Transforming winemaking waste: grape pomace as a sustainable source of bioactive compounds

Abstract

Grapevines (Vitis vinifera L.) are plants of great economic importance, with over 80% of grape production dedicated to wine production, yielding more than 258 million hectoliters annually [1]. However, the winemaking process generates a substantial amount of by-products, primarily grape pomace (GP), wine lees, and wastewater, posing serious environmental and economic challenges [2]. Efficient strategies for the sustainable valorisation of these residues are therefore essential. Recent research highlights the potential of grape pomace (GP), which has traditionally been considered as a mere waste, as a valuable source of bioactive compounds [3-5]. With up to 70% of the total phenolic content of grapes retained post-vinification [6], GP valorisation aligns with circular economy principles, presenting innovative and sustainable solutions.

This study investigated the phenolic composition and antioxidant capacity of GP from different grape varieties from the Rhône Valley area of France, including red (Alicante, Syrah, Mourvèdre, Grenache Noir), white (Vermentino, Grenache Blanc, Roussanne, Clairette), and rosé (Grenache Rosé) varieties. Total polyphenol content (TPC) was measured using the Folin-Ciocalteu method, while phenolic profiling—covering phenolic acids, flavonoids (flavan-3-ols, anthocyanins, flavonols, flavones, etc.), and stilbenes—was conducted using HPLC-UV-QqQ. Antioxidant capacity was evaluated through DPPH, ABTS, FRAP, and ORAC assays.

The results revealed significant phenolic retention in GP post-vinification, ranging from 15–35 GAE/g DW in fermented (red) GP and 20–25 GAE/g DW in non-fermented (white, rosé) GP. Fermented GP seeds, particularly from Syrah and Alicante varieties, displayed the highest phenolic content, rich in flavan-3-ol monomers and procyanidins, and exhibited superior antioxidant activity compared to GP skins. Non-fermented GP also demonstrated a notable phenolic profile, with elevated flavan-3-ol and flavonol levels and antioxidant capacities comparable to red GP varieties. Correlations between phenolic composition and antioxidant activity were explored to better understand the functional properties of bioactive compounds.

These findings underscore the potential of GP as a low-cost by-product that can be transformed into high-value polyphenolic extracts for applications in nutraceutical, cosmetic, and food industries.

References

[1] International Organisation of Vine and Wine. State of the World Vine and Wine Sector in 2023, OIV, 2024.

[2] Karastergiou, A.; Gancel, A.-L.; Jourdes, M.; Teissedre, P.-L. Valorization of Grape Pomace: A Review of Phenolic Composition, Bioactivity, and Therapeutic Potential. Antioxidants 2024, 13(9), 1131.

[3] Onache, P. A.; Geana, E.-I.; Ciucure, C. T.; Florea, A.; Sumedrea, D. I.; Ionete, R. E.; Tit, O. Bioactive Phytochemical Composition of Grape Pomace Resulted from Different White and Red Grape Cultivars. Separations 2022, 9, 395.

[4] Caponio, G. R.; Minervini, F.; Tamma, G.; Gambacorta, G.; De Angelis, M. Promising Application of Grape Pomace and Its Agri-Food Valorization: Source of Bioactive Molecules with Beneficial Effects. Sustainability 2023, 15, 9075.

[5] Chedea, V. S.; Macovei, S. O.; Bocsan, I. C.; Măgureanu, D. C.; Levai, A. M.; Buzoianu, A. D.; Pop, R. M. Grape Pomace Polyphenols as a Source of Compounds for Management of Oxidative Stress and Inflammation—A Possible Alternative for Non-Steroidal Anti-Inflammatory Drugs? Molecules 2022, 27, 6826.

[6] Milinčić, D. D.; Stanisavljević, N. S.; Kostić, A. Ž.; Soković Bajić, S.; Kojić, M. O.; Gašić, U. M.; Barać, M. B.; Stanojević, S. P.; Tešić, Ž. L.; Pešić, M. B. Phenolic Compounds and Biopotential of Grape Pomace Extracts from Prokupac Red Grape Variety. LWT 2021, 138, 110739.