Evaluation of different analytical methods to determine grape organic acids

The determination of low molecular weight organic acids in grape juices and wines is important because of their effect on the organoleptic properties (flavour, color and aroma) and on the stability and microbiologic control of these products. These acids allow to monitor the maturation process of grapes and the evolution of the acidity of wines during the different stages of the winemaking process. Within the framework of a study about the influence of cluster light exposure during various stages of fruit development on berry composition, quality parameters were determined. Among them pH, total acidity, tartaric and malic acid contents were analyzed both using chemical and optical techniques. Titratable acidity and pH, tartaric acid and malic acid contents determined by automatic titrator and HPLC technique were compared with data obtained by Oenofoss™ analyzer, a FT-IR spectrophotometer for a rapid and simultaneous quantification of all parameters. A correlation analysis was performed among chemical and optical data in order to evaluate the prediction performance of the FT-IR device. Reliable results were obtained for pH, titratable acidity and malic acid content, showing correlation coefficients R2 ranging 0.769-0.988.