Conjugated Linoleic Acid Production In Functional Yogurt Containing Coculture Of Lactobacillus

Conjugated linoleic acid (CLA) is a collective term for geometric and positional isomers of linoleic acid with conjugated double bonds. CLA has recently attracted much attention as a novel type of biologically beneficial functional fatty acids. CLA is reported to reduce atherosclersis, carinogenesis, boby fat, promote growth and enhance organism immunity in food. Yogurt is considered to be a natural, nutritious and health promoting food, therefore it is accepted by the masses for consumption. The CLA-rich yogurt greatly increases the added value by complementing the deficiency of CLA.The CLA-rich yogurt was prepared with the use of food-grade microorganisms like Lactobacillus acidophilus(La), Streptococcus thermophilus(St) and Lactobacillus bulgaricus(Lb). It was of great foundation in theory to product process of CLA-rich yogurt.The fermentation conditions were optimized on La and St by Response Surface Design method. The optimal conditions were that:culture temperature41℃, substrate concentration4%, inoculum size3%, incubation time17h, proportion of La and St1:1, the concentration of CLA reached the maximum biosynthesis86.27μg/mL.Fermentation kinetics curve was obtained by study of the mixed of La and St cocultivation. The mathematics models were established based on the cells growth of the mixed of La and St cocultivation and production CLA accumulation.The yogurt was prepared by added Lb before the production of CLA was used by the mixed of La and St cocultivation. The optimal conditions were that:added time of1.5%Lb6h, sucrose content5%, and sodium carboxymethylcellulose content0.10%as the stabilizer, the concentration of CLA reached the maximum biosynthesis83.73μg/mL.The product quality of CLA-rich yogurt was studied. The results showed that the number of lactic acid bacteria was above1.0109cfu/mL and CLA content was more than71.64μg/mL in14days storage period. Also physicochemical property analysis, microbial analysis and sensory properties were in line with the standard.