Enrichment culture of Lactobacillus plantarum and preparation of concentrated freeze-dried starter

Concentrated freeze-dried starter plays an important role in development and application of fermented meat products.The Lactobacillus plantarum was chosen to be the target strain.Firstly,orthogonal experimental design was used to explore the effects of different growth factors on strain proliferation and got optimal conditions.Sceondly, the effect of centrifuge conditions on loss rate and survival rate of the strains were studied.Lastly,the effect of freezedrying conditions and different cryoprotectants on concentrated lyophilized fermented starter products were studied.The results showed that the enrichment medium of the strain was given below: carrotjuice 8%,tomato juice8%,CaCO 3 0.75% were added to MRS medium and the cell density could reach 2.682 × 109CFU/mL.The optimal centrifuge conditions were 4 000r/min for 10min,the rate of the strains yields reached 96.87%.The optimal freeze-drying conditions were the concentration of skim milk used as suspended matrix 10% and freeze-dried thickness was 0.5cm; The optimal cryoprotectant were trehalos 10%,maltose 12%,sodium glutamate 8%,and the survival rate of the freezedried starter reached 75.43%.When the bacteria freeze-drying time reached 36h,its moisture content was fit for storage requirements( 1.5% ~ 3.0%).