A new drying method for winemaking waste, developed by researchers from UrFU as part of an international team, makes it possible to convert up to a quarter of the berry mass left after wine production into health-boosting preparations. The findings were published in the journal Waste and Biomass Valorization.
Grape pomace—a mixture of skins, stems, and seeds—accounts for 20 to 25 percent of the original raw material, according to experts at the Ural Federal University named after the first President of Russia B. N. Yeltsin (UrFU). Currently, this byproduct is used to produce food and textile dyes, livestock feed additives, or certain alcoholic beverages like grappa.
However, these applications fail to tap into the full potential of grape pomace as a source of beneficial compounds for humans, which exhibit antioxidant, antimicrobial, and vessel-strengthening properties.
“The challenge with this raw material is that fresh grape pomace has high moisture content (50–60 percent water by weight), causing it to quickly sour and become prone to microbial spoilage, making it unsuitable for long storage or efficient processing. So the first and most critical step in pomace processing is removing water—dehydration—without destroying valuable compounds through heat,” explained one of the study’s authors, Zakir Hassan, a research engineer at the Scientific, Educational, and Innovation Center for Chemical and Pharmaceutical Technologies at UrFU.
In collaboration with specialists from Bangladesh, the university researchers identified a temperature “sweet spot” that extends the shelf life of grape pomace while only minimally affecting the levels of beneficial phenolic compounds. These include, for example, invigorating caffeic acid and catechins, which strengthen blood vessels and protect tissues from free radicals.
“If you dry grape pomace in an oven, you need to maintain a temperature between 45 and 60 degrees Celsius. Higher drying temperatures cause the breakdown of phenolic compounds, though they have a less pronounced effect on flavonoids—substances that are also beneficial to the human body and give grapes their color,” Zakir Hassan noted.
For their experiments, the scientists used equipment common in industrial settings and professional kitchens—a convection oven, whose design ensures even heating of the contents. Due to the widespread availability of such ovens, the researchers believe that converting grape pomace into useful ingredients for food and dietary supplements can be implemented on a broad scale.
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