Method validation of enzymatic ammonia method and colorimetric free amino nitrogen method applied to wine industry

Abstract

The branch of enology is one of the most complex areas in the alcoholic beverage field. Nowadays there is still much information to discover about microbiological processes which occur on must fermentation. Year after year, enology industry is developing new methods to control and optimize fermentation in order to obtain very specific sensorial characteristics. Since the 90's, wine makers have focused on strain yeast to achieve the required characteristics. But right now experts seem to aim that nutrient addition has also a relevant role. Huge varieties of nutrients are entering the wine market and consequently, are taking importance in wineries. The necessity to analyse assimilable nitrogen is irrefutable and new methods are being implemented. In this work, it was studied the reliability of two methods for nitrogen analysis: ammonia nitrogen by enzymatic method and free amino nitrogen by NOPA method. Both methods are spectrophotometric methods and the sum of both results gives to analyst the yeast assimilable nitrogen. Neither of these methods is present in O.I.V. (International organization of vine and wine) compendium of international methods for wine and must analysis. However, nowadays there are a lot of wineries which wager for them. Principal benefits of these methods are the analysis speed, the easy automatization and the diminution of human mistake. This project guarantees the main analytic parameters needed to implant these methods as reliable methods. Linearity, limits of detection, exactitude and robustness were studied to validate them. Methods were verified for different kind of samples; water, must, finished wine, fermenting wine and also the nutrients addition effects over previous samples