Effect of exopolysaccharide producing starter culture on the characteristics of skim milk coagulum

Abstract

The present study attempted to evaluate the effect of incorporating an exopolysaccharide (EPS) producing indigenous strain of lactic acid bacteria (LAB) with a non-EPS producing industrial strain of LAB on the physico-textural properties of product. For this, characteristics of the skim milk coagulum prepared using monocultures and mixed cultures were determined and compared. EPS producing Pediococcus pentosaceus DMG01as well as the non-EPS producer Lactococcus lactis were graded as weak acid producer based on Horrall Elliker test. Ability of the isolate DMG01 to ferment citrate endorsed its flavour production potential. Colony characteristics in Congo red agar indicated the indigenous isolate to be an EPS producer and industrial stain a non-EPS producer. The treatment products were prepared using EPS negative LAB (A), EPS producing P.pentosaceus (B) and a combination of these in the ratio 1:1 (C). The titratable acidity of curd B (0.96 percent LA) and curd A (0.86 per cent LA ) was significantly less than C (1.10 per cent LA). In line with the titratable acidity, pH differed significantly between the treatments. Syneresis value of A (1.72 per cent) was significantly higher than both B (1.55 per cent) and C (1.28 per cent). Penetrometer reading was also significantly higher for A (36.25mm), indicating that the curd tension of the A was significantly lower than both B and C. Scanning electron microscopy revealed extensive fusion of casein micelles in milk coagulum prepared with EPS producing starter culture. The results underscore the advantageous effect of EPS producing starters on textural characteristics of the fermented product.