Preparation of Grapes and Extraction of Sugars and Organic Acids for Determination by High Performance Liquid Chromatography

Abstract

A comparison of different extraction procedures for determination of sugars and organic acids in grapes is described. Reliable recoveries during simultaneous extraction of sugars, as well as organic acids, were obtained. The procedure comprised extraction of freeze-dried berries with deionized water for 60 minutes at room temperature, sample:solvent ratios of 1 g dry mass/50 mL water up to veraison and 1 g dry mass/12.5 mL water at ripeness, followed by adsorption on 2 mL anion exchange resin. Good resolution and reproducibility were obtained during HPLC analyses. The mean recovery percentages of glucose, fructose, tartaric acid, and malic acid were 105.10%, 106.08%, 99.33%, and 99.00%, respectively. To prevent deterioration of grapes and interconversions between compounds, the grapes should be freeze-dried and analyzed as soon as possible.