Rapid enzymatic determination of lactose in food products using amperometric measurement of the rate of depletion of oxygen

Abstract

An enzymatic method for the rapid and inexpensive measurement of free lactose in food products is described, based on the amperometric measurement of the rate of consumption of oxygen when lactose is hydrolysed by β-galactosidase, followed by oxidation of the product glucose in the presence of glucose oxidase and molecular oxygen. A Beckman glucose analyser with a Clark oxygen electrode is used for signal processing. Only minor pre-treatment of the sample, with no reaction incubation, is required. The measurement normally takes less than 5 min for samples that do not require extraction. The results are precise and accurate. Results for the analysis of milk and powdered milk samples are compared with those obtained by a phenol-sulphuric acid method.