IMPACT OF MICROWAVE ON SURVIVAL AND RHEOLOGICAL PROPERTIES OF Staphylococcus aureus IN NUTRIENT BROTH AND BUFFALO'S MILK

Document Type : Original Article

Authors

1 Dairy Science and Technol. Dept., Faculty of Agric., Cairo Univ., Giza, Egypt

2 Microbiology Dept., Faculty of Agric. at Fayoum, Cairo Univ., Egypt

Abstract

Staphylococcus aureus ATCC 25923 suspended in nutrient broth (168 x 104
CFUlml.) and buffalo's milk (85x104 cfu/ml) were placed in glass tubes. Nutrient broth
tubes were exposed to microwave of low (90w), medium (450w) and high (900w)
power for 0, 2, 4, 6, 8 and 10 seconds. Milk tubes were subjected to microwave of
high power for the same exposure periods. The final temperature of the media and
rate of microorganism destruction and the effect of this treatment on the changes of
morphological profile and rheological properties of S. aureus were determined.
Microwave irradiation completely destroyed the microorganism when
exposed for 8 seconds and the 900 w power at a final temperature of 75°C in nutrient
broth and 86°C in buffalo's milk. The athermic effect of the microwave on the
microorganism was supported by the 80% destruction obtained at a final temperature
of 40°C. Microwave heating decreased cell diameter, width, length, perimeter, surface
area, thickness and sphericity and increased cell compactness. These changes
increased by increasing microwave power and/or exposure period. 
Journal of Food and Dairy Sciences
Volume 27, Issue 10
October 2002
Pages 6835-6845

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