Effects Of Probiotics On The Edible Quality And Fatty Acids Of Fermented Goat’s Milk

The goat’s milk has rich protein, fat, lactose, mineral substance and multivitamin, whosenutrients is close to human milk, and it’s considered to be the high-quality good of the dairy.But the goaty flavor make some people don’t like to drink goat’s milk, which limits thedevelopment of goat’s milk industry. Bifidobacterium and Lactobacillus Rhamnosus act assignificant parts of the natural microflora of human intestinal tract, the viable counts andmetabolites of their fermented milk play beneficial effects on human health. Recently, thebendfits of consumption of probiotic products were proposed, such as alleviate lactoseintolerance, antioxidative activity, cholesterol-degrading effect and anti-cancer et al. In thispaper, using SaNeng goat’s milk from Northwest Agriculture and Forestry University as rawmaterial, the effect of Bifidobacterium and Lactobacillus Rhamnosus fermented on the ediblequality of goat’s milk yogurt on the basis of using traditional yogurt starter was studiedthrough single factor experiment and orthogonal experiment, the optimum fermentationcondition was evaluated by the acidity of goat’s milk yogurt, water-retaining capability,sensory score and texture properties.The fatty acids profile of different kinds of goat’s milkproducts and fresh goat’s milk were determined and compared through gas chromatography,in order to investigate the mechanism of the improvement of the goaty flavor by fermentation.The mainly obtained results were listed as the following.(1) The optimum of fermented goat’s milk with Bifidobacterium: Through single factorexperiment and orthogonal experiment, the optimum fermentation condition was evaluated.The results indicated that high edible quality goat’s milk yogurt can be obtained when sugaradding amount was7%, inoculation amount was6%, the ratio of three lactic acid bacteriawhich were Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus andBifidobacterium is1:1:2, and fermentation temperature was42℃.Through verification test,the value of titratable acidity was98°T, water-retaining capability was47.23%, sensory scorewas93, the viable count beyonds10~7cfu/mL when the optimum fermentation condition wasbe used.The goat’s milk yogurt has a good curd, pleasant mouthfeel with moderate sweet andsour, pure yogurt flavor and slight goaty flavor.(2) The optimum of fermented goat’s milk with Lactobacillus Rhamnosus: Throughsingle factor experiment and orthogonal experiment, the optimum fermentation condition was evaluated. The results indicated that high edible quality goat’s milk yogurt can be obtainedwhen sugar adding amount was7%, inoculation amount was3%, the ratio of three lactic acidbacteria which were Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilusand Lactobacillus Rhamnosus was1:1:3, and fermentation temperature was42℃. Throughverification test, the value of titratable acidity is101°T, water-retaining capability is39.89%,sensory score is95, the viable count reaches10~8~10~9cfu/mL when the optimum fermentationcondition was be used. The goat’s milk yogurt has a good curd, pleasant mouthfeel withmoderate sweet and sour, pure yogurt flavor and slight goaty flavor.(3) The study of goat’s milk flavor characteristics: Through correlation analysis betweenfatty acids profile of goat’s milk,bovine milk products and goaty flavor sensory scores, foundthat a positive correlation between C6:0、C8:0、C10:0、∑SCFA、C11:0、C12:0、C18:0、C18:2and goaty flavor, and a negative correlation between C4:0、C14:0、C15:0、∑MCFA、C16:0、C17:0、C18:1、C18:3、∑LCFA and goaty flavor. Thus it was also proved that the goatyflavor substance was short and middle-fatty acids such as C6:0、C8:0、C10:0、C11:0、C12etal.(4) Effects of Bifidobacterium and Lactobacillus Rhamnosus on the fatty acids offermented goat’s milk: Compared with fresh goat’s milk, fermented goat’s milk withBifidobacterium/Lactobacillus Rhamnosus has higher content of short and middle chain fattyacids, lower content of long chain fatty acids. Fermented goat’s milk with Lactobacillusdelbrueckii subsp. Bulgaricus and Streptococcus thermophilus (1:1) has lower content of shortand middle chain fatty acids, higher content of long chain fatty acids. Fermented goat’s milkwith the optimum fermentation condition, content of short and middle chain fatty acidsdecreased significantly, while content of long chain fatty acids increased, thus lessened thegoaty flavor. The mechanism of the improvement of the goaty flavor by fermentation wasstudied.The mainly obtained results were listed as the following: The co-operation ofBifidobacterium/Lactobacillus Rhamnosus and Lactobacillus delbrueckii subsp.Bulgaricusand Streptococcus thermophilus could degradate fatty acids of goat’s milk under cetaincondition. More short and middle chain fatty acids were transformed to long chain fatty acids,thus the goaty flavor was lessened.