温度对酸乳中乳酸菌胞外多糖作用机制的研究

Effect mechanism of fermentation temperature on the characteristicsof bacteria exopolysaccharides in yogurt

重点探讨了不同发酵温度下酸乳发酵产生的胞外多糖含量变化以及添加不同来源的胞外多糖对酸乳流变学特性的作用,结果表明:37℃条件下发酵所得酸乳多糖含量最高,达到461.4mg/mL,43℃条件下酸乳多糖含量最低,仅为247.6mg/mL。酸乳产生的内源性胞外多糖表现在产品特性上,其表观黏度及剪切应力随时间的变化都明显(P<0.05)高于外源添加胞外多糖的酸乳。表观黏度随剪切时间的变化曲线符合对数函数y=kLn(x)+b(内、外源R2分别为0.9527、0.9015)的变化规律。此外,酸乳经过发酵产生内源性胞外多糖后,其持水力(WHC)较添加外源性胞外多糖的酸乳高出26%,胶体脱水收缩作用敏感性(STS)较添加外源性胞外多糖的酸乳低46%。这说明低温有利于乳酸菌胞外多糖形成,且内源性胞外多糖酸乳的表观黏度大、持水力高。

The changes of extracellular polysaccharides content at the different fermentation temperature of yoghurt and the effects of different sources of extracellular polysaccharides on the rheology properties of yogurt were studied.The result showed：the content of exopolysaccharides was highest（247.6mg/mL）in yogurt fermented at 37℃,whereas,it was the lowest,only 247.6mg/mL,at 43℃.The apparent viscosity and shear stress of samples changing against time were obviously（P0.05）higher than that of adding exogenous exopolysaccharide.The regression curves of apparent viscosity against shear time were found to conform to a logarithmic function,y=kLn（x）＋b.In addition,water holding capacity（WHC）of yogurt with endogenous exopolysaccharide was 26% higher than that of adding exogenous exopolysaccharide.Susceptibility to syneresis（STS）of yogurt with endogenous exopolysaccharide was 46% lower than adding exogenous exopolysaccharide.It showed temperature was favorable for lactic acid bacteria exopolysaccharides formation,and the yoghurt with endogenous extracellular polysaccharide showed a higher viscosity and water holding capacity.