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Effect of Processing Methods on Cholesterol Contents and
Cholesterol Oxides Formation in Some Dairy Products
Meshref. A. Al-Rowaily
Department of Medical Laboratory Sciences, College of Applied Medical
Sciences, Al-Jouf University,
Saudi Arabia.
Abstract
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The effects of pasteurization, boiling, microwaving, processing and
storage of milk and some locally produced dairy products on cholesterol
contents and cholesterol oxides formation were studied and evaluated.
The 7-ketocholesterol were not detected (ND) in all raw milk samples. On
the contrary, heating of milk led to formation of cholesterol oxidation
products (COPs), mostly, 7- ketocholesterol in different quantities. No
significant effect of heating of milk on cholesterol level was observed
with the exception of the ultra-high temperature (UHT) milk prepared
from milk powder heated at 140 ± 1.0°C for 4 sec showed the highest
value of 7-ketocholesterol (80.97 mgg-1), followed by microwave heated
milk for 5 min (31.29 mgg-1), whereas the lowest value was in milk
pasteurized at 85 ± 1.0°C for 16 sec (3.125 mgg-1). Commercial storage
showed no significant effect on cholesterol and 7-ketocholestrol but
lowered cholesterol concentration and increased 7-ketocholestrol level
of UHT reconstituted milk. Cholesterol content of both yogurt and
labaneh strained by centrifugal separator showed significant decrease
while 7-ketochostrol level was increased significantly with refrigerated
storage. The findings are discussed in the context with the results of
previous similar studies.
Key words: Fat oxidation; cholesterol; ultra-high temperature;
pasteurization; 7-ketocholestrol; microwaving; milk products.
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