Multi-frequency power thermosonication treatments of clear strawberry juice: Impact on color, bioactive compounds, flavor volatiles, microbial and polyphenol oxidase inactivation

Strawberry juice is popular among consumers for its bright color, unique flavor and rich nutrition. The aim of this study was to explore the suitable multi-frequency power thermosonication (TS) treatments to meet the requirements of microbiological safety for strawberry juice while maximizing the preservation of its quality properties. The TS treatments included 60 °C /5 min and 55 °C /15 min under dual-frequency concentrated ultrasound (DCU) and 60 °C /15 min and 55 °C /20 min under sweep-frequency divergent ultrasound (SDU). The results showed that all treatments could meet the requirements of commercial sterility (at 90 °C for 1 min). Compared with thermal processing (TP) at 90 °C for 1 min, TS treatment significantly improved the color properties of strawberry juice. SDU-60 °C and SDU-55 °C greatly retained the active ingredients in the strawberry juice. TS treatments had a stronger ability to maintain the aroma compared to TP. Especially, SDU-60 °C was the best treatment at retaining quality properties of strawberry juice with the highest comprehensive sensory evaluation score (7.68). Therefore, the results can provide scientific basis for industrial production of strawberry juice. In the current study, results showed that TS maximized the overall quality of strawberry juice while achieving the effect of sterilization and enzyme inactivation. Among them, SDU-60 °C was the best treatment method to maintain the quality characteristics of strawberry juice, which can effectively reduce the loss of approximately 70% of total phenolic content. Thus, it provides the theoretical basis and technical support for the industrial production of strawberry juice.