Rheological behavior and color stability of anthocyanins from Merlot (Vitis vinifera L.) and Bordô (Vitis labrusca L.) grapes in a jam model system

Abstract

IntroductionColor is an important factor in the consumers' choice of food products. It is one of the most important characteristics used to define the quality of food and has a decisive influence on the acceptance by the consumer (BLENDFORD, 1995;HENDRY and HOUGHTON, 1996).The replacement of synthetic colorants with natural ones as food additives has substantially increased worldwide and anthocyanins are considered an attractive option for use in foods due to their bright and attractive colors. Also, these pigments display a remarkable number of biochemical and pharmacological activities and many of their pharmacological properties have been correlated to the scavenging ability of oxygen-generated free radicals and to the inhibition of lipid peroxidation (TSUDA et al., 1994;SATUÉ-GRACIA;HEINONEN;FRANKEL, 1997); thus, the incorporation of anthocyanins into a variety of food systems is desirable.Anthocyanins are a group of well-known water-soluble pigments, which contribute significantly to the red-blue coloration of many flowers, fruits, and vegetables. These pigments are glycosides of polyhydroxy and polymethoxy derivatives of the 3,5,7,3-tetrahydroxyflavylium cation and are classified as flavonoids. An anthocyanin molecule comprises an aglycone or anthocyanidin moiety, which is glycosylated in its natural state by one or more sugars. The electron deficiency of the flavylium cation makes the free aglycones (anthocyanidins) highly reactive and instable and they do not occur naturally (MAZZA; MINIATI, 1993). ResumoAs antocianinas, pigmentos responsáveis pela cor vermelha das uvas, são facilmente degradadas por vários mecanismos de reação, através da ação do oxigênio, enzimas, pH e temperatura, entre outras variáveis. Neste trabalho, um sistema modelo de geleia foi desenvolvido utilizando extrato de uva das variedades Bordô e Merlot e polissacarídeos (gomas xantana e locusta) em diferentes temperaturas (45, 55 e 65 °C). A estabilidade dos pigmentos antociânicos e o comportamento reológico foram estudados. Para a determinação da estabilidade, calculou-se o tempo de meia-vida (t½) e a constante velocidade de reação (primeira ordem) (k). Para o comportamento reológico, as constantes foram determinadas utilizando-se o modelo matemático Power law. O sistema modelo desenvolvido que utiliza a temperatura de 45 °C mostrou os melhores resultados para o t½ das antocianinas. Os valores de k para os tratamentos 45, 55 e 65 °C não foram significativos (p > 0,05). Observou-se que com o aumento da temperatura de desenvolvimento do sistema modelo de geleia houve um aumento no índice da consistência. Palavras-chave: Vitis vinifera L.; Vitis labrusca L.; antocianina; goma xantana; comportamento reológico. AbstractAnthocyanins are the pigments responsible for the color of most red grapes and are easily degraded following various reaction mechanisms affected by oxygen, enzymes, pH, and temperature among other variables. In this study, a jam model system was developed using Merlot and Bordô grape extracts and polysaccharides (xanthan a...

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