Influence of different sterilization treatments on the color and anthocyanin contents of mulberry juice during refrigerated storage

The color stability of mulberry juice is affected during its processing and storage. This study investigates changes in the color of mulberry juice processed by four different sterilization treatments during 30 days of storage at 4 °C: high pressure processing (HPP at 400 MPa/5 min, 400 MPa/10 min, 500 MPa/5 min, and 500 MPa/10 min), thermal processing (TP at 70 °C/10 min, and 75 °C/10 min), high temperature short time (HTST), and membrane filtration (MF). After 30 days of storage, the retention rates of total anthocyanin, cyanidin-3-glucoside and cyanidin-3-rutinoside in juice samples treated by different sterilization methods were found to be significantly higher than those of the control group. Among these treatments, the retention rates of total anthocyanin, cyanidin-3-glucoside and cyanidin-3-rutinoside were highest in HPP (400 MPa/5 min) at 84.70%, 80.20% and 98.61%, respectively. Both TP (70 °C/10 min) and HTST treatments also showed significantly higher anthocyanin retention rates, at 83.19% and 84.27%, respectively. These results indicate that HPP (400 MPa/5 min), TP (70 °C/10 min) and HTST treatments are most suitable for the sterilization of mulberry juice. The distinct color of mulberry juice is one of the foremost qualities that imprints on consumers' senses, but it is extremely unstable in processing and storage. However, the color protection of mulberry juice was not studied previously. In this study, the protective effects of different sterilization treatments on the color-preservation and anthocyanin contents of mulberry juice were investigated for the first time. We found that the high-pressure processing treatment (HPP, 400 MPa/5 min) had the most powerful color-preserving effect. The study is of great significance as a guide to improving the color stability of mulberry juice, thereby also improving and promoting the development of the mulberry deep processing industry.