Effect of sweetners (Honey) and storage periods on the organoleptic quality of yoghurt and the survival of in Yoghurt

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Seven lots of yoghurt were prepared, two lots each of plain yoghurt, strawberry yoghurt and three lots of honey yoghurt. The yoghurt packages of each type were divided into three groups, The first was subjected for organoleptic examination, the second for determination of pH and the third group was artificially contaminated with Listeria monocytogenes (L. m) Scott A at initial inoculums 2.4 * 10^7 cells / g., for study the survival of bacterium in yoghurts. All examined samples were stored at 4 – 5 C. The results of comparative organoleptic examination, quantitative detection of L. m Scott A as well as pH value of yoghurt were summarized as organoleptically the medium honey yoghurt (6% honey) was the superior (84%), while the inferior tasted samples were strawberry yoghurts (66 – 68%). Bacteriologically : L. monocytogenes Scott A was surviwed twenty twodays with a pH value 3.79 in plain yoghurt, seven days in honey yoghurt (3%honey), the final pH value was 3.86 and six days in honey yoghurt (6&9%honey), the last pH value was 4.18 – 4.21. The survival rate of bacterium in strawberry yoghurt with 3&6% sucrose is nearly similar with that recorded in honey yoghurt. In all cases the listerial count was reduced to 10^2 cells / g, then failed to be detected.

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