This article was originally posted on RealClearScience.
My wife and I regularly travel to Eastern Europe. Last time we were there, we went to Bonyhad, Hungary, a small town about two hours outside of Budapest. The nominal purpose of our trip was to visit her aunt and uncle; in reality, there was a winery nearby that my father-in-law was dying to show me, which was perfect, because as it so happened, we were running low on booze.
Hungarian wine, specifically Tokaji, is known all over the world. Adventurous sojourners who enjoy vodka would appreciate a shot of Hungarian palinka, as well. My adult beverage of choice is almost any variety of red wine, and my father-in-law and I were in the market for several liters. (No, we’re not winos, in case you’re wondering. We stock up on red wine when given the opportunity since my in-laws live 13 hours away on Poland’s Baltic coast. We fill up whatever we can get our hands on, usually empty water and soda bottles. Yes, we’re classy like that.)
When we get our first chance to knock back a glass or two of that wine, I can’t help but notice the ever-present, but extremely subtle, flavor of butter. And it’s not just me: My wife can taste it, too. Why?
I must first point out that I’m not a wine snob. If given a blind taste test, I couldn’t tell the difference between a Cabernet Sauvignon and a Merlot — or probably even a white wine with red food coloring added to it. I’ve eaten rattlesnake before, which to me tastes just like chicken, and I find Big Macs and filet mignon equally irresistible. So, this isn’t about my refined palate and superior sense of taste. That butter flavor is real.
There are multiple biochemical reactions occurring when grape juice is fermented into wine. The most famous, of course, is the production of ethanol (alcohol) by yeast. But some wines have a secondary fermentation involving a sour* compound called malic acid. Lactic acid bacteria (one of which, called Lactobacillus, is also used to ferment yogurt) can convert malic acid into diacetyl (more properly known as butane-2,3-dione).
And where is diacetyl found? You guessed it: Butter.
Diacetyl was also widely used as a flavoring agent in microwaveable popcorn, but it isn’t anymore. That’s because diacetyl has been linked to respiratory disease (colloquially referred to as “popcorn lung“) in factory workers who make food products like popcorn. A few workers actually died. Still, there is almost no risk to consumers who eat moderate amounts of popcorn, but moderate is the key word.
A genius by the name of Wayne Watson, who ate two bags of microwaveable popcorn every day for 10 years, also came down with “popcorn lung.” He admitted to sticking his face over each freshly popped bag and inhaling like a cocaine addict. He then developed problems breathing and, like any patriotic American, filed a lawsuit against the popcorn manufacturer and the grocery store he bought it from. The jury awarded him $7 million. Yeah, really.
This man’s case, along with those of all the factory workers, prompted manufacturers to remove diacetyl from microwaveable popcorn.
But, it’s still found naturally in all kinds of food, including buttery wine. And that’s just how I like it.
*Note: Malic acid was originally referred to as “bitter,” but “sour” is a more appropriate description.
Source: Brock Biology of Microorganisms (13th ed). MT Madigan, JM Martinko, D Stahl, and DP Clark. Benjamin Cummings. 2010.