The Analysis of Non-Volatile Constituents of Wine by Glass Capillary Gas Chromatography*

Abstract

A considerable amount of quantitative and qualitative information on the non-volatile constituents of wine (acids, sugars, and polyols] can be readily obtained, from small sample volumes without prefractlonation, by glass capillary gas chromatography of their trimethylsilyl derivatives. A continuous check on the correct functioning of the method, and in particular on the inertness of the glass capillary and injector, is obtained by the use of two internal standards, whose trimethylsilyl derivatives vary considerably in stability. Any variation in the ratio of the peak areas of the latter derivatives indicates incorrect sample preparation or possible adsorptive/cataiytic activity of the GC system. As a general method, the technique may be applied to other alcoholic beverages.

Growth and Metabolism of Lactic Acid Bacteria during and after Malolactic Fermentation of Wines at Different pH

“…The hydrolysis of sucrose would produce both glucose and fructose, but sucrose was not found in our wine samples even before malolactic fermentation (data not shown). Trehalose is another important wine disaccharide (32) whose hydrolysis would yield glucose. We did not specifically analyze this sugar, but some preliminary measurements indicated that its concentration decreased during malolactic fermentation.…”

Myo-Inositol, Scyllo-Inositol, and Other Minor Carbohydrates as Authenticity Markers for the Control of Italian Bulk, Concentrate, and Rectified Grape Must

“…Since 1990, the International Organisation of Vine and Wine (OIV) has issued specific official isotopic methods (OIV MA-AS-311-05 and MA-AS-312-06) to fight against this practice [7]. They are based on the analysis of the stable isotopic ratios of hydrogen (D/H) and carbon ( 13 C/ 12 C, expressed as δ 13 C) in ethanol distilled after fermentation. These two parameters are completely different depending on whether the ethanol comes from grapes or from exogenous sugars such as beets and cane, due to the different photosynthetic cycles (C3 or C4) of the plants [8].…”

“…Myoand scyllo-inositol are two minor sugars characteristic of grape must [10][11][12], which are not retained by the resins used for the concentration process used to obtain CM and RCM, and these two polyalcohols are not naturally present in other commercial sugar syrups from different botanical origins (e.g., sucrose from beet, cane or sugar syrup from fruits, etc.). Furthermore, scylloand myo-inositol have been described as stable in terms of the storage or processing of juice [13].…”