[Enzymatic methods in the analysis of musts and wines]

The enzymatic methods are based on the property of the enzymes to catalyse specifically and reversibly the conversion of certain metabolites. These methods, developed thanks to the industrial preparation of enzymes, can be applied with no major modification to the analysis of drinks. About 15 constituants of musts and wines can now be determined by these methods. If their cost price was not relatively high, their specificity, sensitivity and rapidity would enable them to compete with the most precise of chemical methods. This is why they are only used in analytic oenology when chemical analysis is most specific enough or too laborious. Enzymatic measurement allows one by its specificity to determine the amount of residual sugar that is fermentable in a dry wine and by its sensitivity to verifie the total disappearance of the malic acid of the wine. Its rapidity must make it preferable to the long and not very specific chemical measurement, especially concerning the determination of citric acid. But glycerol, ethanol and acetic acid can be measured by chemical or chromatographical means with sufficient precision and for a more modest price. In oenology the methods are essentially used for research. They have permitted the study of the combinations of sulphur anhydride in wines (measurement of cetonic acids). The determination of the isomeric nature of the lactic acid produced from sugars by lactic bacteria is based on their application; this determination is a criterium for the identification and classification of these microorganisms. The measurement of the lactic acid during vinification allows the early disclosure of the first effects of a bacterial development; inversely it permits the invalidation of the existence of a lactic sourness, which a high volatile acidity might point to. Lastly, the enzymatic measurement of gluconic acid allows the health of the crop to be controlled.