# Valorization Pathway for Grape Pruning and Pomace Waste from the Wine Industry: Energy and Non-Energy Applications

## TL;DR

This study explores using grape waste from winemaking for energy and antioxidant purposes, showing vine prunings can be burned for energy and grape pomace can act as a natural antioxidant in oils.

## Contribution

The paper proposes a novel valorization pathway for grape pruning and pomace waste, demonstrating their dual use in energy and antioxidant applications.

## Key findings

- Vine prunings are suitable for direct combustion in energy applications.
- Grape pomace extract has high antioxidant capacity and can increase sunflower oil stability by up to 42.5%.
- Grape pomace contains significant levels of phenolics, flavonoids, and anthocyanins, with cyanidin and epicatechin being prominent compounds.

## Abstract

Wine is a popular beverage worldwide, and its consumption continues to rise, leading to waste, particularly from vine prunings and grape pomace. The aim of this study was to create a valorization pathway utilizing these waste materials. To achieve this, proximate analysis, chemical composition, ultimate analysis, thermogravimetric analysis (TGA), and other physicochemical parameters for both vine prunings and grape pomace were assessed. Based on the results, vine prunings were identified as suitable for direct combustion in energy applications, and grape pomace was found to be suitable as an antioxidant in vegetable oil. Grape pomace extract showed the following results through UV-vis spectroscopy: total phenolic content of 1688.10 mg GAE/100 g, total flavonoids of 1330.39 mg catechin/100 g, and total anthocyanins of 12.61 mg cyanidin-3-glucoside/100 mg. The antioxidant capacity was measured through various assays: FRAP yielded 2179.19 mg ascorbic acid/100 g; DPPH measured 1704.41 µmol Trolox/100 g; and ABTS showed 48,271.31 µmol Trolox/100 g. The ORAC results, as determined by fluorescence spectroscopy, were 53,694.93 µmol Trolox/100 g. HPLC profiling revealed cyanidin as the main anthocyanin (26.52 mg/L) and epicatechin as the most abundant flavonoid (214.29 mg/L). Finally, the antioxidant capacity of grape pomace in sunflower oil was evaluated using OSI. It increased the oil’s stability by up to 42.5%, positioning grape pomace extracts as a source of natural antioxidants in vegetable oils.