Effect of combined ultrasonic and enzymatic assisted treatment on the fermentation process of whole Lycium barbarum (goji berry) fruit

The aim of this study was to optimize the conditions for combined ultrasonication and enzymatic treatment of whole fruit Lycium barbarum. The synergistic effects of ultrasonication and enzymatic treatment on the fermentation process, bioactive compounds, and antioxidant activity were investigated. Optimal combination of sonication time, enzyme ratio (cellulase: pectinase: protease), and enzyme concentration was determined by optimization experiments to be 10 min, 1:1:1, and 0.75%, respectively. Under these conditions, the fermentation process greatly accelerated, the viable cell count of the lactic acid bacteria after fermentation for 36 h reached (5.57 ± 0.38) × 108 CFU g−1 compared with (8.63 ± 0.29) × 107 CFU g−1 for samples without pretreatment. The total phenol and flavonoid contents of Lycium barbarum with pretreatment after fermentation for 36 h increased by 10.69% and 19.62%, respectively, compared with samples without pretreatment. The highest antioxidant activities, as measured by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, hydroxyl radical scavenging assay, and superoxide anion scavenging assay, were obtained for the treated Lycium barbarum.