Exopolysaccharide from <i>Lactobacillus pentosus</i> Strain H2 and Its Impact on Rheological Properties and the Sensory Evaluation of Low Fat Yoghurt and UF-Soft Cheese

In this study, a total of 46 exopolysaccarides (EPS) producers were isolated from different Egyptian fermented milk products. Among these isolates, strain H2 was characterized and identified as Lactobacillus pentosus with similarity 98% based on 16S rRNA gene sequencing and phenotypic characterization. The maximum EPS secretion and cell biomass of strain H2 were 2.22 and 2.64 (g/L) at 30oC after 72 and 96 h, respectively. Among eight sugars tested for EPS production, it was noticed that all industrial by-products tested were significantly increased the secretion of EPS from strain H2. The highest EPS amount was recorded for molasses and date debs permeate followed by lactose and glucose which were 4.54, 3.08, 2.86, 2.68 and 2.56 (g/l) respectively. Electrospray Ionization Mass Spectrometry (ESI MS) indicated that EPS of strain H2 was heteropolymer and consists of D-glucose, D-glucuronic acid and L-rhamnose. Different concentration of the purified EPS isolated from Lactobacillus pentosus strain H2 were applied to low fat UF-soft cheese and yoghurt. The results of these experiments indicated the purified EPS of strain H2 significantly improved the organoleptic properties including texture, flavors and mouth feel of both low fat cheese and yoghurt. Furthermore, all parameters of rheological properties of both products including firmness, cohesiveness, gumminess, chewiness, springiness were significantly improved as the purified EPS concentrations increased. The best sensory evaluation score was recorded for low fat cheese and yoghurt fortified with EPS 0.4 and 0.8% which were 94.90 and 95.60, respectively. Finally, the problems like bitterness, low viscosity, high syneresis formation and defects of consistency which are frequently encountered of fermented milk products can be solved by using purified EPS.