الفهرس 
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Abstract
Food processing companies and Food Technology and Preservation Laboratories are currently interested in LAB which are used as starter cultures for food fermentation.The current interest is to use LAB as starter and protective cultures for making foods and protection of the food product obtained by their ability to produce antimicrobial substances including lactic acid, diacetyl, hydrogen peroxide and bacteriocins.
Due to the current interest in using LAB as starter and protective cultures, the work in this thesis was focused to find out strains of LAB; producers of bacteriocins and possessed technological properties make them good qualifications to be used as probiotic cultures and starter strains for food fermentations with protection of the food product obtained. The probiotic capabilities of LAB are due to their ability to produce acids, degrade cholesterol precipitates, production lactase enzyme for improving lactose intolerance in lactose intolerant people and production of antimicrobial compounds to inhibit pathogenic bacteria. In addition to above properties, growth capabilities make further qualification of LAB strains to be used as starter cultures for food fermentations. Seven types of Zabady were a scope of this study all were choosen as they wereavailable in Zagazig city, Egypt. Ten samples from each Zabady type were analysedmicrobiologically and two representative isolates were picked up from each sample. Thus 20 isolates were isolated from each Zabady type and a total of about 140 isolates were obtained from seven Zabady types tested. All Zabady samples showed a bacterial count starting from 2.0×102 CFU/ml. This reflected that Zabady is a suitable medium for occurrence of LAB.