| Abstract: |
One hundred random samples of raw milk ( 50 samples) , pasteurized milkand sterilized milk ( 25 samples of each) were collected from different localities inSharkia Govemorate to determine the incidence of psychrotrophic bacteria, using standard plate count agar.All samples of raw milk showed strong positive Guaiac test result andthus proved to be raw. While phosphatase enzyme could not be detected in allexamined pasteurized milk samples. While all samples of sterilized showed no turbidity and thus proved to be efficient sterilized milk.The results of keeping quality tests revealed that 6 % of raw milk sampleswere precipitated with alcohol, while 2 samples were clotted on boiling.The mean acidity percent in raw, pasteurized and sterilized milk were0.15 ± 0.004, 0.14 ± 0.003 and 0.14 ± 0.002 , respectively.The bacteriological examination showed that the mean psychrotrophiccount / ml. in raw, pasteurized and sterilized milk samples were 3.20 x 106 ± 1.20 x 106, 1.04 x 104 ± 0.32 x 104 and 1.83 x 102 ± 0.61 x 102 ,respectively.Pseudomonas spp. , Enterobacteriaceae spp, , Staphylococcus spp, Bacillusspp. , Acinetobacter spp., Alcaligenes spp. , Aeromonas spp. , Vibrio spp. ,Flavobacterium spp., Micrococcus spp. and Achromobacter spp. could beisolated from raw milk samples with varying percentages ranged from 2 % to 46 % . All psychrotrophic isolates from raw milk were tested for proteolytic and lipolytic activities and revealed varying percentages.Pseudomonas spp. , Enterobacteriaceae spp. , Bacillus spp. , Aeromonas spp., Flavobacterium spp. and Micrococcus spp. could be isolated from 24 % , 16 % , 28 %, 4 % ,4% and 12 % of pasteurized milk samples, respectively. All isolates were tested for proteolytic and lipolytic activities but at varying percentages.
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