Abstract: [Objective] The bitterness of high calcium milk is mainly caused by the hydrolysis of casein by endogenous or exogenous proteases in milk and the formation of bitter free amino acids and oligopeptides. In order to control quality problems caused by proteases,it is necessary to measure the protease activity in milk.[Method] At present,there is no national standard method for detecting protease activity in milk and dairy products. This study introduced a rapid detection method for determination of protease activity in milk and dairy products by UV spectrophotometer-Folin method.[Result] The standard curve range used in this research was linear and meets the test requirements. The results of precision and spiked recovery experiments indicated that the spiked recovery rate was within the normal range.[Conclusion] The UV spectrophotometer-Folin method can be applied to the determination of protease activity in milk and dairy products.

Key words: dairy product, protease activity, bitterness, UV spectrophotometer-Folin method