Isolation and identification of Lactobacillus spp. and Streptococcus thermophilus towards developing probiotic Dah

Abstract

Dahi claims as popular fermented dairy food product available in the consumer world. An attempt was made herein this study to develop Dahi with the specific lactic acid bacteria (LAB) isolated from locally available Dahi. For this view, local Dahi samples were collected and specific bacteria (Lactobacillus spp. and Streptococcus thermophilus) were isolated and identified by the lab analytical process. The analyses included morphological characteristics, microscopic observation and catalase reaction etc., to select the isolated bacteria, which were confirmed by Polymerase Chain Reaction-Gel Electrophoresis method. Five Dahi samples (T1, T2, T3, T4 and T5) were prepared using the PCR identified culture. Dahi samples (T1, T2 and T3) were prepared using Lactobacillus spp., whereas T4 sample from Streptococcus thermophilus and T5 sample was prepared by a combination of Lactobacillus spp. (T3) and Streptococcus thermophilus (T4) bacteria together. Physicochemical, microbiological and sensory properties were measured out to assess the quality of the developed Dahi. The shelf life of the product was assessed by determining pH and titrable acidity of the samples measured on day 1 and 7, respectively. Numerically variable pH and acidity were observed in the different samples of Dahi. There was an increase in acidity with the progress of the storage time, but the values were in acceptable range on day 7. Data on proximate analysis revealed that the ash and protein percentage of T3 sample were significantly (P<0.05) better than those of other samples. The viable count of Dahi cultures was well above the minimum recommended amount (106 CFU/ml) in all the Dahi samples. The sensory properties namely taste, aroma and overall acceptability of Dahi prepared from Streptococcus thermophilus (T4) and Lactobacillus spp. (T3) were significantly (P<0.05) improved compared to other samples. The results suggest that the starter culture identified and utilized in this study to develop Dahi have a potential to contribute to Dahi production technology. It can be concluded that the developed Dahi in this study might be a potential dairy food item to draw the attention of the consumer demand, acceptability and consumer world for introducing a novel dairy market outlet across the globe.