ENZYMATIC DETERMINATION OF LACTOSE AND GALACTOSE IN FOODS - NMKL COLLABORATIVE METHODS PERFORMANCE STUDY

Enzymes are widely used in food chemistry as analytical tools, An enzy matic method for determining lactose and galactose in foods was evalua ted in an interlaboratory methods performance study by 12 laboratories in 4 countries, The method is based on enzymatic hydrolysis of lactos e and enzymatic oxidation of the hydrolysis products. The exchange of the coenzyme in the second reaction is the basis of quantitation, The method may be used for various types of foods, such as liquid and soli d milk products, meat products, cereal products, fats, dressings, swee ts, chocolate, and foods for special dietary uses, It is also applicab le to lactose-free foods but not to products in which lactose has been partially hydrolyzed enzymatically to glucose and galactose, Six comm only used foodstuffs with lactose concentrations ranging from 0.4 g/10 0 g to 40 g/100 g and galactose concentrations up to 0.7 g/100 g were analyzed: crisp rye bread, milk chocolate, sausage, cheese, margarine, and baby food containing milk powder, They were distributed to the 12 participants as 12 randomly numbered test samples, representing blind duplicates of the 6 materials, The relative standard deviations for r eproducibility (RSDR) were between 2.3-11% for lactose and 6.8-50% for galactose.