Studies On Improving The Content Of CLA In Fermented Milk

Conjugated linoleic acid (CLA) is a mixture comprising a series of conjugated double bond positional isomers. Since the middle of last century when it was discovered, it was reported that conjugated linoleic acid could clean free radical, enhance the antioxidant capacity and immunity, stimulate growth and development, regulate blood cholesterol and triglyceride levels, prevent atherosclerosis, promote oxygenolysis of fat and synthesis of protein and other healthy adjustment. For this study, based on Lactobacillus delbrueckii subsp. Bulgaricus, the compound mutagenesis of ultraviolet (UV) and diethyl sulfate (DES) was done and the culture medium and fermenting conditions were optimized.After that, we studied the conditions of the mutation, got in this study, in the use of yoghurt fermentation, and the main results are as follows:1,The genus Lactobacillus delbrueckii subsp. Bulgaricus1.1480 was treated by UV and DES, a mutation, higher in conjugated linoleic acid synthetic amount than the wild strain, was obtained called LD3-2. The synthetic amount of conjugated linoleic acid was 39.27μg/mL, which was 22.15% higher in productive rate.2,The culture medium and fermenting conditions for LD3-2 were optimized as: peptone 1.8%, beef extract 1.8%, yeast extract 0.9%, glucose 3%. Under the conditions of 37℃, static culturing, lower than 0.5g/L of sunflower seed oil, the synthetic amount of CLA was growing, with the increasing of sunflower seed oil. However, when the concentration of sunflower seed oil was higher than 0.5g/L the synthetic ability of CLA was inhibited by sunflower seed oil. At the concentration of 0.5g/L, the synthetic amount of CLA was as high as 50.31μg/mL, conversion rate 16.77%.3,LD3-2 was used in yoghourt fermentation, which increased the concentration of CLA in yoghourt. When glucose was used as carbon source and 0.3g/l sunflower seed oil added, the synthetic amount of CLA reached up to 49.84μg/mL. The experiment showed that the concentration of CLA was basicly stable during the shelf life of yoghourt.