Thermal and pH stability of natural anthocyanin colourant preparations from black goji berry

Abstract

This study investigated the pH and thermal stability of black goji berry anthocyanins and compared them to purple sweet potato anthocyanins for application as natural colourants. The effect of pH (3, 4, 5, and 6) treatment followed by storage at 4 and 26 °C for 30 days and thermal treatments (60, 80, and 100 °C) for 10 and 30 min on the stability of colourant preparations from black goji berry and purple sweet potato were determined. The total anthocyanin content, total phenolic content, antioxidant activity, and colour were measured after thermal treatment and at 6 days intervals for 30 days storage after pH treatments. LC-MS analysis was carried out at the end of each treatment. Petunidin-3-O-rutinoside(trans-p-coumaroyl)-5-O-glucoside accounted for 71% of identified anthocyanins. The colourant preparations from black goji berry demonstrated high stability at 60 °C for 10 and 30 min and high storage stability at pH 3 at 4 °C storage for 30 days. The colourant preparations from black goji berry had higher colour stability than purple sweet potato upon thermal treatments but lower stability during storage at 4 and 26 °C. This study demonstrated the potential of anthocyanins from black goji berry as a natural colourant.