Survival of lactobacillus acidophilus and bifidobacterium lactis in free and microencapsulated forms in Doogh (yoghurt drink)

The present study was targeted toward the investigation of the survival of probiotic strains, namely Lactobacillus acidophilus (LAFTI-L10) and Bifidobacterium lactis (LAFTI-B94), in both microencapsulated and free forms and their effects on physicochemical and sensory properties, stability, and microstructures of Doogh during storage for 45 days in a cold room at a temperature of 5±1°C. The statistical analysis of the results showed that the number of L. acidophilus and B. lactis in free forms decreased about 1.1 and 2.2 log cycles, respectively. However, the number of the microencapsulated forms remained relatively constant during the storage period. Both free and microencapsulated forms were successful in keeping the counts of L. acidophilus and B. lactis in Doogh high enough for the therapeutic minimum (106-107 cfu/g) after 45 days. Nonetheless, the number of microencapsulated probiotics was higher than that of the free cells (P<0.05). The acidity, pH, and stability were significantly different between the samples (P<0.01). The microstructure of the samples was affected by the microencapsulation of bacteria because the sample distribution of the clusters and particles was more regular in the samples containing microencapsulated probiotics than in those containing free forms. According to the results of sensory evaluations, probiotics not only exerted no adverse effects on the physicochemical and sensory properties of Doogh but also improved the stability, microstructure, and flavor of this drink. Therefore, Doogh can be considered an effective food carrier for the delivery of probiotic organisms.