Rapid and accurate determination of malate, citrate, pyruvate and oxaloacetate by enzymatic reactions coupled to formation of a fluorochromophore: Application in colorful juices and fermentable food (yogurt, wine) analysis.

A fluorometric-coupled reaction for the accurate and rapid determination malate, citrate, pyruvate and oxaloacetate is presented. The method was found useful for an accurate and rapid determination of these metabolites in low volumes of milk, yogurt, apple and lemon juice and wines without considerable pretreatment. In particular, this method was found valuable in characterising the outcome of maloactic acid fermentation (MLF) in wine and outlined for the first time fundamental differences in MLF between red and white wines. Thus, this method has merit in analysing these substances in heterogeneous, opaque and colorful foods.