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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Efeito da radiaÃÃo gama sobre a reduÃÃo de microrganismos patogÃnicos, a estabilidade dos lipÃdios e as caracterÃsticas sensoriais em caudas de camarÃes congelados / Effect of gamma radiation in the reduction of pathogenic microorganisms, the stability of the lipids and the sensory characteristics in frozen shrimp tails

VirgÃnia Kelly GonÃalves Abreu 30 August 2006 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A irradiaÃÃo representa uma tÃcnica eficiente na conservaÃÃo dos alimentos, e o interesse pela sua utilizaÃÃo tem crescido nos Ãltimos anos, pois alÃm de melhorar a qualidade microbiolÃgica, produz mÃnimas alteraÃÃes nos constituintes dos alimentos. Sendo assim, este trabalho teve como objetivo estudar o efeito da radiaÃÃo gama (60Co), aplicada ao camarÃo congelado e embalado, sobre a microbiota, a estabilidade quÃmica de alguns componentes, bem como sobre algumas propriedades sensoriais da carne. Foram avaliadas caudas de camarÃes da espÃcie Penaeus vannamei, provenientes da carcinicultura local. O estudo foi dividido em duas etapas, sendo a primeira destinada a verificar o efeito da radiaÃÃo gama, aplicada nas doses de 0, 2, 4 e 6kGy, sobre a populaÃÃo de duas bactÃrias patogÃnicas inoculadas no camarÃo: Vibrio cholerae O1 e Salmonella enteritidis. Este estudo utilizou um delineamento experimental inteiramente casualizado, em esquema fatorial 4 x 3, em que os fatores avaliados foram as quatro doses de irradiaÃÃo e trÃs modalidades de inoculaÃÃo (com V. cholerae O1, com S. enteritidis e sem inoculaÃÃo de microrganismos). Jà na segunda etapa foi usado um delineamento experimental inteiramente casualizado, em esquema fatorial 4 x 5, sendo quatro doses (0, 2, 4 e 6kGy) de irradiaÃÃo e cinco repetiÃÃes, para as anÃlises de substÃncias reativas ao Ãcido tiobarbitÃrico (TBARS), cor e textura instrumental. Para a anÃlise sensorial foi utilizado um delineamento de blocos completos balanceados, onde o provador foi considerado como bloco. Houve uma reduÃÃo significativa (p<0,05) do nÃmero de V. cholerae O1 e de S. enteritidis de acordo com o aumento da dose de irradiaÃÃo. Em relaÃÃo aos valores de TBARS, houve um decrÃscimo (p<0,05) das amostras irradiadas com 6kGy em relaÃÃo as nÃo irradiadas. Quanto ao valor do componente de cor L* houve uma elevaÃÃo significativa (p<0,05) com a dose de 6kGy em relaÃÃo à dose de 2kGy. Os componentes de cor a* e b* e a textura instrumental nÃo variaram (p>0,05) com as doses de irradiaÃÃo estudadas. Com relaÃÃo as caracterÃsticas sensoriais, a aceitaÃÃo global apresentou uma reduÃÃo significativa (p<0,05) com a dose 6kGy quando comparada com as doses 0 e 2kGy. No entanto, os atributos de aceitaÃÃo de cor e textura e a intensidade dos atributos aroma, sabor caracterÃstico e suculÃncia nÃo foram afetados (p>0,05). Desta forma, o tratamento de irradiaÃÃo com atà 6kGy mostra-se efetivo na reduÃÃo de microrganismos patogÃnicos, com leves efeitos sobre as caracterÃsticas sensoriais da carne, quando aplicado sobre o camarÃo congelado e embalado. / Irradiation represents an efficient technique to extend shelf life of several foods and the interest in using this technology has been growing in the last years because besides improving food safety it produces minimal alterations in the food constituents. Thus, this study investigated the effect of ionizing irradiation (60Co) of frozen and packaged shrimp on microorganisms as well as on some chemical and sensory characteristics of the product. Cultivated shrimp (Penaeus vannamei) from local farms processed into shrimp tails were packaged, frozen, irradiated and analyzed. The study was divided in two stages. The first stage was intended to verify the effect of the gamma radiation on the population of inoculated Vibrio cholerae O1 and Salmonella enteritidis bacteria. It used a complete randomized factorial (4 x 3) design with four irradiation doses (0, 2, 4 and 6kGy) and three inoculation modalities (one with V. cholerae O1, one with S. enteritidis and one without microorganisms). The second stage aiming to verify the effect of the gamma irradiation on the chemical stability of lipids, color and instrumental texture of shrimp followed a complete randomized factorial (4 x 5) design with four irradiation doses (0, 2, 4, and 6kGy) and five replicates. Sensorial analysis followed a complete randomized factorial of balanced complete blocks, where the panelist was considered as block. The experimental units (UE) from the first stage were analyzed for V. cholerae O1 and S. enteritidis survival after the irradiation procedure, while those from the second stage were analyzed for thiobarbituric acid reactive substances (TBARS), instrumental color and texture and sensory evaluation of the meat. As irradiating dose increased a significant (p<0.05) reduction in V. cholerae O1 and S. enteritidis counts was observed. TBARS values decreased (p<0.05) in shrimp irradiated with 6kGy related to those in non irradiated shrimp. Also, color component L* increased (p<0.05) in shrimp irradiated with 6kGy dose as compared to that irradiated with the 2kGy dose. No effect of irradiation was found on color components a* and b* or on instrumental texture values. Sensory global acceptance presented a significant reduction (p <0.05) with the dose of 6kGy as related to the doses of 2kGy or 0kGy. However, color acceptance and texture and the intensity of the attributes aroma, flavor and juiciness were not affected (p>0.05). Therefore, irradiation treatment in doses up to 6kGy on frozen and packaged shrimp tails significantly reduces V. cholerae O1 and S. enteritidis counts with minor effects on sensory characteristics in cooked shrimp.

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