Yeast and bacterial modulation of wine aroma and flavour

Abstract

Wine is a highly complex mixture of compounds which largely define its appearance, aroma, flavour and mouth‐feel properties. The compounds responsible for those attributes have been derived in turn from three major sources, viz. grapes, microbes and, when used, wood (most commonly, oak). The grape‐derived compounds provide varietal distinction in addition to giving wine its basic structure. Thus, the floral monoterpenes largely define Muscat‐related wines and the fruity volatile thiols define Sauvignon‐related wines; the grape acids and tannins, together with alcohol, contribute the palate and mouth‐feel properties. Yeast fermentation of sugars not only produces ethanol and carbon dioxide but a range of minor but sensorially important volatile metabolites which gives wine its vinous character. These volatile metabolites, which comprise esters, higher alcohols, carbonyls, volatile fatty acids and sulfur compounds, are derived from sugar and amino acid metabolism. The malolactic fermentation, when needed, not only provides deacidification, but can enhance the flavour profile. The aroma and flavour profile of wine is the result of an almost infinite number of variations in production, whether in the vineyard or the winery. In addition to the obvious, such as the grapes selected, the winemaker employs a variety of techniques and tools to produce wines with specific flavour profiles. One of these tools is the choice of microorganism to conduct fermentation. During alcoholic fermentation, the wine yeast Saccharomyces cerevisiae brings forth the major changes between grape must and wine: modifying aroma, flavour, mouth‐feel, colour and chemical complexity. The wine bacterium Oenococcus oeni adds its contribution to wines that undergo malolactic fermentation. Thus flavour‐active yeasts and bacterial strains can produce desirable sensory results by helping to extract compounds from the solids in grape must, by modifying grape‐derived molecules and by producing flavour‐active metabolites. This article reviews some of the most important flavour compounds found in wine, and their microbiological origin.

The impact of yeast starter cultures on the microbial communities and volatile compounds in cocoa fermentation and the resulting sensory attributes of chocolate

“…They perform alcoholic fermentation, thereby creating conditions (e.g., production of ethanol and its conversion to acetic acid) that contribute to the death of (Hansen et al 1998;Schwan and Wheals 2004). Furthermore, the production of secondary metabolites by yeast (organic acids, aldehydes, ketones, higher alcohols and esters) is described because of its aromatic properties that contribute to the quality of chocolate (Ardhana and Fleet 2003;Owusu et al 2012;Schwan and Wheals 2004;Swiegers et al 2005). Aldehydes and ketones with desired odors, such as 2-Phenyl-2-butenal, 5-Methyl-2-phenyl-2-hexenal, nonanal, octanal, and 2-Undecanone, which conferred cocoa and fruity notes, were found in both chocolates, though mainly in the inoculated samples.…”

The Aroma of Rojal Red Wines from La Mancha Region – Determination of Key Odorants

“…Guaiacol is associated with medicinal flavours, the olfactory threshold of this compound 10 μg/l (Guth, 1997) was exceeded in all studied wines. Olfactory threshold of volatile phenols 4-ethylguaiacol, (110 μg/l), 4-vinylguaiacol (10000 μg/l) (Swiegers et al, 2005) were not exceeded in any case. Other remarkable benzenic compounds were the shikimic acid derivates, which point out by the elevated sensory impact.…”

“…Other remarkable benzenic compounds were the shikimic acid derivates, which point out by the elevated sensory impact. These compounds are formed by the aromatic aminoacid metabolic routes in plants or by yeasts, also can be extracting from wood (Swiegers et al, 2005). Benzaldehyde, benzyl alcohol and eugenol were other benzenic compounds identified in wines.…”

Multivariate study of the evolution of phenolic composition and sensory profile on mouth of Mexican red Merlot wine aged in barrels vs wood chips

“…This may be due to the fact that young Merlot wine has a berry taste due to the aromas in wine originating in the grapes and fermentation, and when they are compared with wines whichhave gone through wood aging, the wine which was not in contact with wood does not display the effect of oak derived such as smoky aromas or astringency (Casassa et al, 2008, Frangipane et al, 2007Rapp & Mandery, 1986). Aeration during and/or after the winemaking process could result in the increase of acidity in wine (Swiegers, Bartowsky, Henschke, & Pretorius, 2005). Likewise, the aging in barrels led to an increasing of acidity descriptor (month 1) (Supplementary Table 3), since this process allowed passing of oxygen through the pores of the barrel, whereas in aging with chips, the process was not oxidative, therefore the descriptor duration (encompassing acidity) increased.…”