens in broth-based simulations were investigated. Results showed that the growth variability of low inocula is highly affected by the marginal storage temperatures, the indigenous microflora and the availability of nutrients. Because of this, growth from low populations showed the likelihood to exceed the growth derived from unrealistically high inocula, suggesting that ―fail-dangerous‖ implications may derive from such challenge tests. Data derived from this part were compared with broth-based simulations and the results showed that high uncertainty should be expected when extrapolating such predictions from low initial populations in fresh-cut salads, due to the various factors affecting the microbial growth on a real food, which are (inevitably) ignored by broth-based models. Overall, the present Thesis highlights the significant impact of consumer mishandlings on the food safety and quality of foods and contributes to the identification of unpredicted potential risk origins in the domestic environment.

No description available.