SIMULTANEOUS FLOW INJECTION ANALYSIS OF L-LACTATE AND L-MALATE IN WINE BASED ON THE USE OF ENZYMES

Abstract

The simultaneous determination of L-malate and L-lactate, by enzymesupported FIA, was developed using two enzymereactors in parallel and a single oxygen electrode. NADH formed in the reaction of malate dehydrogenase (MDH) was regenerated to NAD with dissolved oxygen,using vitamin K3 and diaphorase (DI). L-Lactate was determined using the enzymelactate oxidase (LOD). When sample solutions were simultaneously injected into the two reactors (the MDH-Di-reactor and the LOD-reactor) with a controlled residence time, a train of two peaks corresponding to L-lactate and L-malate were seen in the FIA-gram. The peak currents were linearly related to the Lmalate and L-lactate concentration in the range 0.05-1.2 mM and 0.01-0.5 mM, respectively. The present system was applied to the determination of Llactate and L-malate in white wine. The results showed a good agreement with those obtained using a conventional method (F-Kit method), suggesting that this system may be applicable to the monitoring of malo-lactic fermentation during wine production.