嗜热链球菌真空冷冻干燥前后发酵活力变化

Variations in fermentative activity of Streptococcus thermophilus before and after lyophilization

研究了冷冻干燥过程中不同保护剂对嗜热链球菌存活的影响,试验了嗜热链球菌冷冻干燥前后发酵活力的变化。结果表明,不同保护剂对细胞冻干存活率和冻干发酵剂活菌含量均产生显著影响(P<0.01);复合保护剂Ⅱ为最优保护剂,可使试验菌株的冻干存活率和冻干发酵剂活菌含量分别高达97.27%和3.22×1010g-1;采用复合保护剂Ⅱ制成的试验菌株冻干发酵剂在乳中42℃发酵12h的细胞生长曲线、产酸曲线和pH值下降曲线与冻干前对照发酵剂相比,均无明显变化。结果表明,利用最适保护剂制备的冻干发酵剂可以直接作为生产发酵剂使用。

Effects of different protectors on the survival of S.thermophilus ST-2 during lyophilization were studied.Furthermore,variations in fermentative activity of S.thermophilus ST-2 around lyophilization were examined.The results indicated that different protectors exerted significantly effects on the cells freeze dried survival rate and the viable cells number of freeze dried starter (P < 0 01).Compound protectorⅡ was the favorable protective additive for the cells survival during lyophilization,for instance,it could make the cells freeze dried survival rate reach 97 27% and the viable cells number of freeze dried starter reach 3 22×1010 g-1.To study the effects of starter lyophilization,freeze dried starter obtained by compound protectorⅡ,fermented in milk medium for 12 hours at 42 ℃,did not vary obviously in the curves of cells growth,produced acidit and reduced pH.The experiments showed that freeze dried starter obtained by the optimm protectors could use as direct vat inoculation starter.