Background and Objectives: The use of prebiotic compounds to stimulate growth of probiotics in dairy products has been important subject in recent years. The purpose of this study was to investigate the effects of oat and rice bran on Lactobacillus acidophilus survivability and increase nutritional value of low-fat yogurt.

Materials and Methods: In this study, different amounts of oat and rice bran (0.3, 0.6, 0.9, 1.2%) were added to low-fat milk and after pasteurization, commercial yogurt culture starter within 1% concentration of 2 McFarland turbidity of Lactobacillus acidophilus was added. After incubation, the number of Lactobacillus acidophilus were counted on MRS-Bile agar. Sensory assessment of the treatment was done by five-point Hedonic scale method.

Results: The results showed that in 1.2 % of oat bran and rice bran concentration, number of Lactobacillus acidophilus were 7.7 log and 7.57 log respectively in day 0 of storage. Whereas, in the control group, 7.2 log and 7.25 log were observed, respectively. Also during the storage period, decreasing in the number of Lactobacillus acidophilus was significantly lower than control group (P≤0.05). So in the 28^th day of storage, the number of bacteria in all treatments containing oat and rice bran were higher than 10⁷cfu/gr but in the control group, its number was lower than this amount. The increase of oat and rice bran concentration lead to significant decrease in the taste and flavor scores of final product (P< 0.05) . Rice bran had worse influence on the sensory attribute than oat bran.

Conclusion: It was observed that oat and rice bran have prebiotic effects on Lactobacillus acidophilus in low-fat yogurt and could be added to this functional product in order to improve survivability of Lactobacillus acidophilus during the storage time.

Keywords: Oat bran, Rice bran, Prebiotic, Lactobacillus acidophilus, Low-fat yogurt