Researchers in China report that upcycling grape pomace – the skins, seeds and stems left from winemaking – could benefit both environmental sustainability and human health, thanks to its rich content of antioxidants, fibre and other bioactive compounds.
The findings were published in Food Chemistry X.
The researchers said a circular-economy approach could help manage grape pomace, reducing environmental pollution while creating new value-added products.
Uses of grape pomace
Grape pomace contains natural pigments, phenolic compounds, dietary fibre and polyunsaturated fatty acids.
Researchers noted it is a rich source of polyphenols, flavonoids, proanthocyanidins and minerals such as potassium, iron and zinc, making it a promising ingredient for health supplements and cosmetics.
Terminology
Antioxidants: Substances that protect cells from damage caused by unstable molecules known as free radicals. They help reduce oxidative stress in the body.
Phenolic compounds: Plant chemicals found in grape skins, seeds and stems. They include polyphenols and flavonoids, and are linked to antioxidant, anti-inflammatory and heart-protective effects.
Polyphenols: A major category of plant antioxidants found in grape pomace, known for supporting heart health and reducing inflammation.
Bioactive compounds: Naturally occurring compounds in foods that have health-promoting functions beyond basic nutrition – such as antioxidants, vitamins, minerals and plant chemicals.
Free radical scavenging capabilities: A property of antioxidants that allows them to neutralise free radicals, reducing cell damage and supporting overall health.
Anthocyanins: Natural red, purple and blue pigments found in grape skins. They act as antioxidants and are widely used as natural colourants in foods.
Flavonoids: A diverse group of plant compounds within the polyphenol family. They have strong antioxidant and anti-inflammatory properties and contribute to the colour and taste of grapes.
Proanthocyanidins: A class of powerful antioxidants found in grape seeds and skins. They are associated with cardiovascular benefits, anti-inflammatory effects and protection against oxidative stress.
Additionally, red grape skins contain 51–56% fibre by weight, while white skins contain 17–28%. The study noted that dietary fibre supports digestion and may lower the risk of chronic diseases by improving antioxidant activity and reducing cardiovascular and diabetes risk.
“Dietary fibre can enhance digestive efficiency and promote digestion due to its physical properties. Some fibre compounds can also combine with phenolic substances to produce antioxidant dietary fibre, thus possessing stronger free radical scavenging capabilities,” they wrote.
“Studies also point out that its consuming also has positive effects on reducing the incidence of cardiovascular diseases, and diabetes.”
Grape pomace also provides pectin, widely used as a gelling, emulsifying and stabilising agent in foods and pharmaceuticals. Due to its strong film-forming ability, pectin is used in edible coatings that extend shelf life.
The pomace also provides trace minerals such as potassium, zinc and iron, and grape seeds contribute oil rich in vitamin E, unsaturated fatty acids and antioxidant compounds.
Red grape pomace additionally contains anthocyanins, natural antioxidant pigments used as colourants in the food industry.
Potential as natural additives
With rising demand for natural additives, grape pomace extracts are increasingly explored as antioxidants, preservatives and colour stabilisers in functional foods.
Studies show they can extend the shelf life of meat products and improve the functional properties of dairy.
How grape pomace is applied in foods
Grape pomace can extend the shelf life of pork burgers and chicken meatballs, as well as provide additional functional benefits to dairy.
Dietary fibre in grape pomace also improves the sensory quality and texture of food, while offering potential gut health benefits.
- Research indicates that a 0.06% w/w usage level (0.06g grape pomace for every 100g pork burger) increased colour stability and reduced lipid oxidation.
- For beef burgers, 0.5, 1, 1.5 & 2 % w/w can improve fibre content and be used as a natural alternative to butylated hydroxytoluene – a synthetic antioxidant used to prevent rancidity and enhance texture.
- A 2–10% w/w usage level in orange and apple juices improved fibre content and antifungal activity.
- For yoghurts, 1% free or microencapsulated w/w enhanced antioxidant activity and increased gel strength.
Grape pomace is also used in commercially available supplements targeting cardiovascular health, antioxidant support and general wellness.
However, researchers acknowledged that there are barriers to large-scale upcycling of grape pomace.
Overcoming challenges
Researchers observed that social acceptance of upcycled products remains low, and transporting and preserving fresh pomace is costly.
Localised processing facilities could reduce costs, but technical challenges persist, including the need for more efficient extraction methods and better recycling of residues.
“Developing value-added use of waste such as grape pomace is very complex as it requires a high level of involvement by everyone, including consumers and policy makers,” said researchers.
Most value-added technologies developed in recent years have yet to be implemented at scale. Economically, the procurement and transport of grape pomace from vineyards to processing plants remain expensive, and preservation methods – needed to prevent the material from decomposing – further add to costs.
“Therefore, establishing value-added industries in each region that produce large quantities of grape pomace is an effective means of cost saving. Another reality is that the impact of processing costs, final product prices and consumer purchasing propensity can play a crucial role,” the researchers said.
Despite progress in extracting and purifying bioactive compounds, technical limitations still hinder the full conversion of pomace into high-value products. These challenges include identifying efficient extraction techniques, managing residual waste, and ensuring environmental sustainability and consumer acceptance.
In the short term, researchers suggest focusing on cleaner production processes, waste reduction and by-product recovery, while developing innovative products such as functional foods over the longer term.
Source: Food Chemistry X
DOI: https://doi.org/10.1016/j.fochx.2024.101845
“The high-value and sustainable utilization of grape pomace: A review”
Authors: Changsen Wang, Yilin You et al.
