Talking about nutrition labeling for wine is useful. But a new study (open-access article) assessing consumers’ interest in nutrition info on wine bottles limits its usefulness from the first sentence. The introduction begins, “Alcohol misuse…” Yes, alcohol is misused. But framing research in a way that says that alcohol is important because it is misused colors everything that follows: alcohol is going to be treated as a social evil; alcohol is going to be treated as a drug; alcohol is going to be treated as something that needs to be controlled and restrained; wine is going to be treated as alcohol. Those assumptions are especially out of place when we’re talking about nutrition labels, things usually used for food.
Numerous recent studies have been playing with how yeast can work above and beyond the usual call of duty in sparkling wine production. The Australian Wine Research Institute’s (AWRI) superb yeast biologist Jenny Bellon continues to convince yeast to reshape itself to our needs by breeding across the usual species lines.* Hybrid yeast (open-access article) with a Saccharomyces cerevisiae strain as one parent and a Saccharomyces mikatae or other close cousin Saccharomyces species as the other, generate different secondary metabolites compared with conventional straight-up S. cerevisiae strains, and we somehow end up interpreting that difference as “complexity,” and liking it.
The goal in those cases is to produce new and different (and better) flavors by using these more metabolically complex yeasts for tirage or in-bottle fermentation.
The interesting thing about tirage yeast, though, is that they do a good portion of their winemaking work after they die. While alive, yeast are useful for their insides: the enzymes they house convert sugar to alcohol and numerous other valuable metabolites. In dying, yeast are useful for their outsides: they release mannoproteins from their cell walls that improve wine quality in numerous ways, by enriching mouthfeel, by stabilizing mousse, and by adding lovely bready or toasted aromas. (Find more detail on those effects in this embarrassingly badly written article from 2012).
When yeast cells die, they don’t just turn off; enzymes split open the cell from the inside (autolysis), releasing good-for-winemaking compounds. However, autolysis happens inefficiently under standard winemaking conditions: yeast are most inclined to self-sacrifice around pH 5 and at warmer temperatures; sparkling wine generally sits below pH 3 and is fermented cool. Here’s where two recent scientific studies about innovating in sparkling wine production meet.
Friday saw me thinking a lot about blending. I awoke to the seemingly impossible news that the UK (or, more precisely, English voters, as folks here in Edinburgh will be quick to point out) had voted to leave the European Union. And then I went to work, where we’re exemplifying the power of blending multidisciplinary research teams. I sat in a synthetic biology lab populated by microbiologists, geneticists, automation and biomedical engineers, computer scientists, designers, and me (the resident social scientist), by people from across Europe, Asia, and North America, where we all ended up spending more time mutually coping with Brexit than talking about yeast genetics.
Arguments in favor of the power of blending evidently didn’t win over British separatists. I can’t help but wonder whether Remain would have prevailed if the British population spent more time with good sherry and good beer instead of gulping unthinkingly through volumes of the cheap stuff. Granted, that opinion has a lot to do with the evening’s events after I left the lab, the first of which was an informal sherry tasting.
Sherry conveys one lesson about blending: resilience comes from interdependence. Fino and Manzanilla – “biologically aged” styles – age under a blanket (the unsuspecting would probably say “scum”) of oxygen-dependent yeast. In contrast with ordinary table wines, sherry barrels are only filled partially, leaving plenty of oxygen-filled head space to let flor yeast develop on the exposed surface. That space, plus the hot climate, means plenty of evaporation, which means that barrel volumes are topped up with wine from younger barrels, and so on down the line – the solera system, which also helps build microbial consistency from year to year.