Effects of casein‐ and whey protein–dextran conjugates on the stability of bog bilberry anthocyanin extract

Abstract

SummaryBog bilberry (Vaccinium uliginosum) contains a high concentration of anthocyanins. Anthocyanin stability depends on many factors, including pH, temperature and composition of food matrices in a product, such as protein and polysaccharide. The effect of casein–dextran and whey protein–dextran conjugates on the stability of bog bilberry anthocyanin extract (BBAE) was investigated in an accelerated model system. Cyanidin‐3‐glucoside was the main anthocyanin (79%) found in BBAE. The cyanidin‐3‐glucoside content, absorbance and ABTS [2, 2‐Azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt] radical scavenging activity of BBAE significantly (P < 0.05) decreased after heating at pH 8.0 and 80 °C for 60 min. The addition of casein–dextran and whey protein–dextran conjugates significantly (P < 0.05) prevented cyanidin‐3‐glucoside from degradation, and increased the absorbance and ABTS radical scavenging activity of heated BBAE. The protection of casein–dextran conjugate on BBAE was significantly higher (P < 0.05) than that of whey protein–dextran conjugate. The results suggest that protein–dextran conjugates have the ability to stabilise BBAE.