From Vine to Value: Upcycling Wine Grapes

When winemakers press grapes, they're after the juice. But what happens to the skins, seeds, and stems that make up nearly 30% of the harvest?

At Terra Madre Americas in Sacramento in September 2025, two UC Davis researchers revealed how this "waste" is becoming the wine industry's next frontier of innovation.

The Scale of the Opportunity

California's wine industry generates hundreds of thousands of tons of grape pomace annually. Traditionally, this material heads to compost piles or animal feed operations. But recent research shows these leftovers contain concentrated antioxidants, dietary fiber, and bioactive compounds that could benefit human health and nutrition.

Ned Spang, Ph.D, Associate Professor in Food Science and Technology, has made food waste his specialty. His research optimizes water, energy, and food resource systems, developing new products and business models from materials currently going to waste. "We're essentially throwing away some of the most nutritious parts of the grape," he explained during the panel.

Joining him was Selina Wang, Ph.D, Associate Professor of Cooperative Extension. Her work spans food quality, processing innovation, and sustainability, including finding ways to transform byproducts into valuable ingredients. 

Together, they made a compelling case that grape pomace isn't waste waiting for disposal. It's an untapped resource waiting for the right application.

What's Inside Grape Pomace?

Wine grape skins and seeds are packed with polyphenols, the same compounds found in red wine.

These include resveratrol, which has been linked with cardiovascular health; anthocyanins, the powerful antioxidants that give grapes their color; proanthocyanidins, which support immune function and cellular health; and dietary fiber, which plays key roles in digestive health.

The challenge isn't nutritional value, it's finding practical, scalable applications that work for both producers and consumers.

From Vineyard to Kitchen

Wang's expertise in food processing and quality made her the perfect guide for emerging applications that transform grape pomace into valuable products. 

Grape flour can be milled from dried pomace and incorporated into baked goods, adding fiber, color, and subtle fruity notes. Early adopters are using it in crackers, cookies, and artisan breads.

Dietary supplements extract concentrated antioxidants for capsules and powders, creating a premium ingredient from what was once destined for compost.

Natural food colorants derived from anthocyanins offer a plant-based alternative to synthetic dyes, appealing to clean-label manufacturers.

Chocolate and confections are incorporating grape pomace powder to boost nutrition while delivering exceptional flavor, with products already on store shelves.

The Circular Economy in Action

What makes grape upcycling particularly compelling is its alignment with circular economy principles. Wineries already collect and process grape pomace; the infrastructure is in place. The innovation lies in redirecting this material toward human consumption rather than disposal.

Spang's research on linked resource systems reveals benefits throughout the value chain. Wineries can generate new revenue streams from byproducts. Food manufacturers access sustainable, locally sourced ingredients. Consumers gain nutritious options with compelling sustainability stories and the environment benefits from reduced waste and transportation needs

Challenges and Solutions

Despite its promise, grape upcycling faces hurdles. Food safety regulations require careful handling and processing to prevent contamination. Variability in grape varieties, growing conditions, and winemaking processes means pomace composition isn't standardized.

Cost remains a consideration. Drying, milling, and processing grape pomace requires investment, and products must compete price-wise with established ingredients.

Yet solutions are emerging. Partnerships between wineries and food processors can distribute costs and expertise. Regional cooperatives could aggregate pomace from multiple producers, creating the volume needed for efficient processing. And growing consumer interest in sustainable, nutrient-dense foods is creating market pull.

Beyond the Bottle

Wang emphasized that successful upcycling requires thinking beyond waste reduction to product innovation. Her lab specializes in identifying chemical markers important for food quality and nutrition, exactly the approach needed to transform pomace from problem to ingredient.

"We're not just using grape pomace because it's available," she noted. "We're using it because it brings something valuable, flavor, nutrition, color, that consumers want."

This shift in mindset transforms pomace from a disposal problem into an ingredient opportunity. It's the difference between tolerating grape flour in a recipe and seeking it out for its unique properties.

The Taste Test

During the Terra Madre Americas demonstration, attendees sampled chocolate made from grape pomace powder, a product from Vine to Bar, a brand already available to consumers. The chocolate showcased how upcycled grape ingredients can elevate familiar products rather than compromise them.

The experience revealed an important insight. When done well, upcycled products don't taste like "wine waste," they deliver on flavor while offering nutritional benefits. Vine to Bar's chocolate demonstrates that grape pomace brings genuine value to the final product, not just a sustainability story.

This successful application proves that upcycling can enhance products rather than merely repurposing waste, and that consumers are already embracing these innovations on store shelves.

Looking Forward

The wine industry has long celebrated terroir as the way place and process shape flavor. Upcycling extends this concept, honoring the entire grape and the land that produced it.

As climate change pressures agriculture and consumers demand more sustainable food systems, innovations like grape upcycling offer practical paths forward. They prove that environmental responsibility and culinary excellence are complementary goals.

For California's wine country, where sustainability initiatives are increasingly central to regional identity, grape upcycling represents an opportunity to lead by example. The grapes that give us wine can give us so much more.

Join the Movement

Want to support upcycled food innovations? Look for products featuring the Upcycled Certified mark when you shop, try brands like Vine to Bar that are transforming food waste into delicious products, and ask your local wineries what they're doing with their grape pomace.

Interested in learning more about sustainable food systems research? Visit the Robert Mondavi Institute for Wine and Food Science to explore cutting-edge research and educational programs. Terra Madre Americas returns to Sacramento in 2027. Visit Slow Food USA for updates on this celebration of good, clean, and fair food for all.

Kaylianne Jordan is a junior transfer student studying Viticulture and Enology at UC Davis. She has a background in culinary arts and a passion for sustainable farming and enjoys exploring the connections between agriculture, winemaking, and community. Outside of college, she loves trying out new recipes, discovering local food spot.