When wine grapes are medicine, forgotten varieties deserve a second look

Autocthonous, adj. – Indigenous to a particular environment, habitat, or geographical area.

Italy, like other places that have vineyards substantially older than their nationhoods, mothers a gobsmacking number of unique, local, autocthonous grape varieties known only to village natives and sleep-deprived MW students obliged to memorize them all. At the risk of offending, most aren’t famous for good reason. International grape varieties (cabernet sauvignon, merlot, riesling, and the like) become international in part because they grow well in diverse locales, in part because of accidents of history, but in part because they tend to make darn good wine. Even as the recent fashion for weird, little-known, and hard-to-get wines means that hyper-local varieties are hearing their names uttered in distant lands (like London and San Francisco wine bars), they’re a niche interest at best.

Nevertheless, lots of scientific work has recently been going into documenting these autocthonous grape varieties. A cynical observer might attribute that to the necessary technology being newly cheap and still trendy, a less cynical one to our renewed appreciation for biodiversity. We could even end up rediscovering lost talent and invigorating new wine styles, like finding the greatest novel of the 20th century as a manuscript in the bottom drawer of your great-aunt’s writing desk and giving it the publication run it always deserved. While we’re waiting for that to happen, there’s actually a different and you might say nobler motive at work. Biologists are hunting for medically useful compounds, and Frosinone in Latium in Central Italy has become their new Amazon rain forest.

Italian biologists have been scouring their countryside for “local, ancient ecotypes” and, beyond the usual business of documenting whether they’re genetically unique, a recent paper takes the extra steps of measuring their concentrations of antioxidant phenolic compounds and observing their effects against proliferating cancer cells. Having first ranked their 37 autocthonous Frosinone varieties by anti-oxidizing and free radical-fighting capacity, they threw concentrated seed extracts at model cancer cells growing in lab dishes. And some of the cancer cells died or stopped growing!

Now, dead cancer cells floating in dishes are clearly a very, very, very long way from wine grape seed extracts being used as the next cancer-fighting miracle drug. But. Compounds from wine grapes likely will (continue to) be investigated as medications. And no matter whether Zimavacca or one of the numerous unnamed “new genetic profiles” from this study become the trendy new somm-bait, we have good reasons to preserve such things. Analyzing samples from odd nooks about the countryside shouldn’t need economic justification: preserving our cultural-biological history is a good fight. But in the present climate, a little economic justification doesn’t hurt.

The value of cold soaks for red winemaking; the value of cold soak research for winemakers

Cold soaking seems to be an especially divisive winemaking technique, at least in the Pacific Northwest, and that’s saying something in an industry full of strong personalities. Cold soakers say that allowing crushed red grapes to rest for one to several days in an environment too cold for Saccharomyces activity, before warming everything up to yeast-pleasing temperatures and allowing fermentation to begin in earnest, deepens color and augments flavor and tannin extraction. The anti-cold soak camp claims that these benefits aren’t real and sometimes adds that cold soaks allow for the dangerous possibility — dangerous, that is, if you’re also in the anti-spontaneous ferment camp — of illicit microbial growth before winemakers inoculate commercial yeast strains at the soak’s end.

Research to date has been unhelpfully mixed. Some studies show increased phenolic (color and/or tannin) extraction, some don’t, some even show lower phenolics following cold soak, and the variables responsible for the differences haven’t yet been worked out. Adding to the confusion is the inevitable mess that follows pro-spontaneous from anti-spontaneous fermenters, since the non-Saccharomyces activity that might occur during cold soaks is a source of desirable complexity to some and unconscionable spoilage to others.

I would love to say “until now” and herald the arrival of a brilliant, conclusive paper outlining a robust explanation for how and why and where and when cold soak works. My inability to do so isn’t likely to come as a surprise. Nevertheless, there is new research and, while far from once-and-for-all conclusive, it helps, if perhaps not in the expected way. A new study from an Argentinian team* tested cold soak on cabernet sauvignon, merlot, syrah, pinot noir, malbec, and barbera d’asti, looking for differences both when the wines were pressed and after a year of bottle aging. Cold-soaked wines saw four days of 6.5-11.5ºC (44-52ºF) courtesy of periodic dry ice additions, then 10-day fermentations at 21.5-26.5ºC (71-80ºF); control wines went straight to 14-day fermentations. All varieties were made in the same way: same full twice-daily pump-overs, same twice-daily punch downs. All were inoculated with the same commercial yeast strain five hours after crush. Regrettably, the study didn’t include multiple variations on the cold soak theme — different times, temperatures, or techniques — that might have helped to suss out where any cold soak differences are happening and given much more information to winemakers. In particular, it’s important to emphasize that chilling with dry ice meant as much as a 10ºC (18ºF) difference in temperature between different parts of the tank because the dry ice clumped. Jacketed tanks would have applied a more uniform treatment.

The agglomerated results were straightforward enough. Cold soaks increased color density, but didn’t increase phenol or tannin concentrations. Cold soaking also didn’t make a statistical difference to any basic wine chemistry parameters: ethanol concentration, pH, acids, glycerol, and residual sugar. Tasters found that the most important difference between all of the wines was driven by grape variety, though that’s hardly meaningful and says nothing about cold soak. That’s the big picture.

The details in the supplemental data attached to the main paper show something more interesting. Each variety responded a bit differently to the cold soak treatment. In the barbera and the syrah, tannin concentrations actually were higher in the cold-soaked wines. The opposite was true for the pinot noir, where cold-soaked wines measured tannin concentrations statistically significantly lower than the control. Cold soaking related to increased total phenols in cabernet, decreased in pinot noir.

What this says to me is that we’re measuring the wrong construct at the wrong level of detail. Asking whether “cold soak” works seems to be the wrong question. Instead, we need to be testing out different potential cold soaking parameters in specific grape varieties to identify what precisely makes a difference and what is moot. This is the kind of data that could really help winemakers who through the lens of their communal experience are saying that cold soak sometimes makes a noticeable positive difference and sometimes doesn’t, and who might reasonably look to science to help them figure out what features separate the worthwhile instances from the useless ones. Unfortunately, if the research question continues to be “Does cold soak increase phenol concentrations?” instead of “Under what conditions does cold soak make a difference to phenol concentrations?” we’re likely to continue seeing confused yes-no-or-maybe reports instead of useful, applicable explanations of what winemakers seem to observe.


*Including Federico Casassa, who has in the past published excellent phenol-related research with James Harbertson at Washington State University, including the American Society of Enology and Viticulture’s 2014 Best Enology Paper of the Year, on the phenolic effects of extended maceration and regulated deficit irrigation, the full text of which is freely available here.