Increase in conjugated linoleic acid content and improvement in microbial and physicochemical properties of a novel kefir stored at refrigerated temperature using complementary probiotics and prebiotic

Abstract The present study was aimed to determine the effects of Lactobacillus acidophilus LA-5, L. paracasei 431, and Bifidobacterium lactis BB-12 with lactulose on values of conjugated linoleic acid (CLA) and microbial, physicochemical, and sensory properties of a novel kefir. Thirteen groups were evaluated on days 1, 7, and 14 at 4 oC. The interaction between probiotics and lactulose reduced pH to 4.5 in the first week and slightly decreased on day 14 (4.35). The syneresis value was decreased by increasing the lactulose dose. The interaction could not remarkably increase probiotic survival; the greatest and lowest values were 7.18 and 7.81 log CFU/mL, respectively. The greatest and the lowest lactic acid value was 2.77 and 1.47 g/100 mL, respectively, in kefirs supplemented with L. acidophilus LA-5 and L. acidophilus LA-5+ L. paracasei 431+ B. lactis BB-12. A 4-fold increase in the acetic acid value (0.592 g/100 mL) was observed in kefirs supplemented with B. lactis BB-12 along with L. acidophilus LA-5 and L. paracasei 431 (G12). It is concluded that adding 5% lactulose along with L. acidophilus LA-5+ L. paracasei 431 to kefir could valuably increase the CLA value (3.51-8.07 ppm) and give it more acceptability of flavor, odor, and syneresis.