Formulation Optimization of Freeze-Drying Protectant for Probiotics Powder by Vacuum Freeze-Drying

In order to improve the survival rate of probiotics lyophilized powder,the effects of freeze-drying protectants on the survival rate of probiotics were studied using vacuum freeze-drying mothod. The protectants included skim milk powder,xylo-oligosaccharides,soluble starch and V_Csodium salt and the probiotics included Lactobacillus plantarum SC1, Bacillus coagulans XP2 and Saccharomyces cerevisiae SA1. The optimum combinations were selected by single factor and orthogonal test. With the pre-freezing temperature -70 ℃,2h,and freezing temperature -50 ℃,10 Pa,38h,the best formula combinations of protectant for L. plantarum was soluble starch 10%,V_Csodium salt 3%,skim milk powder 12%,xylo-oligosaccharide 14%;the best formula combinations of protectant for B. coagulans was xylo-oligosaccharide 8%,V_C sodium salt 4%,soluble starch 14%,skimmed milk powder 8%;the best formula combinations of protectant for S.cerevisiae was xylo-oligosaccharide 10%,V_C sodium salt 2%,skimmed milk powder 12%,soluble starch 12%. Under the optimal formula protectant,the freeze-drying survival rate of the three strains were 83.2%,83.7% and 86.7% respectively,and the number of viable bacteria were all higher than 1.0×10⁸ CFU/g,which has a good commercial application value.