Índice de polifenóis, antocianinas totais e atividade antioxidante de um sistema modelo de geléia de uvas

Abstract

*A quem a correspondência deve ser enviada ResumoAntocianinas são pigmentos fenólicos com potencial para substituição dos corantes artificiais vermelhos; porém, estes se apresentam instáveis frente ao processamento de alimentos, sendo a temperatura um dos principais fatores envolvidos na degradação da cor destes pigmentos. O objetivo deste trabalho foi avaliar a concentração de compostos fenólicos e a capacidade antioxidante de um sistema modelo de geléia de uvas (SMG) Isabel (Vitis labrusca) e Refosco (Vitis vinifera L.) elaborado a 45 °C, utilizando como agente espessante uma mistura de gomas xantana e locusta. Nos SMGs elaborados, avaliou-se a estabilidade dos pigmentos antociânicos e determinou-se polifenóis totais (IPT), antocianinas totais (AT). A atividade antioxidante foi medida utilizando os métodos de captura de radicais estáveis como o radical DPPH (2,2-difenil-1-picril-hidrazila) e o radical ABTS (2,2'-azino-bis-(3-etilbenzotiazolina-6-ácido sulfônico)). Avaliou-se também a concentração de AT nos extratos de uvas utilizados na elaboração do SMG. Um alto coeficiente de correlação foi encontrado entre AT e IPT dos SMGs e a atividade antioxidante. Os melhores resultados quanto à concentração de IPT, AT e em relação à atividade antioxidante foram obtidos para o SMG elaborado com uva Refosco. O método utilizado para a elaboração dos SMGs foi efetivo na preservação da cor antocianinas e das propriedades antioxidantes dos compostos fenólicos totais avaliados. Palavras-chave: uva; antocianinas; compostos fenólicos; atividade antioxidante; estabilidade. AbstractAnthocyanins are phenolic pigments with a potential for replacing synthetic red dyes. However, their stability is affected by food processing, and temperature is one of the main factors involved in these pigments' color degradation. The aim of this work was to evaluate the concentration of phenolic compounds and the antioxidant capacity of a grape jelly model system (JMS). The grape varieties used here were Isabel (Vitis labrusca) and Refosco (Vitis vinifera L.) and the jelly was cooked at 45 °C, using a mixture of xanthan gum and locust bean gum as the thickening agent. Two JMSs were prepared and analyzed to determine their anthocyanin stability, total polyphenol index (TPI) and total anthocyanin content (TA). The antioxidant activity was measured by the DPPH and ABTS radical-scavenging methods. The TA concentration was also determined in the grape extracts used in the preparation of the JMSs. The best results in terms of TPI, TA and antioxidant activity were obtained for the JMS produced with Refosco grapes. A high correlation coefficient was found between the TA and TPI in the JMSs and the antioxidant activity. The method used in the production of the JMSs was effective in preserving the color of anthocyanins and the antioxidant properties of the total phenolic compounds evaluated here. Keywords: grape; anthocyanins; phenolic compounds; antioxidant activity; stability.Índice de polifenóis, antocianinas totais e atividade antioxidante de um sistema m...

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