Study on optimization of fermentation parameters for fermented milk of Euryale Ferox Salisb

Basing on processing technic of fermented milk of Euryale ferox Salisb, four parameters including inoculation concentration, fermentation time, fermentation temperature and addition of citric acid selected by single factor investigations were used to achieve the maximum of lactic acid bacteria concentration by response surface methodology. The interaction of the respective variables and their influence on lactic acid bacteria concentration were studied by response surface analysis methodology , the simulated quadratic polynomial regression equation of prediction model was set up. The optimum fermentation parameters were determined as follows:inoculation concentration 3.3%, fermentation time 7.4h, fermentation temperature 40.5℃, addition of citric acid 0.16%, the average lactic acid bacteria concentration was 1.923×109cfu/mL, compared to the theoretical value (1.920×109cfu/mL) , the relative error was 1.56%. The regression equation will have certain guiding significance.