Innovation in sparkling wine production: Trust the yeast

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.

Continue reading

The power of blending: On sherry, beer, and Brexit

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.

Continue reading

Is hedgerow the same as sweaty passionfruit? (The social constructedness of wine at ICCWS, part II)

The International Cool Climate Wine Symposium in Brighton was an excellent chance to sample English wines, and to discover that what New Zealander’s call “sweaty-passionfruit” seems to be what English people – or at least Oz Clarke – calls the distinctively English aroma of an English countryside hedgerow.

Let it be duly noted that I’m not suggesting that Oz Clarke’s mode of description, or his palate, need be considered broadly representative of the English. Moreover, I expect that many of his countryfolk spend more time carrying laptop bags down exhaust fume-sodden city streets than carrying a rifle and a brace of dead waterfowl down “distinctively English” hedgerows. Even still. Hedgerow is a much better fit for an English wine than sweaty passionfruit, and the reverse is true for those New Zealand sauvignon blancs.

We have no absolute language for talking about wine aroma. Advocates for standardized tasting terms sometimes complain about wine writers “just calling a smell whatever” (I’m paraphrasing). Sure, everyone who writes about wine could agree to use the same words – and maybe even to take the kinds of standardized training necessary for us to all use those words in roughly similar ways – but we’d still just be calling a smell whatever. We use analogies. Wine aromas are like passionfruit, or sweat, or hedgerow, which is to say that we use memory to describe wine, which is to say that available and useful descriptions will vary amongst individuals and cultures.

Nothing new here. Plenty of folk will be familiar with efforts over the past few years to devise useful tasting terms for China and put them into use. Describing aromas of jujube or wolfberry seems more productive than trying to teach Chinese drinkers about “blackcurrant” as a wine aroma completely divorced from its associations with blackcurrants drowning in double cream or preserves spread on toast in the morning. At the ICCWS, Marianne McKay of the University of Stellenbosch described related efforts to define South Africa-relevant aroma terms. Most of her undergraduates begin knowing very little about wine, many not even being wine drinkers. Students who have to learn how to assess wine aroma at the same time as learning what to associate with “raspberry” have a harder time learning those assessment skills than students working with descriptors they already recognize. She and her colleagues are working with students to create a South African aroma wheel, which makes incredible sense. (So long as those students will work in South Africa, and one imagines that they can learn European terms later if they move to the Northern Hemisphere.)

The thing about all of these studies is that they assume that wine aromas remain identical while we just exchange one word for another. One Australian-German study actually tested the equivalency of European and Chinese wine descriptors: “dried wolfberry” was a fair replacement for “strawberry preserve,” but “fresh wolfberry” and “raspberry” didn’t match. The ideal is a one-to-one translation of the tasting note, with the sole effect increased understanding (and increased sales, those Australians are surely hoping) amongst their audience.

I disagree. Words aren’t transparent conduits for information. The words we use shape our realities. They direct where our attention travels. They activate memories and associations. We know that memory and smell are connected at the level of brain activity, and so we know that words change the way things smell.

I wonder whether “sweaty-passionfruit” as it’s used to describe sauvignon blanc and “English hedgerow” as it’s used to describe English whites both map to the same chemical compound (3-mercaptohexylacetate, or one of its cousins*), and I hope that Dr. Wendy Parr, who’s been at the center of characterizing what’s unique about the aromas of New Zealand’s signature wines, takes up that question. But even if sensory science says that these descriptors are two different words for “the same thing,” I won’t be willing to say that a mass spectrometer knows more, or better, than Oz Clarke. Not because I have any special love of Oz Clarke or mistrust in the scientific instrumentation, but because the English wine industry is in the process of shaping what’s unique about it’s terroir, and it is, and those hedgerows are part of it. Even if every English person doesn’t spend misty mornings walking down hedgerows, I’m sure that that mass spectrometer never has.