Optimization of conjugated linoleic acid production by Bifidobacterium animalis subsp. Lactis and its application in fermented milk

Response surface methodology was used to optimize the concentration of fructooligosaccharide (FOS), sonication time and salt concentration for maximizing the production of conjugated linoleic acid (CLA) by Bifidobacterium animalis. The highest CLA was obtained under the optimized conditions including FOS (22.43%), salt (0.136%) and ultrasound time (1.47 min). The validity of the statistical model was confirmed by investigation of CLA and comparing the results by predicted value. Cell enumeration, lactose content and viscosity of optimum sample and controls were also determined. The count of cells in sonicated samples was the lowest (8.6 1og10 CFU g(-1)) and the mean amount of lactose during the fermentation time decreased in all samples, but this decrease was more significant in the optimized sample (20 g L-1). The viscosity of all samples increased with increasing the fermentation time, but this was significantly higher in the optimum sample (136 cp). According to the sensory evaluation, the optimum sample got the highest scores for appearance, mouthfeel and taste. The results confirmed the possibility of using the product as a functional food.