A cautionary tale of mice, microbes, and mechanical harvesting

Short: A recent medical report indicates that fresh juice from mechanically harvested grapes can (on very rare occasions) carry infectious diseases from animals picked up and crushed by harvesting machinery.

Long: Winery work is dangerous. Especially (but not only) during harvest, wineries are production facilities with heavy objects, slippery floors, potentially hazardous chemicals, machinery with moving parts and, often, forklifts. The positive side of that situation is that winemaking professionals know that winemaking — like any similar form of factory or food production work — is dangerous, and they take steps to mitigate risks. An enormous part of mitigating risks is knowing what those risks are, which is why a recent letter to the editor about mechanical harvesting in the New England Journal of Medicine is worth knowing about.

Potential dangers of mechanical harvesting are usually discussed in terms of dangers to the grape vines (of being beaten up by the machines), to the wine (though mechanical harvesting is far from being always a bad thing for quality) or, maybe, to vineyard soil compressed by heavy machinery or animals caught by harvesting equipment. Endangering animals, however, might on rare occasion also endanger humans — and not just if a harvester has an inadvertent run-in with a neighbor’s cat. Some critters commonly found around vines can carry diseases that affect humans.

When six of 29 harvest workers employed at a vineyard in Rhineland-Palatinate, Germany, came down with the same symptoms — trouble swallowing, swollen lymph nodes in the neck, diarrhea, general aches and chills — regional specialists worked them up for infectious disease and came down with a diagnosis of tularemia. Tularemia is what happens to humans when infected by a bacteria, Francisella tularensis, carried by some rabbits and rodents. Most cases occur in hunters. Symptoms vary with how the bacteria entered the body, but the bacteria are never transmitted from human to human, only from animal to human. Or, in this case from animal to grape juice to human. All six workers who became sick remembered drinking fresh juice from the same load of mechanically harvested grapes before becoming sick. Epidemiologists found DNA from F. tularensis and from common field mice in the freshly fermented wine made from that batch of grapes.* Their concluding hypothesis was that an infected mouse or two had been picked up by the harvester and crushed along with the fruit, contaminating the fresh juice.

The wine was confiscated and prohibited from sale, needless to say, though probably without real cause. Infectious disease transmission via wine is unheardof, thanks to the combination of high alcohol and low (acidic) pH that makes wine an inhospitable environment for could-be pathogens. Though I don’t know (and I’m not sure anyone knows) about F. tularensis‘s ability to survive in wine, it’s important to note that the epidemiologists found F. tularensis DNA in the wine, not intact infectious bacteria, and that workers suffered from drinking grape juice, not wine.

The authors of the NEJM letter — most of them German public health officials — concluded that “raw food stuff should be treated before consumption.” If that means “we recommend that you don’t drink fresh juice from mechanically harvested grapes,” that sounds pretty reasonable. Like recommendations about not eating raw cookie dough, many will choose to accept the risk; a lot of us will accept the very small chance of getting ill from bacteria in raw eggs or raw flour for the sake of the certain pleasure of enjoying delicious cookie dough. But, importantly, we know that the risk exists, and if we become sick we might even think to tell our physician about what we ate, which could speed up receiving appropriate treatment.

Tularemia is endemic but rare across the United States and Europe (it’s mostly a Northern Hemisphere disease), with only a few hundred cases per year across the United States. The lesson here would NOT seem to be “don’t drink fresh mechanically harvested grape juice or you might get tularemia” but, rather, “know enough about your environment to have a clue about what might have happened on the very, very rare occasions that something goes wrong.” Also, watch out for mice.


*Did any of the harvest workers remember seeing field mice in the vinyard, and did anyone in the cellar see a dead mouse or two pour into a fermenting vat? Unfortunately, the public health officials who wrote the report didn’t say.

What is the terroir of synthetic yeast?

I recently published* an article with the unlikely-sounding title “What is the terroir of synthetic yeast?” The piece is open-access for anyone to read at Environmental Humanities, though it relies on a fair bit of jargon-heavy social science theory. For that reason (and plenty of others), many people might not get past the title. And reading only the title, you might well think that I’m talking about wine made with synthetic yeast and its special bouquet de la laboratoire.

