| Probiotics,as the active microorganisms that improve host’s intestinal microecology,have the functions of enhancing immunity,lowering blood lipid,regulating intestinal flora and delaying aging.Lactobacillus reuteri,as a probiotics,has been approved for use in functional food and dairy industries in China,and is closely related to human health.Yogurt,because it’s good probiotic function and rich nutrients,is an ideal carrier for the development of functional foods.Our recent research found that the crude coix slurry（solid to liquid ratio of 1:10）can significantly promote the growth of Lactobacillus reuteri,with viable cell count of up to 1013 CFU/m L.However,the fermentation of coicis yoghurt inoculated with Lactobacillus reuteri has not been reported at home and abroad.Therefore,in this study,semen coicis and fresh milk were used as the main raw materials,and Lactobacillus reuteri,Streptococcus thermophilus and/or Lactobacillus bulgaricus were used to perform cooperative fermentation of semen coicis yoghurt,respectively,to screen out the best combination of strains for fermenting semen coicis yoghurt.The process optimization and quality analysis of semen coicis yoghurt were carried out by response surface design test.Meanwhile,the animal model was used to evaluate the probiotic function of semen coicis yogurt.The main conclusions are as follows:（1）The screening results of the optimal strain combination of fermented semen coicis yoghurt showed that the highest content of organic acids was lactic acid（11.4～18.38 mg/m L）,followed by citric acid and tartaric acid.However,the masticability,cohesion and adhesiveness of the three-strain co-fermented semen coicis yoghurt（RTB-C）were significantly higher than those of the two-strain co-fermented semen coicis yoghurt（RT-C,RB-C and TB-C）（p<0.05）.The response values of sour,sweet,bitter,fresh and salty were different among different products（p<0.05）.RTB-C had the strongest sweet and umami taste,and bitter,astringent and sour taste were the weakest.RTB-C had the largest flavor substances（82 species）and the highest total content（1331.74 ng/m L）,and the contents of alcohols,acids,lipids and ketones of the three-strain fermentation sample were higher than those of the two-strain fermentation sample.Therefore,the three-strain synergistic fermentation process should be selected in the production of high-quality semen coicis yoghurt.（2）The fermentation process of semen coicis yoghurt was optimized through single factor screening and response surface analysis,and its quality was analyzed.The results showed that the optimized process paremeters of semen coicis yoghurt fermentation were:semen coicis slurry content was 27%,granulated sugar content was 7%,strain inoculation quantity was 6%,strain ratio was 0.9:1:1,fermentation temperature was 41℃and fermentation time was 8.4 h.The contents of organic acids in semen coicis yoghurt（RTB-C）,semen coicis free yoghurt（RTB）,ordinary yoghurt（TB）and commercial probiotic yoghurt（PY）were 12.45～15.50 mg/m L,and content of lactic acid was the highest.The taste response values of sour,sweet,bitter,fresh and salty were different among different yoghurts（p<0.05）,and thedifference in astringency was the largest,followed by sour,umami,salty,bitter and sweet taste.It is worth noting that of the taste response values of sour,astringency and salty in RTB-C were significantly lower than those in other yoghurts,while the taste response values of sweet and umami were significantly higher than other yoghurts（p<0.05）.The contents of total free amino acids（40.57 mg/g）and essential amino acids（14.08mg/g）in RTB-C were significantly higher than other yoghurts（p<0.05）.Among the flavored amino acids,RTB-C had the highest contents of umami and sweet amino acids.The varieties（83 speices）and contents（835.31 ng/m L）of RTB-C were significantly higher than other yoghurts.The volatile flavor substances in yoghurts were dominated by alcohols,acids and aldehydes.Therefore,the semen coicis yoghurt co-fermented with Lactobacillus reuteri has the advantages of high nutritional quality and balanced flavor.（3）Comparing the effects of RTB-C with RTB,TB and PY on blood lipid regulation and immune regulation in mice,the results showed that the contents of serum TG,TC and LDL-C of RTB-C mice were significantly lower than other groups（p<0.05）,and were decreased by 68.14%,42.24%and 60.53%compared with HFD（high fat model group）,respectively.While the level of HDL-C in RTB-C was significantly higher than that of the other groups（p<0.05）,which was 94.59%higher than that of HFD（p<0.05）.The contents of T-AOC,GSH-Px and T-SOD in liver of RTB-C mice were significantly higher than those in the model control group（p<0.05）.The serum Ig A,IL-10,LGM,Ig G and IL-12 contents in RTB-C mice were the highest,and the contents of Ig A and IL-12 in RTB-C mice were significantly higher than those of others（p<0.05）.Therefore,semen coicis yoghurt has better blood lipid regulation and immune regulation effect on mice.（4）Comparing RTB-C and RTB,TB and PY on the mouse intestinal flora regulation experiment,the results showed that the diversity and richness of mouse intestinal flora in RTB-C group were significantly higher than those in other groups（p<0.05）.Among them,The relative abundance of Bacteroidetes increases and Firmicutes decreases,and the ratio of Bacteroidetes to Firmicutes increases,which helps to improve obesity;Anti-inflammatory Clostridium and Clostridium,butyric acid-producing Rumenococcus,and short-chain fatty acid-producing Bacteroides all show high relative abundance in RTB-C.The relative abundance of Prevotella increased in all yoghurt groups,while the relative abundance of Clostridium and Desulfuriovibrio decreased in all yoghurt groups.The relative abundance of lactic acid bacteria with bacteriostasis,improving obesity and inflammation was the highest in RTB-C.It should be of concern that,the relative abundance of Lactobacillus reuteri may only increased in RTB-C due to growth-promoting effect of semen coicis.Therefore,semen coicis yoghurt has a good regulatory effect on intestinal flora of mice. |
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