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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

Changes in the chemical and physico-chemical characteristics of the guava juice (Psidium guajava L.) during processing. / AlateraÃÃes das caracterÃsticas quÃmicas e fÃsico-quÃmicas do suco de goiaba (Psidium guajava L.) durante o processamento

Aline Gurgel Fernandes 27 February 2007 (has links)
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Os sucos de frutas sÃo importantes fontes de vitaminas, sais minerais, Ãcidos orgÃnicos e fibras, e incluÃdos na dieta da populaÃÃo podem ajudar a manter a saÃde. Durante as etapas de processamento de sucos, podem ocorrer modificaÃÃes nos componentes dos frutos, afetando suas propriedades sensoriais e nutritivas. Estudos sobre os efeitos do processamento nos constituintes nutricionais dos sucos tropicais sÃo escassos. Geralmente, sÃo avaliadas somente as perdas de vitamina C. Este trabalho objetivou determinar as possÃveis alteraÃÃes quÃmicas e fÃsico-quÃmicas em suco tropical de goiaba durante as etapas de processamento (extraÃÃo, formulaÃÃo / homogeneizaÃÃo e pasteurizaÃÃo) e armazenamento (30 dias). Foram efetuadas determinaÃÃes de sÃlidos solÃveis, pH, acidez, aÃÃcares redutores, aÃÃcares totais, atividade de Ãgua, cor, vitamina C, antocianinas, carotenÃides, compostos fenÃlicos e atividade da pectinametilesterase. Ao final do estudo, constatou-se que somente os parÃmetros de pH, carotenÃides e atividade da pectinametilesterase apresentaram variaÃÃes significativas, durante as etapas de processamento do suco. O suco de goiaba se manteve ao final do processamento com elevados teores de vitamina C, compostos fenÃlicos, antocianinas totais, alÃm do aumento da quantidade de carotenÃides totais. No suco de goiaba armazenado por 30 dias observou-se que os parÃmetros analisados nÃo apresentaram diferenÃa significativa entre o tempo zero e o trinta dias. Concluindo que as caracterÃsticas quÃmicas e fÃsico-quÃmicas sÃo pouco afetadas pelo processamento e armazenamento (30 dias), pode-se considerar, portanto o processo de enchimento à quente (hot fill), as embalagens de vidro utilizadas e os conservantes adicionados como sendo bons fatores de preservaÃÃo para o produto em estudo. / Fruit juices are important vitamin sources, mineral salts, organic acids and fibers, and including in the diet of the population, they can help to keep people healthy. During the stages of juice processing, some modifications in the fruit compounds can happen, affecting its sensorial and nutritional properties. Researches on the effects of processing on the nutritional compound tropical juice are scarce. Usually, only vitamin C losses are evaluated. This study determined the possible chemical and physical-chemical changes during the stages of guava tropical juice processing (extration, formulation / homogenization and pausterization) and storage (30 days). Soluble solids, pH, acidity, reducing sugars, total sugars, water activity, colour, vitamin C, anthocyanins, carotenoids, phenolic compounds and pectinametilesterase activity were analysed. We saw that only pH, carotenoids and pectinametilesterase activity parameters showed significant variations during the stages of juice processing. At the end of the processing, vitamin C, phenolic compounds and total anthocyanins contents were high, and it was an increase of total carotenoid amount in the guava juice. For the guava juice stored during 30 days it was observed no significant difference between the times zero and thirty days, for the analysed parameters. We conclude that since the chemical and physicochemical characteristics were affected just a little by processing and stored during 30 days, the hot fill processing, the glass packings used and added conservant were good factors of product preservation in this study.

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