Utilization of exopolysaccharide producing lactic acid bacteria for improving the quality of low fat curd

Abstract

An experiment was conducted to utilize exopolysaccharide producing lactic acid bacteria for the preparation of low fat curd. Exopolysaccharide producing cultures were isolated from 25 curd samples collected from different sources. From this samples 32 EPS producing cultures were isolated. Based on morphological, biochemical and sugar utilisation tests the isolates were grouped. According to results, two were Streptococcus thermophilus. Eight of the isolates were Lactobacillus. Remaining 22 isolates were identified as Lactococcus. All the 32 EPS producing isolates showed mucoid colonies with a slimy appearance when the isolates were streaked on MRS or M17 agar with 4 per cent sucrose which indicates the capability of EPS production. Exopolysaccharides produced by different isolates were purified by ethanol precipitation method followed by dialysis and they were quantified by phenol sulphuric acid method. The maximum EPS yield was observed in two isolates of Lactococcus lactis subsp lactis with 109 mg/L and 107.4 mg/L respectively. Low fat curd was prepared from skim milk by using these two EPS producing isolates. Physico - chemical parameters and sensory quality of the low fat curd were analysed by standard methods. Statistical analysis revealed that the whey separation and curd setting time of low fat curd decreased with the use of exopolysaccharide producing isolates. There was no significant difference in fat content but an increase in total solid content of curd samples prepared by EPS producing isolates was observed. Overall sensory scores were higher for low fat curd prepared with EPS producing isolates when compared to control curd prepared with non EPS producing cultures.