Fermentation Process Of Soy Isolated Protein Hydrolysates And EPS Produce On Yoghurt

Yoghurt is a kind of fermented food contained probiotics, which usually regarded as functional food. What’s more, the stirred yoghurt is accepted by the majority of customers for its mouthful taste, protein-rich in nutrition. Yoghurt has a variety of potential function, such as enhance lactose metabolize, immune system, intestinal tract bacteria, etc. How to shorten the fermented time of yoghurt, at the same time ensure the quality of product are the most difficult technical problems, which confused lots of milk enterprises. This paper aimed at investigating the effect of SPIH on the fermented process of yoghurt and after fermented process when they stored in the refrigerator. Meanwhile, this article can provide some theoretical instruction and reference with higher quality, healthier and more nutritious fermented product.In this study, Alcalase 2.4L, Papain, Trypsin and Protamex were used to hydrate the SPI, by control different hydrate time, we chose different hydrate degree of SPI added in the raw material of milk to record its variation during fermentation to make a conclusion. The results revealed that the promotion effect of SPIH was better in accordance with the DH(6.99~24.61%) went up, the most effective products were hydrate by Alcalase2.4L and Trypsin. This mainly reflected by the fast effect of acid production, the growing numbers of Lactic acid bacterial and the shortage of fermentation time. Most importantly, SPIH of Trypsin could reach the fastest fermentation end, which shortened 21.8% time compared to the control sample. In addition, the molecule weight of SPIH also had an effect on the fermented process: the molecule weight is lower than 1k Da plays the key role.SPIH has different effect on the stirred milk during storage time. The conclusions are as follows: SPIH had a promotion effect on the number of Streptococcus bacteria and Lactobacillus bacteria, compared to the control, which was almost one ten of the added sample. SPIH of Alcalase2.4L for 24 hours could reach the highest viscosity of 4430 cp after 7 days’ storage, while SPIH by Papain for 24 hours could reach the highest viscosity of 4614 cp after 5 days’ storage. Also, the amount of SPIH had a great influence on the viscosity of yoghurt during storage. When added 0.3% of SPIH by Alcalase2.4L and Papain in the raw material milk, the viscosity could reach the highest value after 7 to 15 days’ storage, which were 4434 cp and 4814 cp respectively. In addition, those two samples obtained better texture, mouthful and taste than the control sample after 15 days’ storage.The separation approaches chose the combined enzyme and TCA method could get the most amount of crude exopolysaccharide, which owns higher exopolysaccharide and lower protein. The control sample, which used this separation method obtained the crude exopolysaccharide of 63.9% of saccharide and 18.7% of protein. The product of exopolysaccharide of yoghurt added with SPIH had an influence by the storage time. The sample added the SPIH by Alcalase2.4L could reach the highest viscosity after 15 days’ storage, the abstraction rate of exopolysaccharide was 2.47%. The result of the molecular of DEAE-Sepharose fast flow demonstrate that the addition sample have two exopolysaccharides in the chromatogram of 0M Na Cl, while the control just have one kind of EPS. The molecular of 0.1M Na Cl of the two samples were almost between 1 to 2 k Da, which can be regarded as the same EPS.