Seven Fifty Daily - The Science of Grape Co-Fermentation

Researchers and winemakers weigh in on how the centuries-old practice of fermenting white and red grapes together affects a wine’s color, flavor, and texture

Nicole Rolet, the CEO of Provence winery Chêne Bleu, argues that even small additions of white grapes have an effect on a red wine’s structure and flavors. “Our Syrah is very similar to that of the northern Rhône. Nice aromas, good tannin and aging potential, but also a bit austere,” she says, hinting at her Syrah, Grenache and Roussanne blend, Héloïse. According to Rolet, co-fermenting Roussanne lends the wine a certain fleshiness and pleasant aromatics. 

Casassa’s research partly corroborates Rolet’s claims: “We found that the dilution effect occurs across the board with additions of [white grapes],” says Casassa. “But this is a dilution effect on color, not on flavor. Flavor is sometimes lifted by these additions, depending upon the variety. Viognier seems to work best, and I suspect this is because of the addition of Viognier’s terpenes to the red ferments.”

Following years of experiments, Rolet found that blending white and red wines after fermentation yielded significantly different results as the white variety’s aromas were “getting lost in the blend”—a claim that this time clashes with Casassa’s research. “We never found that co-fermentation actually results in better liquids than simply blending the finished wines,” says Casassa. “This applies both to red-red or red-white co-ferments … chemically and sensorially, the difference between co-fermenting and blending seems to be relatively minor.”’

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