Optimization of Fermentation Process of Set Yogurt with Auricularia auricular Polysaccharide

Auricularia auricular polysaccharide(AAP)and pure milk were used as raw material. The mixture of Streptococcus thermophiles,Lactobacillus bulgaricus and Lactobacillus casei were selected as starter culture to investigate best fermentation process of AAP setyogurt. With sensory evaluation as the index,effects of sucrose content,AAP contents,gelatin contents,fermentation time,fermentation temperature and fermentation agent contents on sensory evaluation of AAP set yogurt were studied by single experiments. Furthermore,response surface test was used to optimize the fermentation process parameters of AAP set yoghurt,and the yoghurt quality was analyzed. The results showed that the optimal technological parameters of AAP set yoghurt were gelatin 0.33%,sucrose 7.0%,fermentation agent 3.0%,AAP 0.1%,fermentation time 6.9 h and fermentation temperature 42℃. Under this optimal process,the sensory scores of AAP set yogurt was(9.30±0.08) score in the validation experiment,which was consistent with the predicted value. Compared with the sensory scores(8.83±0.12 score),water holding capacity(63.83%±2.69%)and texture characteristics of common yoghurt,the AAP set yoghurt had higher water-holding capacity(72.14%±3.58%)and texture characteristics,which result in better sensory scores. In addition,the free amino acids and extracellular crude polysaccharides of AAP yogurt significantly increased. And the fat contents(2.35±0.25 g/100 g)of AAP yogurt was significantly lower than that of common yogurt(4.16±0.39 g/100 g). It indicated that AAP set yogurt had higher nutritional value and health care function. Therefore,AAP set yogurt had the potential to develop into a new type of functional yogurt.