Preparation process and antioxidant activity of walnut fermented drinks.

As by-products during the processing of walnut oil, walnut residues are rich in proteins, fats, vitamins and other nutrients. In the present study, the optimal preparation process of walnut lactobacillus fermented drinks was determined by pretreatment of walnut residues, strain domestication, stability studies and optimization of the fermentation process. Moreover, the antioxidant activity was measured by in vitro assays. The results indicated that the suitable solid-liquid ratio was 1:10, beating temperature was 80 c , and the addition amount of sucrose ester was 0.3%; after domesticated by the gradual domestication method, the generated acid quantity and the viable count of lactobacillus increased by 50% and 17 times more than before domesticated, respectively; a high stability of walnut fermented drinks was observed under the sterilization condition of 115 c and 15 min; compared with sodium carboxyl methyl cellulose and carrageenan, sucrose ester had an obvious stabilization effect and the suitable addition amount was 0.3%; the optimal fermentation parameters were determined as inoculated quantity of 3%, fermenting temperature of 37 c , fermenting time of 10 hrs, and sucrose addition amount of 5%. The DPPH·scavenging rate, OH· scavenging rate and total antioxidant ability of the walnut lactobacillus fermented drinks were equivalent to those of (0.463 ±0.015), (6.2 ±0.7) mg/ mL ascorbic acid solution respectively, suggesting a potential healthcare use and application value in the market development