Study Of Non-dairy Probiotic Matrix Based On Enzymatic Hydrolysates Of Wheat Bran And Soybean Meal

In recent times, the development of non-dairy probiotic food has signaled an important advance in the probiotic food industry. Compared to fermented dairy products, non-dairy probiotic beverage has the advantages of no lactose intolerance and low cholesterol content. The key to the investigation of non-dairy probiotic beverage is matrix selection and substrate modification by using an enzyme mixture. This study took wheat bran as basic material, proper amount of soybean meal were added to improve the amino acid composition of the substrate, and Aspergillus oryzae were used to produce compound enzymes to decompose nutrients in wheat bran and soybean meal. Thus we can obtain a new kind of non-dairy matrix based on enzymatic hydrolysates of wheat bran and soybean meal(WB-SMEH) with low prices and rich nutrition, which can be used to produce non-dairy probiotic products with comprehensive and balanced nutrition.The results showed that A. oryzae culture could be used as a kind of compound enzyme preparation to conduct effective digestion on its own and additives, the product was rich in nutrition and suitable for the growth of lactic acid bacteria(LAB). Under the optimal conditions of enzymatic hydrolysis: temperature 55℃, solid-liquid ratio 1:10, boiled wheat bran, wheat bran/A. oryzae culture 1/5, hydrolysis time 5 h, the main nutrition content of the acquired WB-SMEH were as follow: amino nitrogen 0.20 g/100 m L, reducing sugar 2.19 g/100 m L, total sugar 2.30 g/100 m L.WB-SMEH could support the growth of various kind of LAB, and the viable count reached 108-109 cfu/m L, the average logarithmic growth was 1.851, the final p H was 3.84-3.97. After 10 h fermentation in WB-SMEH, L. Rhamnosus went into the stable phase, and the final viable count could up to 3.23×109 cfu/m L. After refrigerated 90 d under 4℃, the logarithmic viable count of L. Rhamnosus in fermented liquid decreased from 9.5 to 7.99, still meet the requirements of probiotic food.The effect of the key components in WB-SMEH on the growth of LAB was investigated. Wheat bran is rich in phytic acid. The phytic acid of WB-SMEH was removed by adding phytase to study the effect of phytic acid on LAB growth. The results showed that the phytic acid in WB-SMEH only had weak inhibitory effect on the growth of LAB. Moreover, wheat bran is rich in xylan, and its hydrolysate is rich in oligosaccharides. The influence of xylan hydrolysate of wheat bran on the growth of LAB was studied based on MRS medium, the results showed that xylan hydrolysate of wheat bran could promote the growth of LAB, and presented a certain concentration effect. The greater xylan hydrolysis degree(the smaller average molecular weight), the better LAB growth.The nutritional characteristics and functional properties of WB-SMEH were also studied. The results showed that WB-SMEH was not only rich in amino acids, peptides, oligosaccharides, vitamin B and minerals and other nutrients, but also had good functional properties. The changes of WB-SMEH functional properties before and after fermentation were compared, and the results showed that after LAB fermentation, both antioxidant activity and anti-alpha-glucosidase activity of WB-SMEH fell slightly. The half clearance of WB-SMEH on DPPH free radical increased slightly after LAB fermentation, from 0.68 mg/m L to 0.81 mg/m L. And the half inhibitory concentration of WB-SMEH on alpha-glucosidase after LAB fermentation was increased from 10.31 mg/m L to 14.09 mg/m L. By ethanol precipitation and macroporous resin adsorption separation, the results showed that phenol and small molecule amino nitrogen were main antioxidant. The effect of enzymatic hydrolysis on anti-alpha-glucosidase activity was studied by using amylase, xylanase, protease to decompose wheat bran respectively, the results showed that only the protease hydrolysis could cause sharply increase of anti-alpha-glucosidase activity of the matrix, but the effect of other enzymes were small.Peptide molecular weight distribution of WB-SMEH was studied by HPLC analysis, the results showed that proteins in wheat bran and soybean meal had been decomposed into oligopeptide and amino acid, molecular weight of WB-SMEH peptide were less than 5000 both before and after fermentation. Amino acid and oligopeptide whose molecular weight were less than 500 in WB-SMEH before and after fermentation were accounted for 89.37% and 90.39%, respectively. WB-SMEH was rich in amino acids, which was conducive to the growth of LAB. This study also compared the change of VB before and after fermentation. WB-SMEH contained VB, through LAB fermentation, the VB5 content decreased by 42.49%, but VB2 significantly increased by 566.67%, VB6 increased by 17.56%, and there was little effects on VB1. WB-SMEH contained minerals such as calcium, phosphorus, magnesium, iron, zinc, and their content were almost unchanged before and after fermentation.