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Explainer Science

Is There Butter in That Chardonnay?

Understanding how malolactic fermentation impacts wine textures and flavors

Meg Maker By December 10, 2021
illustration of bottle surrounded by butter, vanilla and cream
Photo illustration by Pix

Some people hate buttery, oaky Chardonnay but love Chablis and white Burgundy.

The irony is that these wines are nearly identical: They’re all based on Chardonnay, they all age in wood, and they all go through malolactic fermentation.

The haters blame that last step, MLF, for turning their Chardonnay into a dessert course. That’s not quite fair. Malolactic does soften the wine and add creamy notes, but barrel aging also modulates the wine’s flavors and textures. The two can be complementary — or unpleasantly additive. 

How can you untangle what you’re tasting and choose the style that’s right for you?

MLF explained

Malolactic fermentation is carried out by lactic acid bacteria, LAB. Technically, it’s not a fermentation but a bacterial reaction that converts potent malic acid to weaker lactic acid. This raises the wine’s pH, lowers its acidity, and gives it a softer texture.

That transformation itself does not alter the wine’s flavors, since these acids are fixed, not aromatic. But it does alter its texture, resulting in a wine that is less tangy, more rounded and smooth.

However, the MLF reactions do produce a flavorful byproduct called diacetyl. It tastes like butter, and for good reason; it’s also abundant in LAB-cultured dairy products. Different strains of LAB create more or less diacetyl. Common flavor descriptors include butter, cream, and custard.

Higher acid wines end up with less diacetyl, while softer, riper wines get more. A very high concentration of diacetyl is considered a fault, resulting in wine tasting of butterscotch or even rancid butter.

MLF is nearly ubiquitous in red wines, which benefit from the reduction in sharp malic acid. Fortunately, the buttery flavor is less perceptible in reds, whose tannins and body tend to obscure it. 

MLF is more noticeable in white wines, so winemakers use it judiciously to suit their own aesthetic aims.

Malolactic in white wines

MLF is traditional for high-acid white grapes from cool regions. It’s ubiquitous in Chablis and Champagne, for example, used to polish the wine’s sharp edges. Because that fruit is crisp to begin with, the results generally don’t end up fat and buttery.

In some regions, MLF is rare. In Bordeaux, vignerons labor to retain freshness in their Sémillon and Sauvignon Blanc. It’s also suppressed in whites like Riesling, Grüner Veltliner, and Pinot Grigio. Again, some of this boils down to tradition.

Often, it’s a personal stylistic choice. Some winemakers forgo MLF for Albariño, Muscadet, and Chenin Blanc, while others let it roll. Another option is to use it for only a few lots, an approach called partial malolactic. 

Winemakers can block MLF altogether by adjusting pH and temperature, racking, filtering, or adding sulfite. A wine with little or no MLF retains crunchy green apple freshness.

Added complexity

Wood vessel aging of white wine modulates both its texture and its flavors. The results depend on many factors:

  • Type of wood — oak, acacia, chestnut.
  • Source of wood — American, French, Slovenian.
  • Degree of toast — light to dark.
  • Age of vessel — new to well-used.
  • Size of vessel — small barrels have more impact.
  • Duration of élevage — weeks, months, or years.

Some flavors derive from the wood itself, from aromatic esters called lactones. Others are byproducts of barrel toasting.

Common barrel descriptors include coconut, vanilla, nutmeg, clove, toast, coffee, tobacco, caramel, and bitter chocolate. Sometimes barrel notes are herbaceous, like dill or green tea. Another flavor note is just wood, like freshly sawn oak.

A new, heavily toasted oak barrel imparts the most roasty, caramelized, even smoky notes to wines. Meanwhile, a large wooden tank, or foudre, that’s been used for many years is essentially flavor-neutral. It’s not uncommon to use a mix of wood vessels, or to use them in combination with steel and cement, to minimize woodsy flavors. 

Wood vessel aging is also oxidative. The pores of the wood and the headspace in the barrel introduce the wine to oxygen. In white wine, this creates flavors like nut, honey, and even sherry. Oxidative aging also fleshes out the wine’s texture.

Putting it together 

Wood aging and MLF are complementary but also additive.

It can quickly get out of hand. An uber-ripe, low-acid, full-MLF white wine aged in toasty barriques might tempt one to reach for a spoon, not a glass. The style is wildly popular, but it’s not everyone’s cup of Chardonnay.

But a winemaker who picks just ripe, retains the fruit’s acidity, allows some MLF, and uses wood with discretion will end up with a wine that balances richness with refreshment.

Unfortunately for consumers, it’s not always easy to find wines that suit personal taste. A familiarity with regional styles and specific producers can help. It’s hard to tell by the label. 

Unless the label says butter. Then it’s not hard.

Tasting the difference:

bottle of Gautheron Chablis Vieilles Vignes 2019

Gautheron Chablis Vieilles Vignes 2019 ($30)

Winemaker Cyril Gautheron is the seventh generation of his family to work the Chardonnay vines in the village of Fleys. Gautheron vinifies in stainless steel and treats the wine to a modest amount of oak early in its élevage just to give it a little oxygen. The result is silken and satin-textured, with flavors of Meyer lemon, mango, and mandarin orange peel. The finish is long but with a lift of green tea, which might be from the barrel. It’s beautifully balanced, with no single element, whether fruit, wood, or MLF, screaming for attention.

bottle of Abbot’s Passage Sightline Clarksburg White Blend 2020

Abbot’s Passage Sightline Clarksburg White Blend 2020 ($35)

This is an unusual blend, two parts Chenin Blanc and one part Verdejo. The wine aged for 14 months in French oak, one-third new, and did not go through malolactic. The barrel is evident in both the aroma and flavor profile, delivering a sense of vanilla and nutmeg plus a lightly bitter finish with hints of rubbed sage. Because MLF was suppressed, the wine remains crisp, balancing Chenin’s stone fruit flavors with Verdejo’s linear lime-citrus.

bottle of Darioush Chardonnay Signature Series Napa Valley 2018

Darioush Chardonnay Signature Series Napa Valley 2018 ($59)

Darioush leans hard on new oak and MLF to produce an opulent, concentrated wine to please lovers of this style. The fruit was whole-cluster pressed, barrel fermented, and aged for 11 months in French oak, two-thirds new. It went through full malolactic. The aromas mingle pineapple, citrus, cream, and vanilla. The palate is coating but with a zing of tropical, mango-guava acidity. The finish is buttery with a woodsy twang.