There’s fat in your wine, but the fatty acids are the issue

Oil and water don’t mix (unless you add egg, but then you’ve got an emulsion…and mayonnaise). Wine is essentially water plus alcohol, which doesn’t mix well with oil, either. Since there’s no oil slick layer floating on top of your glass of wine the way fat drops glisten on top of a bowl of ramen, you’ve probably assumed that the wine is fat-free. And if you Google “is there fat in wine?” about 102,000,000 results will tell you that you’re right.

Which is wrong, sort of. Wine does, strictly speaking, include very small amounts of fat. New and improved chemical analyses of New Zealand sauvignon blancs have identified that they at least 25 different kinds of triacylglycerides — the chemical reference for your standard fat molecule: three fatty acids (tri-acyl) bound to a glycerol molecule (glyceride). That’s in addition to an assortment of other fat relatives such as free fatty acids and some waxes.

It’s actually the free fatty acids that are most important here. (Those fats are there in such minuscule quantities that even the jumpiest health journalist can’t pretend there’s anything to jump about there.) They’re present in milligram per liter quantities (so we’re talking less than the amount of sugar found even in truly dry wines) which is enough to make a significant sensory impact on wine indirectly. 

Yeast need lots of free fatty acids to grow well; they’re a major raw ingredient for new cell walls. With plenty of oxygen they can make their own; without oxygen, that particular yeast production line shuts down. Fermenting wine is a mostly anaerobic job for yeast: they get a little oxygen exposure at the top of the vat, a little if the wine is vigorously mixed to keep the skins submerged, but mostly need to rely on the fatty acids initially contained in the grape juice to tide them over. If that source fails, a long and very complicated chain of yeast stress response events kick in, ultimately ending in stuck fermentations, icky aromas, or both. In short, the amount and kind of fatty acids in particular and lipids in general affects wine aroma.

That’s not a wholly unheard-of problem. Overly enthusiastic efforts to clarify white juice before fermentation can pull fatty acids out, too, to the yeast’s detriment. But, ironically, the more common issue is too much of the wrong kind of fatty acid after the yeast have been at it awhile. Lacking the ability to synthesize cell wall components they really need, too much of cell wall molecules they can make (decanoic and octanoic acids) accumulate with toxic consequences. The effect fatty acids have on yeast is a bit like the effect fat has on humans: too much of the wrong kind kills us after awhile, but not enough of the right kind can cause serious problems, too.

But there’s a different and possibly more interesting point to be made here. Lipids originally present in the grape juice affect yeast metabolism, which affects wine aroma, which gives us new places to intervene to make alterations. Adding lipids to South Australian chardonnay boosted production of aromatic molecules: esters, aldehydes, higher alcohols, and volatile acids. The authors of that sauv blanc study speculate that adding specific lipids might be a way to create new, different styles of that so very identifiably aromatic wine.

This information is splendid in two ways. First, it tells us more about that complex and ill-described business of how winemaking works. Second, it may be a way to experiment with new wines. But, third, it could open up one more avenue for adding stuff to make wine fit a particular sensory profile, which we might more generally call “manipulation” and to which many of us* are generally opposed but which fuels the contemporary commercial wine-as-supermarket-commodity industry and supplies inexpensive reds and whites to fit market niche-targeted profiles specifically designed for the glasses of middle-class suburban mothers between 31 and 40 or single 22-29 condo dwellers who prefer to drink wine before dinner with friends on Thursday and watch Orange is the New Black. All wine is manipulated, all wine contains fat, but what that means for any individual case is a different question.

 

 

*Assuming, perhaps unfairly, that “us” is mostly comprised of people who prefer to drink and/or help produce unique and expressive wines that rely more for direction on local traditions, personal philosophy, and vintage conditions than Nielsen numbers.