Buttery: Good in Wine, But a Mistake in Beer

Buttery: Good in Wine, But a Mistake in Beer

by Mark E. Lasbury for Indiana On Tap

Most things about beer are subjective. There are style guides for sure, and people can argue about how closely a beer should follow those guidelines to be considered a certain style. On the other hand, just about anything goes now for beers, and so many beers push the limits of style that it’s hard to see where one style starts and another ends; heck there are NE-style hazy pilsners now!

Likewise, flavors in beer are subjective. What one person considers tasty another might cringe at the thought of. It isn’t right or wrong in the majority of cases, it’s just personal preference. There are beers I like that Walter can’t stomach and vice versa; it’s the reason we rarely buy growlers.

All that being said, making beer is also a science. There are some rules that shouldn’t be ignored, things like cleanliness and adherence to safety guidelines. Certain breaks in technique can be detected by the drinkers, but whether they are recognized as technical errors or just choices with which some people don’t agree is another topic. A beer having off flavors doesn’t mean that there isn’t someone who’d be happy to drink it.

Beer is an art and a craft, but there’s alot of science in there too. image credit: scipubtas.org.au

Technical flaws run the gamut, from the cooked corn flavor from using moist malt or either over-sparging or using a short/less vigorous boil, to a mercaptan flavor from letting the finished beer rest on dead yeast too long. Contaminations with unwanted bacteria can result in souring or butyric acid production (smells like baby vomit); using chlorinated water to clean brewing equipment or leaving any chlorinated sanitizer behind on equipment can lead to the chlorophenol flavor of band-aids or vinyl/plastic.

There are many off flavors that beer judges and beer slingers should know so that they can evaluate beers properly, including one called diacetyl. A diketone compound, diacetyl tastes like the butter flavor from microwave or movie house popcorn. In almost every beer style, diacetyl is considered an off flavor – but not in all styles, the Czechs like some butter flavor in their pilsners, as do some English in their bitters. Nevertheless, if a creamy or buttery flavor is strong in beer, it’s most often considered a mistake in technique —- but not so in wine.

You actually hear people talk about a buttery chardonnay or a creamy white burgundy. This is due to the exact same compound as in beer, but in wine it is considered mostly a positive flavor/aroma, while in beer it is a no-no the vast majority of the time. White wines are more often characterized as buttery because they have less complex aromas and bodies, so the diacetyl comes through stronger than in reds, but it can easily be part of a red wine’s make up.

In beer, diacetyl is the result of incomplete fermentation. Yeast produce diacetyl as a result of making ethanol, but given time they will reabsorb the diacetyl and metabolize it to something else. This means that properly fermented beer goes through something called a diacetyl rest, a period of time for the yeast to get rid of the diacetyl they already made. If the boil is short or less than vigorous, or if the fermentation is at an unreasonably low temperature, the chances of more diacetyl being produced and/or retained go way up.

How to get rid of diacetyl in beer. Let the yeast do it. image credit: Escarpment Laboratories

The key to reduction of diacetyl in beer is to not take the beer off the yeast (racking) too soon. Give the yeastie beasties time to finish their job. In wine, removing the product from the yeast lees early is one way of ensuring that the creamy, buttery aspect will be retained. Of course, it’s never that simple. Wine has additional steps for producing a butter, butterscotch, sweet cream, or cream aspect – it can be described a lot of ways – wine drinkers have a lot of words.

As an aside, the idea that diacetyl tastes like butter isn’t a euphemism, it really does. In fact, for many years diacetyl was the main ingredient in buttered popcorn flavoring. “Was” is the main word there, since it also caused bronchiolitis obliterans, a respiratory disease often called popcorn lung for people who worked with it or were around it constantly. A few people who worked at microwave popcorn factories actually died from popcorn lung. However, there is no danger for people who drink buttery wines or beers, or people who ate artificially buttered popcorn in moderation in the day. Unfortunately, diacetyl is still being used in some e-cigarette flavorings (researchers at Harvard found that 39 of 51 brands of e-cigs contain diacetyl). Weird, the FDA won’t require e-cig companies to submit lists of their ingredients until 2022, but if you want to distribute a beer across state lines, you have to submit the formulation.

