Adsorbents and Wines. I. Selection of Activated Charcoals for Treatment of Wine

Abstract

A frontal analysis technique is described by means of which it is possible to estimate the relative activities of charcoals in adsorbing various components from wine whether or not the components can be determined by chemical analysis. The ability of 41 different charcoal and carbon samples to remove anthocyanin pigments from a red wine was determined. The volume of wine decolorized per gram by different carbons, divided by the amount of the same wine decolorized by a gram of reference carbon, was determined. The resultant relative specific retention volumes were very similar, as determined on several wines—both dry red and port types. Relative specific retention volumes for brown pigment were also similar between a sherry and a browned sauterne. There appeared to be some general relationship among relative specific retention volumes for red pigment, brown pigment, methyl anthranilate, and the ability of the carbon fo catalyze the air-oxidation of ascorbic acid in that carbons very high or very low in activity for part of these measures were generally similar in activity for the others. A considerable degree of selectivity also was shown, however, by the fact that carbons arranged in order of relative activity according to one of these four tests might have a different sequence of relative activity in the other three. By capitalizing upon selectivity revealed by tests of the type described, the partially preferential removal of brown or red color, or foxy or other odors, from wines appears practical on a rational rather than empirical basis. The ability of charcoals to catalyze oxidation of ascorbic acid could be depleted or consumed by treating them with excess ascorbic acid, but was regained when the charcoal again contacted oxygen. Pretreatment of charcoal with ascorbic acid in aqueous alcohol did not appreciably change the activity of the carbon in decolorizing wine. A means of measuring the oxidizing effect of charcoal on wine and encouraging or preventing this effect is thus provided. Batch treatment of wine with a single portion of carbon equal to the specific retention volume, removed from about 80 per cent to nearly all of the constituent used to determine the specific retention volume.