Silver in the Artificial Aging of Brandies

by Arthur Beavins, Harry E. Goresline, and E. K. Nelson at the Bureau of Chemistry of Soils,
U.S. Department of Agriculture, Washington D.C.

The use of a process which consists of dispersing minute quantities of ionic silver in the liquid is described for the artificial aging of brandy. Brandies given this silver treatment in the laboratory and held for about a week showed a mellowing effect and considerable change in flavor and aroma; the method may be useful for the quick aging of distilled alcoholic beverages.

There was a loss in aroma and flavor when brandies were silver-treated or stored around 45" C. Satisfactory results were obtained when brandies were silver treated at lower temperatures or stored at temperatures from 0" to 37' C. Although there is a change in flavor and aroma brought about by the silver treatment, apparently no significant change, as indicated by chemical analyses, takes place in the acid, ester, aldehyde, or fusel oil content of the brandy.

The quick aging of alcoholic beverages has engaged scientific workers all over the world. The shortening of the timee necessary for the aging process has many economic aspects, since the holding of large quantities of liquor in storage is often a financial burden, and loss due to leakage and evaporation is likely to be serious. Any method which can be operated successfully to shorten this aging period is certain to be remunerative to those employing it.

Many methods have been advanced for the quick aging of alcoholic beverage, employing various materials and devices. These have been reviewed by Fain and Snell. Some of the methods have met with varying degrees of success in practice, but few of them have reached commercial importance. To be successful a method must he economical, effective, and without adverse effect upon the desirable qiialities of a product. In a preliminary experiment the authors found that, when minute amounts of silver were dispersed in a 100-proof alcohol-water mixture, a change similar to "aging" took place within a few days. A vanillin-like aroma was developed, and most of the raw alcohol flavor was lost, giving way to a flavor of rather smooth, delicate character. It was to study the effect of such a treatment on hrandy and other alcoholic products that these studies were undertaken. The authors of this article discuss only the chemical aspects of the subject, and the reader should therefor not infer that either the addition of ionic silver to liquors or the process used is necessarily recommended by the Departnient of Agriculture.

The food and drug laws may restrict such additions entirely and/or may require special labeling.

The apparatus used in these aging studies was a small experimental ionic silver sterilizer similar to those employed in water and vinegar sterilization. The apparatus consists of a hard rubber case holding two silver electrodes between which flows the product to he treated. The ionic solution of the silver is effected by inducing small electrical potential of approximately 1.6 volts of direct current between the electrodes and the liquid. The maximum rate of flow of liquid through the apparatus was approximately 10 gallons (38 liters) per hour.

The various brandies used in these experiments were comercial products. The apple brandy used was 102 proof and the grape brandy 180 proof. The apple brandy was distilled from a pot still and, before being placed in barrels for storage, was passed through a quick ager. This apparatus consists of a small tank charged with toasted oak chips!

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