An Enzymatic Method for Determination of Zinc in Milk and Dairy Products

Abstract

In this study, an enzymatic zinc determination method based on the regaining of the activity of apo carbonic anhydrase has been presented. The method was applied to some milk and its products to determine the amount of zinc. For this purpose, milk, cheese, yogurt, ice cream and butter in Erzurum were taken and the zinc concentrations were determined with an enzymatic method. Carbonic anhydrase was purified by a Sepharose-4B-L tyrosine sulphanilamide affinity chromatography from bovine erythrocytes. The zinc, in this enzyme, was removed by dialysis against dipicolinic acid resulting in apo carbonic anhydrase was obtained at a ratio of 100 %. The regaining activity of the enzyme was determined by the esterase activity on p-nitrophenylacetate. For comparison, the same samples were analyzed in an atomic absorption spectrophotometer (AAS). When the result of the AAS were compared with the enzymatic method, a positive correlation between two methods was observed. This suggests that enzymatic methods can be used in some milk and dairy products.