Abstract
Dahi and datshi are common naturally fermented milk (NFM) products of Bhutan. Population of lactic acid bacteria (LAB) in dahi (pH 3.7) and datshi (pH 5.2) was 1.4 × 107 and 3.9 × 108 cfu/ml, respectively. Based on 16S rRNA gene sequencing isolates of LAB from dahi and datshi were identified as Enterococcus faecalis, E. faecium, Lactococcus lactis subsp. lactis. LAB strains were tested for some technological properties. All LAB strains except E. faecalis CH2:17 caused coagulation of milk at both 30°C for 48 h. Only E. faecium DH4:05 strain was resistant to pH 3. No significant difference (P > 0.05) of viable counts was observed in MRS broth with and without lysozyme. All LAB strains grew well in 0.3% bile showing their ability to tolerate bile salt. None of the LAB strains showed >70% hydrophobicity. This study, being the first of its microbiological analysis of the NFM of Bhutan, has opened up to an extent of research work that gives a new insight to the products.
Highlights
Fermented milk (NFM) products are prepared by the practice of one of the oldest techniques of milk fermentation known as the ‘back-sloping’ method in which a previous batch of a fermented product is used to inoculate the new batch (Josephsen and Jespersen, 2004; Tamang et al, 2016b)
This paper is aimed to determine some technological properties of the lactic acid bacteria (LAB) isolates from two popular naturally fermented milk (NFM) products of Bhutan- dahi and datshi such as acidification and coagulation, resistance to low pH, tolerance against bile, lysozyme tolerance and hydrophobicity assay, and to isolate and identify LAB species by 16S rRNA sequencing
Isolation of LAB was performed on the classical media i.e., Lactobacillus MRS Agar media under anaerobic conditions at 30◦C incubation for 48 h
Summary
Fermented milk (NFM) products are prepared by the practice of one of the oldest techniques of milk fermentation known as the ‘back-sloping’ method in which a previous batch of a fermented product is used to inoculate the new batch (Josephsen and Jespersen, 2004; Tamang et al, 2016b). Some NFM products of Bhutan are dahi, datshi, mohi, gheu, hard-chhurpi (chugo/churkam) and hitpa. Datshi (Figure 1B) is a cottage cheese like product, which is prepared by churning dahi for 10– 15 min until a clumping product; butter (locally called gheu) is extracted. The butter is collected in another vessel and the buttermilk, locally called mohi is heated for 15–20 min for the curdling of the product, called datshi, which is made into round small balls. It is consumed as curry in main meals in Bhutan. Some NFM products of other countries were well studied such as dahi, misti dahi, shrikhand, chhu, chhurpi, philu and somar of India, Nepal, Pakistan, and Bangladesh (Tamang et al, 2000; Dewan and Tamang, 2006, 2007; Harun-ur-Rashid et al, 2007; Sarkar, 2008; Patil et al, 2010; Tamang, 2010), kurut of China (Sun et al, 2010), aaruul, airag, byasulag, chigee, tarag, and khoormog of Mongolia (Watanabe et al, 2008; Takeda et al, 2011; Oki et al, 2014), ergo of Ethiopia, lben, rayeb, zabady, and zeer of Morocco and Northern African and Middle East
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