The effect of whey protein concentration and preheating temperature on the color and stability of purple corn, grape and black carrot anthocyanins in the presence of ascorbic acid.

Our objective was to explore the effects of whey protein (WP) concentration and preheating temperature on anthocyanin color expression and stability over time in the presence of ascorbic acid. Anthocyanins from purple corn, grape or black carrot were mixed with native WP or preheated WP (40-80°C) in various concentrations (0-10 mg/mL) in pH 3 buffer containing 0.05% ascorbic acid and stored in the dark at 25 °C for 5 days. WP addition increased anthocyanin absorbance and protected anthocyanin from ascorbic acid-mediated degradation. Increasing WP concentration resulted in lower lightness and higher chroma, hue angle and color stability. The color loss of anthocyanin solutions decreased by 40%-50% when 10 mg/mL WP was added. Native WP showed more color enhancement and protection than thermally-induced WP. Increasing the WP preheating temperature resulted in less absorbance increase and more absorbance loss. Anthocyanin' half-life was improved by addition of WP in a dose dependent manner. Native WP addition (10 mg/mL) extended anthocyanin half-life by about 2 times for purple corn and grape, and 1.31 times for black carrot anthocyanin solutions. Preheating temperature did not significantly affect anthocyanin protection by WP. WP addition might enhance anthocyanin stability in beverages containing ascorbic acid, expanding anthocyanin application in foods.