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摘要
Copper soap colorimetry is a common way to determine the free fatty acids of grain. However, when determining the lipase activity of grain by copper soap colorimetry its accuracy is frequently affected by the degree of mixedness between lipase and substrate. Grain lipase extraction and purification steps are quite cumbersome as well. To overcome these shortcomings, a modified colorimetric method was established for the determining of wheat germ lipase activity in a low-aqueous media. First, we partially defatted wheat germ, then adjusted it to a certain water activity, added some olive oil, extracted the free fatty acids after incubating for a period of time, then determined the absorbance of reaction system by copper soap colorimetry. Finally we obtained the activity of wheat germ lipase by calculation. The optimum conditions were: coordinated the water activity of wheat germ to 0.84, the addition of 0.75 ml olive oil per gram wheat germ and incubation for 4 h at 55 degrees C. It was calculated that the lipase activity was 3.25 U/g, and the relative standard deviation was 5.82% (n=10). This method eliminates the steps of lipase extraction and purification. Compared with the traditional methods, it is simple, rapid and reproducible.
