Development Of Jujube Dietary Fiber Yogurt

In this study, based on the traditional yogurt theory and processing equipment,skimmed milk powder, jujube dietary fiber, xylitol were prepared as raw material, and inoculated with Lactobacillus bulgaricus and Streptococcus thermophilus, to develop a new solidified jujube dietary fiber yogurt through the optimization of formula studied, and related indicators of product changes during storage were researched. The main contents and results included the following:(1) By single factor experiment, the amount of raw material, inoculum size effect on the quality of jujube dietary fiber yogurt was studied, and the most appropriate conditions for fermentation formula was established. The optimal conditions was that: 12% skimmed milk powder, 1.5% jujube dietary fiber, 6% xylitol, 1:1 proportion of the St and Lb, 4%lactic acid bacteria. Under such conditions fermentation, jujube dietary fiber yogurt senses better quality, higher total number of lactic acid bacteria.(2) Based on single factor experiment, according to the principles of central composite(Box-Benhnken) experimental, with viscosity as response, by four factors and three levels response surface analysis, the optimum formula for jujube dietary fiber yogurt(DFY)obtained as follow: 1.53% jujube dietary fiber, 7.04% xylitol, 12.53% skimmed milk powder, 3.96% lactic acid bacteria.(3) By low temperature storage experiments, the effect of jujube dietary fiber on titratable acidity, p H, total lactic acid bacteria, water holding capacity, viscosity, molds,yeasts and sensory quality of quantity during storage at 4 ? were studied. The results showed that: jujube dietary fiber have a positive effect on cryopreservation yogurt. During storage, the titratable acidity of DFY increased, p H decreased. The titratable acidity of DFY increased 13.64%, p H decreased by 6.29%, ordinary skimmed yogurt(SY) of titratable acidity increased 24.08%, p H decreased by 8.60%. The amount of lactic acid bacteria showed an overall downward trend. The lactic acid bacteria of DFY and SY decreased by 13.94%, 20.23% respectively. The water holding capacity of DFY showed rising at first, then downward trend. The viscosity of yogurt first declined slowly, then declined rapidly remain stable during the 15 d-20 d. The viscosity of DFY and SY decreased by 27.37%, 35.44%, respectively. Until the end of storage period(25 d), the mold and yeast in the yogurt has not been detected. the yogurt showed better healthproperties. During the low temperature storage experiments, DFY had a small amount of whey separation, stable structure, the color of DFY changed from red to yellowish, tasted slightly sour, continued to maintain this product unique flavor milk and jujube flavor.Compared with SY, addition of jujube dietary fiber can delay the post-acidification of yogurt, reduce the whey precipitation, increase the viscosity of yogurt and water holding capacity, slow down the viscosity and the amount of lactic acid bacteria of yogurt decline,have some help for extended shelf-life.(4) The content of three kinds of short chain fatty acids(acetic acid, propionic acid,butyric acid) before and after the fermentation of dietary fiber yogurt and ordinary skimmed yogurt was analyzed by the method of gas chromatography. The results showed that: compared with unleavened skimmed milk mixture, fermentation could significantly increase the content of the three short chain fatty acids(P<0.05). The acid increased from22.8 mg/kg to 58.10 mg/kg, an increase of 154.8%; propionic acid increased from 1.13 mg/ kg to 4.27 mg/kg, an increase of 277.9%, butyric acid increased from 3.04 mg / kg to10.34 mg / kg, an increase of 240.1%. Compared with SY, addition of jujube dietary fiber could significantly increase the content of the three short chain fatty acids(P<0.05). The acid increased from 44.42 mg/kg to 58.10 mg/kg, an increase of 30.80%; propionic acid increased from 2.29 mg / kg to 4.27 mg/kg, an increase of 86.46%, butyric acid increased from 5.49 mg/kg to 10.34 mg/kg, an increase of 88.34%.(5) Mice were randomly divided into 4 groups including control group and jujube dietary fiber groups at the low, middle and high doses. The dosage of jujube dietary fiber yogurt were 10 m L/(kg·bw), 20 m L/(kg·bw) and 3 m L/(kg·bw) respectively. The jujube dietary fiber yogurt was given for consecutive 14 days, while the control group mice were given same volume of distilled water. The effect of jujube diet yogurt on Bifidobacteria,Lactobacillus, Enterobacter, Enterococcus and C.perfringens in the fresh feces was researched. And short chain fatty acids in the colonic digesta were researched by gas chromatography to studied the effect on intestinal flora of jujube dietary fiber yogurt on intestinal flora. The results showed that: jujube dietary yogurt can reduce contents of Enterobacteriaceae, Enterococci and C.perfringens(P<0.05), promote the proliferation of Bifidobacterium and Lactobacillus(P < 0.05) and increase the content of acetic acid,propionic acid, butyric acid and total short chain fatty acids in the colonic digest(P<0.05)at the administration of 20 m L /(kg·bw). After 14 days, compared with the control group,the contents of Lactobacillus in low, middle and high dose groups were increased by 1.02%,2.42% and 3.32%, while Clostridium perfringens were reduced 16.59%, 18.78% and37.34%. Compared with the control group, the contents of bifidobacteria in middle and high dose groups increased by 4.17%, 6.41%, Enterobacter were reduced by 11.22%,14.80%, and Enterococci were reduced by 6.71%, 17.60%. Compared with the control group, in middle and high dose groups, the contents of total short-chain fatty acids in thecolonic digest were increased by 12.13%, 10.48%, acetic acid content were increased by10.36%, 8.67%,acid content were increased by 36.13%, 37.20%, and acid content were increased by 18.30%, 14.85%.Conclusion: By single factor experiment and response surface methodology, the formula was optimized and produced a fiber yoghurt with the characteristics of low-fat,sugar-free and high dietary fiber. Addition of jujube dietary fiber could have some help for extended shelf-life and increase the content of short chain fatty acids. Animal tests showed that the jujube dietary fiber yogurt can improve the intestinal flora.