Chardonnay as a varietal is synonymous with the flavors of apples, pears, cinnamon, butterscotch, oak, and butter . Grapes and grape skins, are naturally prevalent in tart malic acid and give chardonnay many orchard fruit flavors. Oak delivers toasty and baking spice qualities.
Malolactic acid conversion is a unique process in winemaking that gives chardonnay a distinct buttery quality. It is essentially converting malic acid to lactic acid (also found in milk), a process to smooth a harsh acid to a mellow one. It is like tasting skim milk versus whole milk. This process is often incorrectly referred to as a secondary fermentation while the wine mellows in oak barrels.
In wine geek-speak; malolactic conversion is often referred to as malo, ML, and malolactic fermentation. It is not technically fermentation because it does not produce alcohol as a byproduct, though it does produce carbon dioxide as a byproduct. This is where the fermentation is easily confused. It is not converting any sugars to alcohol. For all of the chemists out there it is technically a decarboxylation. The other byproduct of malolactic fermentation is diacetyl, which is a byproduct from the yeast, and gives chardonnay buttery and butterscotch flavors.
In winemaking, a chardonnay that has not undergone malolactic acid conversion will have more of a green granny smith apple quality. These chardonnays usually receive little or no oak and are a great aperitif wine. They pair well with fish and shellfish. Chardonnays from Chablis are usually made in this style.
Chardonnay that has undergone malolactic conversion will have a buttery and red delicious apple quality. The buttery texture is a result of converting one acid to the next. These chardonnays usually have significant oak influence. The cinnamon and vanilla flavors are not from the grapes or fermentation process, but from the influence of oak. These chardonnays pair well with roast chicken, buttered popcorn, (personal favorite) and cream sauces. Chardonnays from Russian River Valley, Montrachet, and Sonoma County generally reflect this style.