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KMID : 1007519940030040244
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Food Science and Biotechnology
1994 Volume.3 No. 4 p.244 ~ p.248
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Determination of Milk Protein Hydrolysis in Cheese by Trichloroacetic Acid and Phosphotungstic Acid Soluble Nitrogen
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Kim Mi-Sun
Norman F. Olson
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Abstract
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The 12% trichloroacetic acid (TCA) soluble nitrogen (N) and 5% phosphotungstic acid (PTA) soluble N concentrations in rennet-coagulated caseins increased with time. The rate and extent ofincrease in TCA soluble N was proportional to the amounts of enzyme added. Cheese containing neutral fungal protease exhibited the greatest increase in the level of TCA soluble N above that in the control. Addition of freeze-shocked Lactobacillus helveticus also increased TCA and PTA soluble N concentrations. Fungal proteases released more TCA and PTA soluble N than L. helveticus. A synergistic effect on generation of TCA soluble N was observed when the combination of fungal proteases and L. helveticus was used. The data illustrated the limitations of relating PTA soluble N levels to the age of cheese or the degree of ripening of cheese. The correlation coefficient between salt-in-moisture (SIM) contents and the slope of regression equation of 12% TCA soluble N over the time intervals tested was highly negative (-0.8813) indicating the higher SIM the slower the proteolysis of caseins in cheese. However, the slopes of regression equations of PTA soluble N contents did not correlated with changes in either SIM or moisture contents.
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