Abstract: Lactobacillus fermentum FYa1, a strain isolated from Fuyuan pickles in Yunnan was used to make direct vat set (DVS) for pickle making. The optimal centrifugation conditions were determined as follows: speed of 3 000 r/min, time of 15 min, and temperature of 15 ℃. Under these conditions, the survival rate of FYa1 was 34.57%. By using Plackett-Burman and Box-Behnken designs, the optimal formulation for freeze-drying protectants was found to consist of trehalose 8.5 g/100 mL, sucrose 8.5 g/100 mL and sodium glutamate 2.5 g/mL. The survival rate of lyophilized bacterial powder prepared by the optimized formulation was (68.53 ± 0.09)%, and the bacterial content was (2.0 ± 0.05) × 108 CFU/g. The DVS had excellent fermentation performance and showed good resurrection ability in the fermentation process. These results provide a scientific basis for the processing and quality improvement of Yunnan traditional pickles.

Key words: pickle; direct vat set; freeze-drying protectants; Plackett-Burman design