Effects of low power ultrasonic treatment on the transformation of cyanidin-3-O-glucoside to methylpyranocyanidin-3-O-glucoside and its stability evaluation.

Pyranoanthocyanins are anthocyanin derivatives that are formed during fermentation and oxygenation processes in aged wine. They play a critical role in assessing the aging of wine based on its colour quality. Naturally, the formation process of pyranoanthocyanins is fairly slow. In this respect, the present work studies the role and efficiency of ultrasonic treatment in accelerating the formation of methylpyranocyanidin-3-O-glucoside and investigates the spectral characteristics as well as the stability of this derivative toward heat, bisulfite bleaching and pH variation in a simulation system. Our results showed that the yield of methylpyranocyanidin-3-O-glucoside can be increased by 32.5% by ultrasonic treatment at 100 W for 40 min, and excessive treatment (≥60 min) does not have a positive effect on the yield. Moreover, this derivative exhibits a better stability toward heat, pH variation and bisulfite bleaching than its precursor cyanidin-3-O-glucoside.