AMELIORATION OF PHYSICO-CHEMICAL FEATURES AND ANTIBACTERIAL ACTIVITY OF BALADY YOGHURT USING PECTIN

This study was designed to evaluate the antibacterial effect of pectin against Enteropathogenic Echerichia coli (EPEC) and Listeria monocytogenes (L. monocytogenes) in Balady yoghurt as a food model. Sensory properties including taste, odor, color and texture were evaluated. Syneresis, viscosity, adhesiveness and cohesiveness were applied as rheological evaluation. In addition, physico-chemical properties such as pH value, titratable acidity, moisture and total solids were measured. Pectin incorporated in yoghurt significantly reduced EPEC and L. monocytogenes populations. Pectin at the concentration of 0.6% and 1.2% was accompanied by a significant decrease in the average count of EPEC with a reduction in percentage varied from 94.2 to 97.7% and 97.3 to 99.3%, respectively, during the last four days of the experiment. Against L. monocytogenes, pectin was bactericidal at a concentration of 1.2% on the 4th day of the experiment. Moreover, pectin at the rate of 0.6% and 1.2% significantly improved color, odor and texture of the yoghurt, while the taste was significantly improved at the concentration 0.6%. The best overall acceptability (OAA) of yoghurt was obtained at 0.6% pectin, according to the panelist review. Pectin was found to a significant decrease in syneresis; and increase viscosity, adhesiveness and cohesiveness of the yoghurt. On the physico-chemical properties, pectin did not affect pH and titratable acidity; while it decreased the moisture and increased total solids of the yoghurt. In conclusion, our present study shows that pectin has the potential to control EPEC and L. monocytogenes in Balady yoghurt with beneficial effects on its sensorial, rheological and physico-chemical properties.