| Sanghuangporus is a traditional medicinal fungus with immunity enhancing,blood lipid lowering,free radical scavenging,anti-aging,anti-virus and antitumor effects.Yogurt is a kind of nutrient-rich probiotic fermented dairy products,which is increasingly valued by people for its unique nutritional value and health care function.Functional health yogurt is the future development direction of dairy drinks and has a large market potential.Sanghuangporus lonicericola,a sort of Sanghuangporus,is a newly identified strain in recent years,containing triterpenes,flavonoids and other functional components,and has a large potential for development.In this study,we isolated and identified lactic acid bacteria from the samples collected from Nanshan pasture,and used the identified lactic acid bacteria strains combined with the medicinal fungus S.lonicericola to carry out functional yogurt fermentation research on S.lonicericola.The main research contents and results are as follows:1.Three suspected lactic acid bacteria were isolated from soil samples collected from Nanshan Pasture and named NS1,NS2 and NS3,respectively,and their species identification was performed by morphological observation and 16S rRNA sequence analysis.The results showed that these three strains were Lactobacillus delbrueckii subsp.lactis,Streptococcus thermophilus,and Lactobacillus delbrueckii subsp.bulgaricus,of which NSl and NS3 belong to the genus Lactobacillus and NS2 to the genus Streptococcus.2.The three isolated strains were used as fermenting strains to carry out yogurt fermentation research and explore the fermentation pattern of functional yogurt with the addition of S.lonicericola fermentation broth.The optimal fermentation process of S.lonicericola yogurt was determined by single-factor experiment as follows:the inoculation ratio of inoculum of L.delbrueckii subsp.lactis,S.thermophilus and L.delbrueckii subsp.bulgaricus was 1:1.5:1,the total inoculum was 3%,the addition of S.lonicericola fermentation broth was 15%,the fermentation temperature of yogurt was 42℃,and the fermentation time of yogurt was 5 h.The S.lonicericola yogurt obtained under these fermentation conditions has a high viable lactic acid bacteria and sensory quality,and also has the active substances triterpenes and polysaccharides.The results further investigated the quality changes of S.lonicericola yogurt during storage under different fermentation conditions,and some physicochemical indexes(acidity,water holding capacity,protein content and butanedione content)and microbial indexes(total number of viable lactic acid bacteria)of the yogurt were used as the in investigation indicators,and the results further verified that the fermentation conditions of S.lonicericola yogurt were 15%fermentation broth,yogurt fermentation temperature of 42℃,yogurt fermentation time of 5 h,and it was determined that the storage time should not exceed 7 days.3.The results showed that the total number of viable lactic acid bacteria and the protein content of the yogurt were 36.34×10~6 CFU/mL and 23.87 mg/mL,respectively,which were higher than those of the control yogurt(17.52×10~6 CFU/mL and 19.43 mg/mL)without the addition of S.lonicericola;Meanwhile,the typical flavor substance butanedione content of S.lonicericola yogurt was 8.57 μg/mL higher than that of the control yogurt(5.21 μg/mL),and the polysaccharide content was 31.47 mg/mL higher than that of the control yogurt(1.89 mg/mL),respectively.In addition,the content of triterpene compounds,a unique substance detected in S.lonicericola yogurt,reached 15.39 mg/mL.Compared to the control yogurt with 92.69°T acidity and 53.64%water retention,the acidity and water retention of Lonicera japonica yogurt decreased to 89.46°T and 47.23%,respectively.The sensory score of the developed yogurt product was 86.The yogurt has uniform color,light creamy yellow color,uniform tissue state,slight whey precipitation,delicate taste,both yogurt aroma and slight mushroom aroma of S.lonicericola.The results of GC-MS analysis of volatile products in the samples showed that 119 and 124 metabolites were detected in S.lonicericola yogurt and control,respectively,and 80 metabolites were detected in S.lonicericola fermentation broth.Among them,the metabolites of S.lonicericola yogurt were 3Hydroxypropionic acid,Erythrose,4-Acetamidobutyric acid,Ribonic acid,gamma-lactone,salicin,among which salicin has anti-inflammatory and cell aging inhibitory effects,indicating that S.lonicericola yogurt may also have this property.In addition,some amino acids,citric acid and succinic acid,which contribute to the production of yogurt flavor compounds in S.lonicericola yogurt,were expressed at a higher level compared with the control In addition,some of the amino acids,citric acid and succinic acid that contribute to the production of flavor compounds in S.lonicericola yogurt were expressed at higher levels compared to the control yogurt,indicating that the addition of S.lonicericola fermentation broth resulted in improved flavor and anti-inflammatory properties.The presence of these metabolites suggests that the yogurt produced in this study has a better flavor and may have anti-inflammatory and cellular aging inhibiting properties.In this thesis,the lactic acid bacteria from soil samples of Nanshan pasture were isolated and identified,and the optimal mode of fermentation of S.lonicericola yogurt was investigated.The results showed that S.lonicericola yogurt is rich in S.lonicericola triterpene polysaccharide active ingredients and unique compounds such as salicin,and has the potential to be developed into a health functional yogurt. |
