| Mulberry is rich in nutrient and functional compounds, with great health promoting-function, and is in the list of “both food and medicine”published by China national Ministry of Health. Anthocyanins, polyhydroxylated alkaloids and phenolic compounds of mulberry have been proved to be good hypoglycemic functional factors. The mulberry has high carbohydrate, is limited to use in diabetes food. Therefore through microbial transformation technique to remove carbohydrates of mulberry, combined with low temperature drying technology to research low-sugar mulberry flour was the effective way to solve this problem, and had important reference value to the utilization of mulberry development function in diabetic food. This topic respectively compared the degradation effect to carbohydrate of mulberry through three kinds of fermentation processes which were respectively of Lactic acid bacteria fermentation, yeast fermentation and Lactic acid bacteria coupled with yeast fermentation, and followed the change of nutritional components and hypoglycemic functional factors in fermentation process. Comprehensive consideration the change in carbohydrate and functional factors of fermentation products, screened out the optimal fermentation process based on the principal component analysis method. According to the optimization of the process parameters, used spray freeze drying technology to prepare low-sugar mulberry flour and with other raw materials to research three compound low-sugar flour which suitable for diabetes patients, complished analysis of physicochemical index and powder characteristics of samples. The main results were as follows:(1) Mulberry pulp single fermention process optimization. Compared the comprehensive influence of lactic acid bacteria single fermentation and yeast single fermentation to carbohydrates, functional component index(anthocyanins, 1-deoxynojirimycin and viable count) Lactic acid bacteria fermentation in the process of mulberry pulp, 72 hours total viable bacteria reached the maximum value,but still had 86.49 % fructose and 66.12 % glucose had not been removed completely. Yeast fermentation process of mulberry pulp, 24 hours of total viable count had been reached the maximum value. At this time, fructose and glucose content had been removed sugar IVcompletely. Through comprehensive score screened out the optimum fermentation process was lactic acid bacteria single fermentation 96 hours. Overall, the yeast fermentation of mulberry pulp sugar utilization rate was higher, but on functional components influence was bigger, and the lactic acid bacteria fermentation of sugar utilization rate was lower but less influence on function component.(2) Study on coupling fermentation technology of mulberry pulp. Experimental results showed that under aerobic conditions, added yeast to continue fermentation 6 hours after lactic acid bacteria fermentation 96 hours can remove sugar of mulberry pulp completely. And under anaerobic conditions, added yeast to continue fermentation 60 hours after lactic acid bacteria fermentation 96 hours, fructose and glucose sugar removal rate was 95.11 % and 84.93 %, respectively. Therefor, added yeast in later period can observably improve the removal effect of sugar. Mainly determine bioactive factors of desugaring mulberry in the coupling fermentation process. According to the comprehensive score results screened out the optimal coupling fermentation was aerobic conditions coupling ferment for 102 hours. In this fermentation condition, the remove sugar rate reached 100 %, and had minimal impact on function components and bioacive components of mulberry pulp.(3) Study on processing technology of mulberry powder series products. According to mulberry fermention products in different fermentation preparation process as the research object, optimizing the process parameters of spray freeze drying, the mulberry raw powder(not ferment), yeast fermentation mulberry powder and coupling fermentation mulberry powder was prepared, and analysed the nutritional composition, hypoglycemic functional factors and the characteristics of the powder of three kinds of mulberry powder. The result showed that through low temperature environment, pure mulberry powders were obtained by spray freeze drying. Bacteria survival rate and quantities in yeast fermentation powder were the highest, had 0.58 % and 6.42 lg CFU/g, respectively. And the content of anthocyanins reduce degree was low than coupling fermentation powder, and polyphenols and DNJ content were the highest, had 6.67 g/100 g and 26.48 mg/100 g, respectively. Alpha-glucosidase inhibition rate and ORAC values of the powder after fermentation were higher than mulberry raw powder(not ferment). These results indicated that fermentation was more conducive to resist low temperature.To investigate the protective effects of different excipients to anthocyanins, probiotics, and hypoglycemic functional factors et al. of yeast fermentation mulberry flour, selected soybeans, oats and buckwheat to mix with fermentation mulberry and then through spray freeze drying to preparate three composite mulberry flours. Compared the functional ingredients and yeast survival rate of three kinds of composite desugarization mulberry powder which affected by low temperature. The results showed that the cereal was added to improve the powder yeast survival rate and total viable bacteria, which highest in soybean powder for mulberry, respectively 11.7 % and 7.05 lg CFU/g. Amino acid content, anthocyanin content, polyphenol content, DNJ content, alpha-glucosidase rejection rate and ORAC value those of soybean mulberry powder was the highest. The water activity of all mulberry fruit powders were below to 0.6, and its hygroscopicity are low, so there had a high storability. The powder capacity and angle of repose was smaller, respectively, showed that between powder particles and particle voids are loose and porous, had better mobility. Besides coupling fermentation powder, the particle size of other mulberry fruit powders were only below to 1.60 μm, indicated that those powders had fine smooth. |
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