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Abstract
One hundred random samples of raw milk (farm and market each of 30, and pasteurized 40 samples) were collected from Cairo and El—Behera city markets, farms and supermarkets. Raw milk samples were examined for their keeping quality and abnormal milk and then each sample was divided into 3 parts, the first was used for determination of psychrotrophic count, the second was laboratory pasteurized at 63 °C for 30 minutes while, the third part was ahoratory pasteurized at 90 CC for 15 seconds for determination of thermoduric psychrotrophic count, while pasteurized milk samples were examined for thermoduric psychrotrophic count. Psychrotrophic and thermoduric psychrotrophs were determined by 2 methods for each sample. Standard method (SM), the inoculated plates were incubated at 7 CC for 10 days, and the rapid method (RM), the inoculated plates were incubated at 21CC for 25 hours.
1. Keeping quality:
Acidity percent. Mean values of acidity percent for raw milk samples obtained from farm, markets and pasteurized milk were 0,16 ± 0,004, 0.15 ± 0.003 and 0.14 ± 0.002, respectively.
1’ pH value. Mean values of pH value for raw milk samples obtained from farm, markets and pasteurized milk were 6.36 ±
i0.05, 6.35 ± 0.04 and 6.44 ± 0.04, respectively.
Methylene blue reduction test. There were 20, 16.7 and 27.5% of examined samples obtained from farm, market and pasteurized milk of grade 1, respectively.