Scientists can repurpose millions of tons of winemaking waste — here’s how

So, what do wineries do with all those unnecessary leftovers? Even with all the liquid extracted, many wineries and businesses are now discovering that grapes have more to offer beyond just being used for making a good glass of wine.

Let’s look at how winemaking waste is being put to new uses and how some innovative approaches shape sustainability initiatives within the industry.

Grape stems

Grape stems, also known as grape stalks, are significant winemaking byproducts resulting from the destemming  process and typically constitute between 2.5 and 7.5 percent of the total weight of the grapes.

Stems are removed before fermentation and are frequently used to produce compost or feed livestock as they are rich in nutrients. However, a significant portion of them ultimately gets discarded in open fields, leading to environmental issues.

However, according to a 2012 study published in the scientific journal LWT – Food Science and Technology, stems display great potential for commercial use in the cosmetic, food, and pharmaceutical industries due to their high phenolic content.

Known for their antioxidant and anti-inflammatory properties, phenolic extracts from stems have shown positive results when included in cosmetic products, promoting skin health, battling aging, and shielding the skin against environmental stressors.

Supportive evidence from a study published in the peer-reviewed International Journal of Molecular Sciences last year underscores that beauty products with extracts protect the skin from UV damage, boost collagen production, and enhance skin elasticity.

The same research emphasizes that these products have demonstrated great results in soothing irritated skin and reducing redness.

Additionally, rather than disposing of grape stems, scientists from Japan’s Shinshu University suggest using them in the pharmaceutical industry due to their significant anti-cancer activity against tumor cells.

A similar 2014 study from the journal Toxicology Letters shows they are highly effective against colon, breast, renal, and thyroid cancer cells.

Grape pomace

Also referred to as grape marc, pomace is the leftover material after pressed grapes. It comprises grape skins, seeds, and occasionally some stems.

Pomace can lead to pollution of the surface and groundwater as pesticides and fertilizers applied to the grapes may leak into the ground. Because of its low pH level, it can also result in soil contamination, causing the soil to become more acidic.

“Large amounts of grape waste may be detrimental to the environment,” says Changmou Xu, Ph.D., a research associate professor at the University of Nebraska-Lincoln, in a press release.

Xu emphasized that when left in landfills, pomace can even contribute to spreading diseases because it can attract flies and pests.

However, scientists and companies exploring innovative methods to repurpose pomace have lately incorporated it in various food products, such as bread, cereal, pasta, cheese, and ice cream, and even added it to meat and seafood.

One example is Vine to Bar, a fresh company whose chocolate-covered almonds and flavored bars are uplifted with the WellVine™ Coastal Chardonnay Marc.

This nutrient-dense superfood product, which promotes gut and cardiovascular health and normal blood sugar levels, can be used in foods and dietary supplements.

In the world of cosmetics, a novel British skincare brand called Pelegrims recently used polyphenols from waste grape seeds, skins, and stems to create a beauty line rich in antioxidants.

“Sustainability is hugely important to us, so using waste products from the wine-making process and harnessing the powerful grape extracts are at the core of our brand and our future research,” said Alex Verier, Pelegrims co-founder.

“We’re looking forward to documenting our product journey in the years ahead.”

Researchers are also increasingly focused on finding ways to extract beneficial elements from the pomace for use in fuel alcohol and biofuel energy production, as well as biosurfactant production.

Traditional ways of removing pomace include distilling it to make other types of alcohol, such as grappa, or recycling it as fertilizer or animal feed.

Wine lees

Apart from stalks and pomace, wine lees are another byproduct of winemaking, representing approximately 13 percent of the total wine production.

Mainly consisting of dead yeast cells, lees are found on the bottom of the fermentation tank and are racked off and discarded after the winemaking.

More than 2.5 million tons of lees are produced each year around the world. But, given how lees are considered a soil pollutant, wineries face significant expenses in managing their disposal.

Despite being considered waste, lees are naturally rich in phenolic compounds, offering valuable antioxidant and biological benefits. Recent research shows they can improve the flavor, color, taste, and texture of ice cream, yogurt, and burgers.

A study led by Tuncay Gumus, PhD, head of the Department of Food Engineering at Tekirdag Namik Kemal University, Turkey, recently showed how using lees as a coloring agent can improve the texture and flavor of jelly.

When used as a colorant, wine lees not only enhance jellies with higher antioxidant properties due to their rich anthocyanin and phenolic content but are also cheaper than their commercial alternatives.

“By repurposing lees as a natural colorant and functional ingredient in jelly, we not only prevent environmental harm but also add value to what would otherwise be waste, aligning with principles of sustainability and waste reduction,” Gulce Bedis Kaynarca, PhD, research assistant, and study co-author told IE in an interview.

Kaynarca is optimistic that the research will pave the way to other potential uses for wine lees promoting environmental sustainability.

“In our future research, we plan to explore the use of wine lees in different foods where colorants are commonly used, such as in the beverage and confectionery industries, as well as in products targeted at children,” says Kaynarca.

“Due to their high phenolic content and antioxidant activity, wine lees may be incorporated into the formulation of dietary supplements and healthful snack foods with potential cardioprotective and anti-cancer properties,” she adds.

Aside from food coloring, lees can additionally be used as a valuable source of ingredients for nutraceuticals and pharmaceuticals, according to recent research from chemical engineers at Monash University.

Polyphenols extracted from lees protect against the development of cancers, cardiovascular disease, diabetes, osteoporosis, and neurodegenerative diseases and could prevent several chronic diseases.

Another possible use for wine lees is as a substrate for microalgae cultivation, according to a 2023 study published in the journal Waste.

“This transformation of lees into a beneficial product reflects a responsible approach to both environmental protection and innovative food production,” Kaynarca concludes.