Effect of cryoprotectant on low temperature lactic acid bacteria complax starter

Low temperature lactic acid bacteria,isolated from traditional fermented yak milk from qinghai-tibet plateau areas were used as the research object.The impact of four kinds of cryoprotectants on the survival rate of lactic acid bacteria complax starter during storage was assessed.Based on the results,orthogonal experiment was adopted to optimize cryoprotectant composition.The results showed that the optimum cryoprotectant composition was glycerol 8m L/L,sucrose 10%( w/v),skimmed milk 15%( w/v). The rank of protection effect on the viable counts was skimmed milk > glycerol > sucrose,and the freeze-dried survival rate was 90.55%. Compared with commercial starter culture,low temperature starter fermented yogurt had better texture,and the acidity was 92° T.The sensory evaluation value was 95 points,and the viable counts( 10.3lg CFU/m L) significantly higher than commercial starter culture fermented yogurt( p < 0.01).