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- New research suggests ancient winemakers likely relied on naturally sun-dried raisins — rather than fresh grapes — to spark fermentation, thanks to the presence of wild Saccharomyces cerevisiae.
- In experiments, only the sun-dried raisins consistently fermented in water and produced higher ethanol levels, offering insight into how early cultures may have created wine with minimal tools.
- Researchers are continuing to investigate how S. cerevisiae reaches raisins in the first place, while noting that modern store-bought raisins can’t replicate the process because of their protective oil coating.
If there’s one thing we know we share with our ancestors, it’s that we all enjoy a good drink, especially a great glass of wine.
According to archaeologists, humans have been making wine in some form or another for an estimated 8,000 years. While we are fortunate to have technology that helps us cultivate perfect vines, which ripen the perfect grapes, and produce the best wines, those before us had to settle for much less. However, according to a team of Japanese researchers, that’s OK because our ancestors knew how to turn water into wine using just a few simple steps.
In November, scientists from Kyoto published their paper, “Spontaneous fermentation of raisin water to form wine,” in Scientific Reports. In it, the researchers describe how our ancestors used yeasts like Saccharomyces cerevisiae, which, as noted in a release about their work, they said is the “primary species behind the fermentation process that creates alcohol.”
However, as they explained, while modern wineries use cultivated S. cerevisiae, ancient wine production likely relied on natural fermentation. Under those conditions, it’s unlikely that S. cerevisiae rarely colonized grape skins, which means it’s also unlikely that our wine-drinking ancestors used fresh grapes for alcohol fermentation. This led the team to explore what they might have used instead. Turns out, it was probably the “humble raisin.”
In a previous study, the team reported that researchers found S. cerevisiae to be abundant on raisins, making it a promising vehicle for wine production.
They put this theory to the test by collecting grapes and drying them for 28 days to make raisins, some in incubators, some in the sun, and some in a mix of both. Then, they soaked the raisins in water and stored them at room temperature for two weeks, taking three samples from each type of dried raisin. And they found that old-school is indeed best.
According to the team, the sun-dried raisins soaked in water produced the best wines, adding that “all three samples of sun-dried raisins in water fermented and yielded significantly higher ethanol concentrations.” Only one of the incubation-dried raisin samples fermented, and only two of the combination incubation- and sun-dried raisins fermented as well. They noted that their results suggest that “long before Jesus supposedly did so, ancient peoples may have figured out how to turn water into wine” using only the sun.
The one question the team still has is how S. cerevisiae migrates from the environment into the raisins. They also explained that another limitation of their work was that they used a smaller production scale and harvested the grapes outside the typical “raisin-producing regions.” Still, they believe their research provides a strong foundation for future studies.
“We aim to uncover the molecular mechanism behind this interaction between microbial flora and microorganisms that reside in various fruits, including grapes,” Wataru Hashimoto, the research team leader, added. “Through natural fermentation, we also hope to develop new food products and prevent food loss.”
And sorry, but as Hashimoto explained, you likely can’t replicate this process at home. “Note that this only works with naturally sun-dried raisins that are untreated,” he said. “Most store-bought raisins have an oil coating which prevents fermentation from taking place.”
Modern wines that still use the ancient “raisin method”
Long before stainless steel tanks and controlled fermentations, ancient winemakers depended on the sun to dry their grapes — and today, some of the world’s most loved wines still use versions of that same method. Known in Italy as appassimento, this traditional approach involves drying harvested grapes on straw mats or racks to concentrate their sugars and flavors prior to fermentation. The result: richer, more intense wines with naturally higher alcohol levels and complex flavor profiles.
Where you’ll see it today
- Amarone della Valpolicella (Italy): A robust, full-bodied red
- Recioto della Valpolicella (Italy): A dessert wine made from the same dried grapes as Amarone
- Straw wines (Italy, Greece, France, South Africa): Honeyed, aromatic wines made by drying grapes on straw mats — one of the earliest documented winemaking traditions
What to try
If the ancient raisin-fermentation method in the Kyoto study intrigues you, look for bottles labeled Amarone, Recioto, Passito, Vin Santo, or Straw Wine. These modern styles offer a delicious glimpse into how dried grapes can transform a wine — showcasing a technique that connects today’s winemakers with the earliest chapters of wine history.
