USE OF MULTIFUNCTIONAL BACTERIAL CULTURES FOR IMPROVING CHEESE QUALITY

Abstract

Ahmed Mohamed Moawed Mabrouk. Use of Multifunctional Bacterial Cultures for Improving Cheese Quality. Unpublished Ph.D. Thesis, Department of Food Science, Faculty of Agriculture, Ain Shams University, 2016. In recent years, extensive searches have been carried out on the lactic acid bacteria (LAB) for their potential use as probiotics and biopreservatives in food and dairy industries. Nowadays, probiotic bacteria play an important role in the majority of food supplementation and extended shelf life of fermented foods. Isolation and identification of LAB from fermented dairy products gained more attention allover the world. So, total of 75 strains of LAB were isolated from local fermented dairy products. These isolates were characterized morphologically, physiologically and biochemically by using analytical profile index (API) tests. Analytical profile index (API®50 CHL) system was used for biochemical identification of Lactobacillus (Isolates grown on MRS agar) , while analytical profile index (API®20 CH) strep system was used for identification of Streptococcus (Isolates grown on M17 agar). From seventy five isolated strains only eight strains were chosen as follows: Lactobacillus rhamnosus (1 strain), Lactobacillus plantarum (1strain), Lactobacillus pentosus (2 strains), Pediococcus pentosaceus (2 strains), Lactobacillus brevis (1 strain) and Lactoccocus lactis ssp. Lactis (1 strain). These selected strains were proceeded to screen them in vitro for probiotic traits (tolerance to different concentrations of bile salts, low pH resistance, growth and viability % in different concentrations of NaCl, phenotypic safety assessment and antibacterial activity against five indicator pathogenic strains (Bacillus cereus, Staphylococcus aureus, and Escherichia. coli 0157:H7, Listeria monocytogenes Type I and Pseudomonas aeruginosa). Chosen strains were also examined for some technological properties like acidifying activity, exopolysaccharides (EPSs) production, survival in different concentrations of NaCl and milk coagulation activity.