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Efeito da aplicação de revestimentos comestíveis enriquecidos em antioxidantes na conservação de frutos minimamente processados
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Os frutos frescos cortados ou minimamente processados apresentam uma actividade fisiológica acrescida relativamente aos frutos, o que conduz a alterações substanciais de cor e firmeza, entre outras. A maçã reineta minimamente processada caracteriza-se por apresentar níveis de escurecimento elevados durante o processamento mínimo e ao longo do armazenamento. Atendendo ao interesse comercial em produzir maçã reineta minimamente processada de qualidade e com um período de vida útil adequado, este trabalho teve por objectivo desenvolver metodologias que permitam manter níveis de qualidade elevados, por um período de vida útil compatível com o circuito comercial. Avaliou-se o impacto da aplicação de revestimentos comestíveis hidrocoloidais, adicionados ou não de agentes anti-escurecimento, bem como a aplicação destes agentes isoladamente. Foram ainda testadas metodologias físicas (choque térmico e pré tratamento térmico moderado). O efeito das diferentes barreiras foi avaliado após processamento mínimo e ao longo do armazenamento sob refrigeração. A aplicação dos revestimentos testados não se revelou eficaz no caso do fruto em estudo. Das várias metodologias testadas verificou-se que a mais eficaz foi a aplicação de tratamento químico por imersão em solução antioxidante com uma concentração de 0,5% de L-cisteína e 2% de ácido cítrico, durante dois minutos. Este tratamento permitiu preservar a cor da maçã reineta minimamente processada durante 3 dias de armazenamento em câmara a 4ºC e com humidade relativa superior a 90%.
Minimally processed or fresh-cut fruits present added physiological activity over unprocessed fruits, which leads to substantial changes in colour and firmness, among others. The Reinette apple is known for presenting high levels of browning during minimal processing and throughout storage. Bearing in mind the commercial interests in producing minimally processed high-quality Reinette apple with an adequate shelf-life, it was this essay's goal to develop methods to enable the maintenance of high quality levels, for a shelf-life compatible with the commercial circuit. It was this essay's goal to develop methods to enable high quality levels in minimally processed Reinette apple, so as to achieve a useful lifespan in commercial circuits. It was evaluated the impact of applying hydrocolloidal edible coatings, with or without added antibrowning agents, as well as their separate application. The effect of the different barriers applied separately or in combination was evaluated after minimal processing and throughout storage under refrigeration. Physical methods such as thermal shock and mild heat pre-treatments were also tested. The application of the evaluated coatings did not prove to be effective in the case of the fruit in question. Among the various methods was verified that the most effective one to be the application of a chemical treatment by immersion in an antioxidant solution with a concentration of 0,5% LCystein and 2% citric acid, for two minutes. This treatment allowed to preserve the minimally processed Reinette apple's colour for 3 days of storage in a chamber at 4ºC with relative humidity above 90%.
Minimally processed or fresh-cut fruits present added physiological activity over unprocessed fruits, which leads to substantial changes in colour and firmness, among others. The Reinette apple is known for presenting high levels of browning during minimal processing and throughout storage. Bearing in mind the commercial interests in producing minimally processed high-quality Reinette apple with an adequate shelf-life, it was this essay's goal to develop methods to enable the maintenance of high quality levels, for a shelf-life compatible with the commercial circuit. It was this essay's goal to develop methods to enable high quality levels in minimally processed Reinette apple, so as to achieve a useful lifespan in commercial circuits. It was evaluated the impact of applying hydrocolloidal edible coatings, with or without added antibrowning agents, as well as their separate application. The effect of the different barriers applied separately or in combination was evaluated after minimal processing and throughout storage under refrigeration. Physical methods such as thermal shock and mild heat pre-treatments were also tested. The application of the evaluated coatings did not prove to be effective in the case of the fruit in question. Among the various methods was verified that the most effective one to be the application of a chemical treatment by immersion in an antioxidant solution with a concentration of 0,5% LCystein and 2% citric acid, for two minutes. This treatment allowed to preserve the minimally processed Reinette apple's colour for 3 days of storage in a chamber at 4ºC with relative humidity above 90%.
Descrição
Tese de mestrado em Controlo da Qualidade e Toxicologia dos Alimentos apresentada à Universidade de Lisboa através da Faculdade de Farmácia, 2007
Palavras-chave
Alimentação e nutrição Controlo de qualidade Teses de mestrado - 2007