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Growing up in Pennsylvania, we had stink bugs everywhere—in our house, in our beds, on our dog. It’s rumored the little invasive species hitched a ride to Allentown, Pennsylvania from China or Japan. If they haven’t reached your locale yet, consider yourself lucky. They’re gross little shield-shaped bugs that make your fingers stink when you squish them. It turns out, I have yet another reason to dislike them now: they ruin wine—more specifically, red wine.
The brown marmorated stink bug (BMSB, Halyomorpha halys), which was the focus of this study by Oregon State University researchers, generally migrates into vineyards in August and September, just in time for harvest in North American vineyards. As a result, the stink bugs get carried into the winery within the grape clusters.
The stink bugs are small, camouflaged—and apparently “cryptic”—enough to make detecting the bugs difficult, says a study published in the Journal of Agricultural and Food Chemistry. With the stink bugs undetected, they are processed with the wine.
When grapes are pressed and further processed, we get wine. When stink bugs are pressed, we get stress compounds. Two of the compounds, tridecane and (E)-2-decenal, make up 70% of the overall stinky mix. Tridecane is odorless, but (E)-2-decenal is known for its “undesirable strong green, coriander (or cilantro), and musty-like aromas.” Reaching a certain amount of (E)-2-decenal resulted in “consumer rejection,” so this was what the researchers watched for.
While making white wine, the levels of the stress compound (E)-2-decenal were strongest after a hard press, but (E)-2-decenal appeared to be completely removed during alcoholic fermentation. In red wine, concentrations of (E)-2-decenal were highest after the grapes were destemmed and crushed. Fermentation reduced those compounds, but since pressing occurs after fermentation in red wine, the stress compounds increased again prior to aging.
The experiment also compared live and dead stink bugs, revealing that killing the bugs in the field might not be enough to remove taint from the wine. Unless the bugs were guaranteed to have a blissful experience in the fields. Researchers indicated that “a stressful situation prior to death” resulted in more stress compounds.
Personally, I would have thought that any stink bugs in my wine were too many, but it turns out the magic number is three.The researchers decided on a threshold of three stink bugs per grape cluster for preserving red wine taste. This was considered an average that took into account multiple pressing processes. For white wine, the stink bugs were considered irrelevant to overall taste.
So, the next time you pick up that glass of wine, consider how many of our stinky friends might be hiding inside.
P.S. Happy National Wine Day everyone!
Image Credits: Vaughn Walton/ Oregon State University and the Journal of Agricultural and Food Chemistry
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Re: These Sneaky Stink Bugs Could Ruin Your Wine
