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

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.