Without yeast, we would have no coffee, no chocolate, our bread would be unleavened, our cheeses would be flavourless, and our would be one without beer or wine. And after thousands of years of coexistence, we are still trying to unveil the secrets of these single-celled organisms. A voyage into the world of fermentation, in the laboratory of Château Palmer…
The first time Hervé Klebanowski peered into a foaming, fragrant, fermenting vat of wine must, he knew he’d found his career. Throughout his studies in chemistry at the University of Bordeaux, Hervé had never ceased to look at the periodic table in awe, seeing not an arcane code of letters and numbers, but the building blocks of life. After graduation, while his more pragmatic classmates headed off to the oil or pharmaceutical industries, Hervé applied for an internship at an oenological laboratory in Bordeaux’s Right Bank. “Soon after came my first contact with fermentation in a winery. I’ll never forget the incredible aroma, this mix of CO2 and fermenting sugars, and that moment you open the vat and see it bubbling, moving, breathing, and you realize that it’s alive.”
“I'll never forget that incredible aroma, or that moment when you open the tank and realize it's alive.”
Hervé Klebanowski — R&D Wine Château Palmer
Twenty-five years later, Hervé has made studying the origin of that life his profession, as the head of wine research and development for Château Palmer. There, he manages the winery’s state-of-the-art laboratory, which enables the estate rigorously to monitor every vintage, from grape to bottle, in microscopic detail. “Look at a drop of wine must through the microscope and you see these rounded forms, some perfectly circular and others oval in shape. Those are the microorganisms responsible for fermentation – the magic of yeasts.”
For thousands of years, that magic was attributed to deities, from the Sumerian goddess Ninkasi to the Aztecs’ Tēzcatzontēcatl, to Bacchus of Rome. Then, in 1680, Anton van Leeuwenhoek caught the first glimpse of these curious floating globules in drops of beer under a microscope. But not until the nineteenth century did scientists imagine that the globules were unicellular organisms linked to fermentation. The German biologist Theodor Schwann called them Zuckerpilz (sugar fungus), and in 1838 his colleague Franz Meyen provided their Latin name: Saccharomyces cerevisiae. Finally, in 1857, France’s Louis Pasteur proved definitively in a series of pioneering experiments that yeasts were the living catalyst for transforming sugars into alcohol.
One hundred and sixty years later, our fascination with these tiny members of the fungus kingdom has hardly diminished. The entire genome of Saccharomyces cerevisiae has now been decoded, yet scientists are still unravelling yeasts’ role in winemaking. “It’s not just alcohol; a wine’s aromas are also at play,” says Hervé. “In the grapes, there are aromatic precursors with no smell or taste, yet during the fermentation they are released, becoming volatile, thanks to yeasts. Even after yeasts die they continue to influence the wine; as their cells break down they release polysaccharides, magnifying the wine’s body.”
To shine a light on these minuscule beings of great import, today leading estates are taking microbiological analysis to a level far beyond Petri dishes and epifluorescence microscopes. So it is at Château Palmer, when a week before harvest Hervé, assisted by the vignerons and the entire cellar team, starts work preparing a pied de cuve – a fermentation-starter made from the endogenous yeasts naturally present in the vineyard. Compared to simply inoculating one’s grapes with a single commercial yeast culture, it’s an eminently more complex – though rewarding – undertaking. To begin with, grapes are collected from the estate’s best parcels and placed in several special mini-vats. “When we crush and macerate the grapes to launch the fermentation, a competition begins. Because there are lots of yeasts present on berries’ skins – Saccharomyces cerevisiae are the best fermenters, but there are also yeasts of the Candida, Pichia, Lachancea, Kloeckera Apiculata genera – they too will contribute to the wine’s aromatic complexity. But some yeasts, like Brettanomyces, are problematic and cause off aromas. So we analyse all the pieds de cuve to choose the one with the most desirable yeasts, which will then be used during harvest to launch every fermentation in the best of conditions.”
Hervé will draw on an array of powerful technologies, from a PCR analyser, which rapidly assesses the quality and quantity of yeast strains such as Brettanomyces by amplifying a targeted DNA molecule, to a GC/MS/SPME system. The latter is capable of identifying soil samples from the planet Mars, but here serves notably to probe wine for the presence of any undesirable molecules, such as volatile phenols that can mask the wine’s aromas. “Ultimately, these tools all serve a common purpose: to help us better understand this diversity of microbial life, so that we can bring out the best that nature has to offer us.” It’s a challenge that’s repeated vintage after vintage, an unending quest to create the finest wine possible by collaborating with the denizens of a nearly invisible world.
And so endures a primal partnership, as old as the dawn of agriculture. The botanist Nicholas P. Money has even argued that yeasts shaped civilisation, providing humanity – notably via the pleasures of food and drink, which they brought us – the incentive to quit our nomadic lifestyle and settle in villages, surrounding ourselves with fields of barley and hills of vineyards. As Claude Lévi-Strauss put it, the invention of brewing marked humanity’s passage from “nature to culture”. In that sense, yeasts are humanity’s link between present and past, between modern life and our deeper nature; they are the ferment that awakens us to the circle of life.
