Effect of Inoculation Level of Lactobacillus rhamnosus and Yogurt Cultures on Conjugated Linoleic Acid Content and Quality Attributes of Fermented Milk Products

ABSTRACT:  The effect of inoculation concentration of Lactobacillus rhamnosus and yogurt cultures and storage time on conjugated linoleic acid (CLA) content and quality attributes of fermented milk products was determined. Yogurt culture ( Lactobacillus bulgaricus and Streptococcus thermophilus, 1:1 ratio, YC ) , L. rhamnosus (LB), and LB co-cultured with yogurt culture, were inoculated at 10⁶, 10⁷, 10⁸ CFU/mL into a milk with hydrolyzed soy oil as the lipid source. CLA content, microbial counts, acidity, texture, and volatile flavor profile of the fermented milk products were stable during storage at 4 °C for 14 d. Total CLA contents ranged from 0.51 to 1.00 mg CLA/g lipid following 14 d of storage. Inoculation level of L. rhamnosus and yogurt cultures had no significant effect on CLA content and texture, but affected acidity and the volatile flavor profile of the fermented milk products. The fermented milk products produced by L. rhamnosus co-cultured with yogurt culture with 10⁷ CFU/mL total inoculation level resulted in a high CLA content and desirable quality characteristics. This research demonstrated that the optimal inoculation concentration and the combination of L. rhamnosus and yogurt cultures were important factors to produce fermented milk products with CLA content and acceptable quality attributes.