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

Anthocyanins 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 Bordo grape extracts and polysaccharides (xanthan and locust bean gums) and different temperatures (45, 55 and 65 degrees C). The stability of the anthocyanin pigments and the rheological behavior of the jam model system were studied. For the determination of the stability, the half-life time and first-order reaction rate constants for the anthocyanin pigments were calculated. The rheological behavior was determined through the Power law model. The jam model system produced using a temperature of 45 degrees C showed the best results for the anthocyanin half-life time. The first-order reaction rate constants for the 45, 55, and 65 degrees C treatments were not significantly different among each other (p > 0.05). It was observed that with an increase in the jam model system temperature there was an increase in the index of consistency.