WINETECH Technical Yearbook 2021

OTHER MONOTERPENES Terpenes can be found as free or glycosylated forms in grapes. They are important contributors to Muscat aromas in grapevine cultivars such as Muscat,

also a C 13 -norisoprenoid, smells of spices and tobacco, and is often referred to as “tabanone”. DRIED FRUIT AROMAS Massoia lactone, γ-nonalactone and furaneol , 3-methyl-2,4-nonanedione (MND), and (Z)-1,5-octadien-3-one have recently been identified as compounds contributing to dried fruit aromas in must and red wines. This family of compounds are specifically associated with over- ripening of grapes and are expressed in Several studies have demonstrated the sen- sory impact of substituted esters on fruity expression in red wines, even when these compounds were present at concentrations below their detection thresholds. These esters increase the perception of fruity aromas due to numerous synergistic effects between fruity compounds. OTHER AROMA COMPOUNDS AND COMPLEMENTARY OBSERVATIONS Dimethyl sulphide (DMS) in wine has a varying aroma impact, depending on its wines made from such grapes. SUBSTITUTED ESTERS AND QUALITATIVE FRUIT AROMAS

concentration. At low concentrations it imparts blackcurrant aroma, at medium concentration truffle or undergrowth, and at high concentration green olive or asparagus. It should be noted that there is a positive link between DMS concentration and the ageing bouquet complexity of the most iconic Bordeaux red wines. DMS does not impart fruit aromas, but it does have an indirect impact on fruity aroma expression, enhancing blackcurrant aromas at low concentrations. Aromatic N,S-heterocycles, a large family of wine aromatic compounds, contribute a broad spectrum of aromas ranging from meat to cooked potatoes, roasted coffee or hazelnut. O-aminoacetophenone (AAP) is associated with the untypical ageing character of white wines, particularly in Riesling. Wines showing high levels of AAP reminisce of naphthalene, floor polish, acacia blossom or mothballs and display a metallic bitterness on the palate. CONCLUSION It is known that volatile aromatic com­ pounds are not specific to a cultivar, but rather that their concentration varies depending on cultivars. One example of

this is Riesling wine that contains more TDN than Chardonnay or Gewürztraminer. Aroma compounds i n wi ne va r y considerably with environmental factors such as soil or climate – the influence of cultivar, soil and climatic conditions on a wine’s taste is known as the “terroir effect”. Part 2 of this series of articles will focus on measurable parameters, such as air temperature and vine water status (to name but a few), and how they impact wine typicity. REFERENCE Van Leeuwen, C., Barbe, J., Darriet, P., Geffroy, O., Gomès, E., Guillaumie, S., Helwi, P., Laboyrie, J., Lytra, G., Le Menn, N., Marchand, S., Picard, M., Pons, A., Schüttler, A. & Thibon, C., 2020. Recent advancements in understanding the terroir effect on aromas in grapes and wines. OENO One 4, 985-1006.

Gewürztraminer and Riesling. VOLATILE THIOLS AND C 13 - NORISOPRENOIDS

Although the volatile thiols aroma family was first identified in Sauvignon blanc, it is present in numerous other cultivars. They are present in grapes as non- odorous glutathione or cysteine bound precursors and are released, and thereby becoming aromatic, during alcoholic fermentation by yeast. Important volatile thiols are 3-mercaptohexanol (3MH – grapefruit), 3-mercaptohexanol acetate (3MHA – passion fruit) and 4-mercapto-4- methylpentan-2-one (4MMP – boxwood). C 13 -norisoprenoids, a family of important wi ne a roma compounds , i nc l ude β-damascenone, described by fruity-flowery or baked apple notes and 1,1,6-trimethyl- 1,2-dihydronaphtalene (TDN), which imparts kerosene-like notes. The latter compound is characteristically found in older Riesling wines. Megastigmatrienone,

For more information, contact Bernard Mocke at bmocke@gmail.com.

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