Preparation and Preservation Application of a Yeast Active Freeze-dried Powder for Biocontrol of Peach Brown Rot

In order to study a biocontrol agent which can effectively control honey peach brown rot after harvest,a strain of Candida intermedia Y-17 was used as the object. The cryoprotectant formulation was selected and optimized by single factor test and response surface center composite design. The biocontrol effect and storage effect of the active lyophilized powder were investigated,and its fresh-keeping effects on honey peach after harvest were also studied. It was found that the combination of 5.43 g/100 mL sorbitol,12.45 g/100 mL trehalose and 13.56 g/100 mL sodium glutamate had the best protective effect,and the survival rate of yeast could reach 84.21%±0.87%. The freeze-dried powder still had high biocontrol effect,and the yeast survival rate was 34.66% after 180 days of storage at-20 ℃. Fresh-keeping experiment showed that,yeast Y-17 active lyophilized powder could effectively inhibit the rot incidence of peach during storage,and the decay index was only 6.28% when stored at 25 ℃ until the 9th day. In addition,the yeast freeze-dried powder could also reduce the loss of water and slow down the softening rate of peach during storage. After 7 days storage at 25 ℃,the content of soluble solids,vitamin C and titratable acid in peach were 10.67%,2.15 mg/100 g and 0.17%,respectively,which were higher than those in the control group. Freeze-dried powder could also effectively maintain the integrity of peel cell membrane and played a positive role in maintaining the quality of peach after harvest.