But you cannot buy wine made with synthetic yeast. Much wine is made with commercial wine yeast, genetically improved through careful breeding for desirable traits through what is fundamentally a centuries-old process of controlled mating and selecting progeny with desirable characteristics for further mating. In the United States, Canada, and Moldova, you may also find wine made with one of two genetically modified yeast strains (GM yeasts are illegal for winemaking purposes elsewhere), constructed by molecularly inserting a small number genes into yeast genomes using techniques only a few decades old.

The creature known as synthetic yeast, in contrast, is—or, rather, will be—the result of making comprehensive changes across an entire yeast genome, building whole chromosomes following the plans for that comprehensive redesign (find more detail here). “Synthetic yeast” will be the product of assembling those redesigned chromosomes in a single little yeast body. Six of sixteen chromosomes are complete with the remainder well on their way to completion.

Even then, however, synthetic yeast-fermented wine won’t be hitting the market anytime soon. An in-progress version of synthetic yeast engineered to produce raspberry ketone has been used to make raspberry-scented chardonnay, but that experimental wine can’t legally leave the lab. So what does its terroir have to do with anything?

Terroir, roughly “sense of place,” is about connection. (Terroir is also used as a euphemism for “this is schmancy wine and you should buy it,” and occasionally as a way of politely saying “I think this wine tastes like dirt,” but I’m not interested in those uses here.) Terroir—the perceived ability to taste that a wine is from a particular winemaking locale—is about using the experience of drinking wine as a means of creating connection between you, the drinker, and a place, a tradition, and a sense of unique identity.

Synthetic biology and other genetic biotechnologies applied to making food are, in contrast, about calories and nutrition or about technical improvement (and, at a different level, about making money for biotech companies). Synthetic foods are placeless; they come from noplace** and can, at least in theory, go anyplace. Some future synthetic yeast might make “better” wine, if “better” is defined in terms of technical perfection rather than uniqueness of expression and connection to tradition. Engineered yeast and algae might in some future world possibly deliver complete proteins to hungry people, but might also encourage policy-makers to think of food only in terms of delivering calories and forget or dismiss its many more-than-caloric roles.

What is the terroir of synthetic yeast?” isn’t necessarily a question with an answer. But it is, I hope, a way of enjoining that as we build the future, we build a place in which food is still about building connections, and that we resist employing technologies in ways that estrange us as eating and drinking bodies from the places in which we live.

*Published recently, but written well over a year ago, as academic publishing in the social sciences and humanities often goes. Speed is important in the natural sciences, where multiple groups may be competing for precedence and where researchers tend to work in large groups publishing many papers so that it’s important to have finished results published quickly so that later papers can cite them. In social sciences and especially in humanities, both of those conditions are less likely to be true: researchers are rarely in direct competition (for reasons too complex to detail here) and people tend to work individually and to gestate new ideas at a slower pace. I originally wrote and presented this paper at the 2016 Symposium for Australian Gastronomy, a beautiful and enthusiastic gathering of researchers, producers, and splendid Australian comestibles.

**Of course, they have to come from somewhere, even if that somewhere is carefully de-emphasized. Terroir, as I mention in the article, is also a reminder that peculiar local conditions of production matter to the products of science and technology, too, not just for artisan agriculture.

Making invisible things visible: Do yeast cells stick to cork during bottle aging?

Yeast do not seem to form biofilms on the bottoms of corks when they’re used, rather than metal crown caps, to secure Champagne bottles during their in-bottle secondary fermentation. This, at least, is the conclusion of an article in the current issue of the American Journal of Enology and Viticulture (paywall), in which Burgundy-based authors investigated the question for the sake of understanding whether Champagne producers, some of whom are using cork for their longer-aging wines, risked upsetting in-bottle fermentation dynamics. After a year of bottle fermentation and aging, a few cells apparently got caught in porous crevices of the cork, but systematic growth presaging the tenacity of a biofilm wasn’t happening.

That finding will no doubt interest the odd sparkling wine producer. Much more interesting is the method they used to make “invisible” cells visible and so reach that conclusion.

How do you determine whether a microbial biofilm is growing somewhere? Continue reading