Determination of Cheese Lipase

Abstract

20 g. of Cheddar cheese is suspended in about 100 ml. of water with a power mixer, homogenized several times, and centrifuged. The supernatant is combined with several water washings of the solid residue and diluted to 200 ml. For the analysis, a suitable volume of this extract and 2 ml. of 0.38[image] aniline buffer at pH 5 are mixed and warmed to 40[degree]C. 0.2 ml. tri-butyrin is added and the mixture is incubated at 40 [degree]C for 60 min. 5 ml. aliquots are titrated before and after incubation by the same procedure used in the milk lipase determination (Biol. Abstr. Entry 1080. 1944). One cheese lipase unit is the amount of enzyme giving a titration increase of 0.1 ml. of 0.1 [image] NaOH for a 5-ml. aliquot under the conditions described above. Tributyrin hydrolysis is directly proportional to cheese lipase present when < 0.4 ml. of 0.1 N butyric acid is present in 5 ml. of incubation mixture. The Cheddar cheese lipase system hydrolyzes tributyrin most rapidly at pH 5 with a secondary optimum at pH 6.5-7. Only the lipo-lytic activity at pH 5 is important in ripening Cheddar cheese (pH 5-5.4).