Nature, origin and prevention of hydrogen sulphide aroma in wines

Abstract

The nature and origin of ‘hydrogen sulphide’ aroma in young wines is studied and means sought for controlling and preventing its occurrence. The aroma is due to hydrogen sulphide and traces of ethanethiol and is formed from bisulphite and elemental sulphur, but not from sulphur‐amino‐acids. The amount formed from elemental sulphur is inversely proportional to particle size. Vineyard sulphur dusts and sprays can give rise to hydrogen sulphide if applied shortly before harvest. Yeasts differ in their power to produce hydrogen sulphide during fermentation and prevention depends on the use of a strain selected for minimal production. Low pH and high fermentation temperature encourage formation. Wine stored on its yeast can produce hydrogen sulphide from elemental sulphur but not bisulphite. The presence of several metals is deleterious especially with large amounts of sulphur dioxide. Removal is best affected in the early stages of development of the aroma by addition of sulphur dioxide and aeration. The mechanisms of aroma formation are discussed.

Identification of Genes Affecting Hydrogen Sulfide Formation inSaccharomyces cerevisiae

“…There are various mechanisms through which hydrogen sulfide may be produced by Saccharomyces cerevisiae. H 2 S may be generated through the degradation of sulfur-containing amino acids, the reduction of elemental sulfur, or the reduction of sulfite or sulfate (2,21,31,34). When other preferred nitrogen sources are depleted, Saccharomyces can degrade sulfur-containing amino acids to utilize the nitrogen, resulting in the release of H 2 S or other volatile sulfur compounds as by-products.…”

“…H 2 S is most commonly produced as a result of the activity of the sulfate reduction pathway, in which S. cerevisiae reduces sulfate or sulfite for the synthesis of the sulfur-containing amino acids methionine and cysteine and their derivatives. Inefficiency of incorporation of the reduced sulfur into the precursors of these amino acids has been proposed to result in leakage of sulfide from the pathway and the formation of H 2 S (10,17,31,40). Mutation of this pathway accompanied by methionine supplementation of the grape juice is not a viable strategy for the elimination of reduced sulfide formation since both cysteine and methionine are reactive chemically under these reductive fermentation conditions, leading to a host of other equally undesirable sulfur-containing spoilage compounds.…”

“…Fermentation temperature (21,31), juice turbidity (21), the level of soluble solids (46), and titratable acidity (46) have been shown to significantly affect H 2 S levels. The presence of various constituents such as metal ions have also been suggested to result in increased H 2 S in wine, although this has not been conclusively demonstrated (10).…”

“…Extensive research has provided evidence that the yeast strain, and therefore the genetic background, is an important variable in H 2 S production and that strains respond differently to physiological and environmental factors in the production of reduced sulfide (1,12,13,16,31,41,44,46). As a consequence of this strain variability, it has not been possible to devise fermentation management strategies guaranteed to reduce or eliminate the appearance of H 2 S. Spiropoulos et al (40) grew 29 Saccharomyces commercial and natural isolate strains under three different nutritional conditions and demonstrated not only that H 2 S production among strains differed but also that the response of the strains to the medium conditions varied dramatically.…”

Formation and Removal of Acetoin During Yeast Fermentation

“…In anaero bic yeast fermentation with cells and medium low in essential lipids, oxygen is absolutely necessary for the formation of ergosterol and unsaturated longchain fatty acids,3 which both are essential con stituents of yeast membrane structures. [35][36][37][38] In addition, oxygen may also re-oxidize cofactors within the yeast and in this way affect the fermen tation. 27 The yeast cells may be stimulated either directly by oxygen or by the supplement of ergo sterol and unsaturated fatty acids.…”