Chardonnay: Fermentation Derived Compounds

Following up on the blogpost Chardonnay: Grape Derived Compounds is today's blog on fermentation derived compounds. The fermentation derived compounds come from the primary fermentation with yeast and the secondary fermentation with malolactic bacteria, yielding many compounds that contribute to the aroma and flavor profile of Chardonnay. Yeasts are not only important in the transformation of sugar to alcohol, but they are also important in the de novo synthesis of important sensory compounds.
During primary fermentation, esters are formed in excess by yeast metabolism and are responsible for “fruity” and “floral” aromas. Acetates are synthesized at higher concentrations than ethyl esters, and the ratio between both, as well as the concentration at which acetates are produced, is affected particularly by:

• fermentation temperature
• must nutrient content
• yeast strain

As the above illustration shows, there are considerably more compounds derived from fermentation than what the Chardonnay grape provides. The most relevant esters for unwooded Chardonnay aroma appear to be ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, hexyl acetate, 2-methylbutyl acetate, and 3-methylbutyl acetate. These compounds located on the left side of the illustration contribute floral, berry, red fruit, green apple, strawberry, and other fruity aromas. Esters formed during alcoholic fermentation constitute one of the main groups of sensorially important compounds in Chardonnay.
When secondary or malolactic fermentation (MLF) is carried out on Chardonnay to transform malic acid to lactic acid, this also produces diacetyl and acetoin which contributes the typical “buttery”, “hazelnut”, and “fresh bread” notes.
Next up, Aging Derived Compounds.
Note November 3, 2017: The illustration that was initially on this post has been updated to correct spelling errors. It has also been organized according to chemical class.
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 3. Characteristics of Odorants Important to Chardonnay Wine Typicity Formed during Alcoholic and Malolactic Fermentation, pg. 6514-6515 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