It is important to say “diacetyl use in moderation” may be OK because there are always people who takes things too far. One guy was addicted to microwave popcorn and had a habit of inhaling deeply several times over the freshly popped bag before he ate his two bags a day for ten years. Yep, he ended up with popcorn lung. Of course in today’s society he sued the company and walked away with a cool seven million. It’s not hard to see why diacetyl isn’t used anymore in butter flavoring.

But back to our story of how wines become buttery. Diacetyl in wine can come from more than one source. The yeast definitely will produce diacetyl (almost all yeast do), and different yeasts can be picked for more or less diacetyl production. But this is not the main source of diacetyl in wine, it actually comes from bacteria. Lactic acid producing bacteria (LAB, of which there are many) have a metabolic pathway wherein they convert malic acid to lactic acid with a diacetyl byproduct.

Wine tasters have a group of compounds they taste for, but with wine diacetyl is a good one. image credit: Wine Folly

Many wine producers use the LAB and their malolactic fermentation (MLF) pathway to convert the harsher malic acid to a softer lactic acid, but whether or not they go for the diacetyl production as well is something they can control somewhat through which bacteria they use and how long they leave it on the wine. I talked to Marc Rupenthal at Urban Vines/Urban Brews in Westfield about this. He spends his days making both wine and beer (mostly wine now with Derek Kunzman on board for the beer), and he told me a couple of things.

Marc said, “People definitely add LAB to wines with two different goals in mind. One being reduction of malic into lactic. The other being production of diacetyl. Depending on the flavor profile you may choose you might want more of one or the other. The current trend seems to be away from the buttery taste in many wines. Many winemakers now are just using LAB bacteria to turn their malic acid into a less acidic tasting lactic acid and trying to minimize diacetyl production.”

From this I learned that just like pitching their own choice of yeast instead of using the natural yeasts on the grapes for fermentation, vintners also add cultures of various LAB to their wine. Marc added, “Most commercial winemakers pitch their own bacteria because its much more controlled but there are still some who do it the old fashioned and let it happen on its own.” The major bacterial strain used is called Oenococcus oenii, something unheard of in beer brewing except as a contaminant.

Malic acid to lactic acid gives a softer mouthfeel, produces diacetyl, AND gives of CO2. So make sure it is done before bottling wine. image credit: Palate Press

The MLF pathway is a part of the citric acid cycle, so the more citric acid in the wine, the more diacetyl could be made, and other factors, such as temperature, pH, sulfur dioxide levels and aeration can affect diacetyl production via this pathway as well. But even this isn’t the whole story, because there are other factors influenced by MLF.

The LAB also make glucosidases that free up aroma compounds, including diacetyl, from the sugars to which they can be bound. This will add to the buttery aroma of the wines. Finally, MLF can lead to the degradation of acetaldehyde, which can bind up any sulfites added as a preservative, so wines with more MLF require less preservative. So all of these factors can affect the butteriness of a wine, from mouthfeel to aroma and flavor, but so can a barrel.

Since most wines that are looking to be “buttery” are whites, the barrel aging process plays less of a role in their maturation, but barrel aging can increase the diacetyl in a given wine. Oaking a wine harder will add more vanillins, just as in beer, and this can bring out the creaminess of the diacetyl more than in a lightly oaked wine.

While buttery white wines may not be as popular today as they were a few years ago, they still claim a positive spot in the wine world. This is not so nearly true in beer, where diacetyl in most beers will earn you a clear rebuke from a judge and be questioned by some drinkers in the bar. This is just one more thing that separates the wine and beer crowds – who’s right? Everyone and no one – drink what you like.


banner image credit: Craft Beer & Brewing

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