Effect of thermosonication and thermal treatments on phytochemical stability of barberry juice copigmented with ferulic acid and licorice extract

This study was designed to compare the effect of thermosonication and thermal treatment on color and anthocyanins stability of natural and copigmented barberry juice during processing and storage. Addition of copigments significantly induced the hyperchromic effect and increased the total phenolic and antioxidant activity of barberry juice. Copigmentation especially at 1:2 M ratio, markedly enhanced the color and anthocyanin stability of barberry juice during processing. Thermal treatment negatively affected the phytochemical compounds, whereas thermosonication especially at low amplitude showed no significant changes. A similar trend in the degradation of anthocyanins and color instability of samples was observed during storage. Copigmentation, especially with licorice extract, considerably increased the half-life of anthocyanins and well preserved pelargonidin 3-glucoside and the color parameters of the juice during storage. The results indicate that licorice extract can be a good alternative to synthetic copigments and the application of thermosonication maintains the effectiveness of copigmentation reaction. Industrial relevance: Barberry (Berberis vulgaris) is one of the most important medicinal plants which is mainly cultivated in Iran. Barberry fruits are used in preparing sauces, jellies, candies, marmalades and especially juice drinks. Like other berry fruits, barberry contains high amounts of anthocyanins. Due to the highly instability of these pigments, the preservation of these nutrients during industrial processing and storage of barberry juice is very important. Intermolecular copigmentation of anthocyanins with phenolic compounds, especially with phenolic extract from various plant species, is an efficient method to stabilize these compounds. Moreover, because of the adverse effect of thermal treatment on the copigmentation reaction and the degradation of nutritive compounds of fruit juice, there is a need for non-thermal processing techniques like sonication or high pressure to preserve the nutritional and sensory properties of juices. Therefore, in this study, for the first time, the simultaneous use of thermosonication and copigmentation with ferulic acid and licorice extract on the stability of color and anthocyanins of barberry juice was evaluated. The results of our study revealed that licorice extract due to having various flavonoid compounds such as liquiritin and isoliquiritin can be a good alternative to synthetic copigments. Furthermore, the application of thermosonication in comparison with thermal treatment maintains the effectiveness of copigmentation reaction.