Control of Sulphury Impurities in Beer Aroma

Abstract

Volatile sulphur compounds, particularly hydrogen sulphide and mercaptans, are normal products of yeast metabolism. Although they tend to be purged out of beer during fermentation and maturation, it is not uncommon for finished beer to retain enough of them—up wards of 0·02 ppm as sulphur—to impair its aroma. The addition of a small amount of copper sulphate to sulphury beer cleanses its aroma by transforming volatile sulphur into non‐volatile copper sulphide and mercaptides, but since a considerable proportion of this added copper is liable to be inactivated by complexing with nitrogenous constituents of the beer, the removal of sulphur may necessitate the addition of so much copper as to threaten the shelf life of the beer. It has been found that not only may traces of copper be dosed electrolytically into beer with great precision but that the copper so dosed reacts nearly quantitatively with the volatile sulphur present, thus abolishing the latter with no appreciable increase in the net copper content of the beer. The process has given satisfactory results on an industrial scale, improving the flavour of beers without prejudice to their other characteristics.

Hydrogen Sulfide Reactivity with Thiols in the Presence of Copper(II) in Hydroalcoholic Solutions or Cognac Brandies: Formation of Symmetrical and Unsymmetrical Dialkyl Trisulfides

“…In beer, the concentration of transition metals are generally in the range 0.01-1.6 mg/L (Binns et al, 1978;Hough et al, 1982). The presence of copper and H 2 S leads to copper sulfide (CuS) precipitation (Thorne et al, 1970). Thus, the nauseous hydrosulfurous smells are diminished in beer.…”