الفهرس 
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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
laboratory pasteurized at 90 °C 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 °C for 10 days, and the rapid method
(RM),the inoculated plateswere incubated at 210C 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.
pH value. Mean values of pH value for raw milk samples
obtained from farm, markets and pasteurized milk were 6.36 ±
0.05, 6.35 ± 0.04 and 6.44 ± 0.04, respectively.
Methylene blue retl.uon test. There were 20, 16.7 and 27.5%
of examined samples obtained from farm, market and
pasteurized milk of grade I, respectively. While, 63.3, 83.3 and
72.5% of examined samples had grade II, respectively. Also,
16.7% of examined farm milk had grade III.
2. Detection of abnormal milk:
• Modified Whiteside test. There were 86.7, 93.3 and 100% of
examined raw milk samples obtained from farm, market and
pasteurized milk were normal. While, there were 10 and 6.7% of
examined farm and market raw milk samples had grade II,
respectively. Also, only 1% of examined farm milk samples had
grade III.
• Qualitative chloride test. There were 13.3 and 6.7% of
examined raw milk obtained from farm and market were positive
to chloride qualitative test while all pasteurized milk samples
were normal.
Thermoduric psychrotrophic count. Mean values of
thermoduric psychrotrophic count in pasteurized milk samples
using standard and rapid methods were 8.1 x 103 ± 7.8 x 102
and 7.8 x 103 ± 9.7 x 102, respectively. The isolated thermoduric
psychrotrophic were identified as Bacillus cereus (38.64%),
Bacillus subtilis (13.64%), Citrobacter freundii (9.09%),
Micrococci spp. (11.36%), Proteus mirabilis (9.09%), Provedencia
spp. (9.09%) and Streptococcusfaecalis (9.09%).
3. Effect of lactoperoxidase system on viability of psychrotrophs
in raw milk kept at room temperature:
• Activation of lactoperoxidase system by addition of potassium
thiocyanate and H202 at concentration of 30: 100, respectively
will increase the shelf-life of raw milk kept at room temperature
to 22 hours without clot on boiling.
Recommendations were suggested to control the presence of
such organisms in milk to avoid their undesirable changes that
resulted in economical losses, besides the possibility of their public
health hazard.