Chardonnay: Aging Derived Compounds

This is the third (possibly last) of the series of blogposts on Factors influencing the aroma composition of Chardonnay wines. My brain is tuned to looking at pictures which gives me a better understanding when facts are provided in that format so I created illustrations from the tables that summarized the compounds that come from (1) the grape, (2) fermentation and (3) aging.
Here are the compounds that come from wine aging.

Aging in oak barrels leads to wine compounds that can arise from:

• extraction of oak volatiles
• contact with lees
• processes associated with the “low oxidation” conditions
• microoxygenation

The most important compounds released by oak into the wine are the cis- and trans-oak lactones. The presence of these lactones is affected by the age, origin, and volume of the barrel.
Benzenemethanethiol (BM) and 2-furanmethanethiol (FFT) at concentrations above the perception threshold were found to increase during aging. BM has been described as contributing “flinty” and “smoky” notes and may be related to Chardonnay's “mineral” character. FFT confers a strong “roast coffee” aroma and is formed from furfural released by oak barrels and hydrogen sulfide during alcoholic fermentation. BM and FFT were found to increase during aging.
Other compounds derived from aging in oak barrels that confer Chardonnay "typicity" include guaiacol, 4-ethylphenol, 4-ethylguaiacol, 4-vinylphenol, vanillin, methyl vanillate, and 5-methylfurfural. Furfural formed in oak during coopering was extracted during fermentation and aging in barrels.
In general, “young wine”, “fruity”, and “floral” characters decrease rapidly in white wine during aging, mostly due to loss of acetate esters and ethyl esters of short-chain fatty acids transforming into forms with less-intense aromas such as α-terpineol.
In contrast, ethyl acetate, diethyl succinate, ethyl lactate, ethyl 2-furoate, ethyl 2-phenylacetate, and ethyl 2-methylbutanoate were more abundant in the older wines.
With that, this concludes the three part odyssey into aroma and flavor compounds in Chardonnay wines. Thanks for sticking around!
References:
1. Gambetta JM, Bastian SEP, Cozzolino D and Jeffery DW., Factors influencing the aroma composition of Chardonnay wines, 2014, J Agric Food Chem 62:6512–6534.
Illustration created from Table 4. Odorants Derived from Oak Contact or Formed during Aging That Are Important to the Typicity of Chardonnay Wines, pg. 6516 of the reference above.
2. Joanna M. Gambetta, Leigh M. Schmidtke, Jiaming Wang, Daniel Cozzolino, Susan E.P. Bastian, David W. Jeffery, Relating Expert Quality Ratings of Australian Chardonnay Wines to Volatile Composition and Production Method American Journal of Enology and Viticulture Jan 2017, 68 (1) 39-48; DOI: 10.5344/ajev.2016.16058