Effect of whey protein isolate and phenolic copigments in the thermal stability of mulberry anthocyanin extract at an acidic pH

Abstract

This study investigated the effect of whey protein isolate (WPI) and phenolic copigments on the color and anthocyanin stability of mulberry anthocyanin extract (MAE) subjected to heat treatment (80℃/120 min) at pH 3.6. Results showed that four phenolic compounds, including gallic acid, ferulic acid, (-)-epigallocatechin gallate (EGCG), and rutin, significantly affected the color enhancement of MAE solution, among which the strongest copigmentation effect on MAE was observed for rutin at 0.08-0.8 mg/ml. WPI (0.16 mg/ml) and rutin (0.8 mg/ml) reduced the thermal degradation rate of total anthocyanins by 27.1% and 50%, respectively. WPI-MAE-rutin ternary mixtures improved the color stability of MAE solution and decreased the anthocyanin's thermal degradation rate by 18.1% and 10.6%, respectively, compared with the corresponding binary systems (MAE-WPI and MAE-rutin). The results implied the MAE-WPI-rutin had a better protective effect on the thermal stability of MAE than the binary systems.

Keywords: Mulberry anthocyanin extract; Phenolic copigment; Ternary mixture; Thermal stability; Whey protein isolate.