Enzymes milk pasteurization testing

Alkaline phosphomonoesterase (EC 3.1.3.1). The existence of a phosphatase in milk was first recognized in 1925. Subsequently characterized as an alkaline phosphatase, it became significant when it was shown that the time-temperature combinations required for the thermal inactivation of alkaline phosphatase were slightly more severe than those required to destroy Mycobacterium tuberculosis, then the target micro-organism for pasteurization. The enzyme is readily assayed, and a test procedure based on alkaline phosphatase inactivation was developed for routine quality control of milk pasteurization. Several major modifications of the test have been developed. The usual substrates are phenyl phosphate, p-nitrophenyl-phosphate or phenolphthalein phosphate which are hydrolysed to inorganic phosphate and phenol, p-nitrophenol or phenolphthalein, respectively ... 

Phosphatase Test. The phosphatase [9001-78-9] test is a chemical method for measuring the efficiency of pasteurization. AH raw milk contains phosphatase and the thermal resistance of this enzyme is greater than that of pathogens over the range of time and temperature of heat treatments recognized for proper pasteurization. Phosphatase tests are based on the principle that alkaline phosphatase is able, under proper conditions of temperature and pH, to Hberate phenol [108-95-2] from a disodium phenyl phosphate substrate. The amount of Hberated phenol, which is proportional to the amount of enzyme present, is determined by the reaction of Hberated phenol with 2,6-dichloroquinone chloroimide and colorimetric measurement of the indophenol blue formed. Under-pasteurization as well as contamination of a properly pasteurized product with raw milk can be detected by this test. 

Alkaline phosphatase Phosphatase enzymes are able to split specific phosporic acid esters into phosphoric acid and the related alcohols. Unlike most milk enzymes, it has a pH and temperature optima differing from physiological values pH of 9.8. The enzyme is destroyed by minimum pasteurization temperatures and therefore, a phosphatase test can be done to ensure proper pasteurization. 

The enzyme alkaline phosphatase is naturally present in milk. As it is sensitive to heat it is used to measure the effectiveness of pasteurization. Milk is diluted with a buffer (pH 10.6) containing disodium phenol phosphate which is hydrolyzed by the enzyme releasing phenol. The phenol is reacted with 2,6-di-bromoquinonechloroimide producing a color that is measured spectrophotometrically at 610 nm. An earlier version of this test uses p-nitrophenyl phosphate and the amount of yellow p-nitrophenyl which is released is compared with standard comparator disks. 

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