Researchers from the Institute of Food Science Research (CIAL) in Madrid, Spain tested ways to characterize food byproducts using two-dimensional liquid chromatography (LC×LC). Their findings were published in the Journal of Chromatography A (1).
In modern society, almost every industrial activity has had to be refined and improved to minimize their environmental impact and reduce their negative effects on the planet. The food and agricultural industries are no exception. Currently, very large quantities of residues and byproducts related to food productions are being created which not only are deleterious for the environment but also imply significant economic losses due to necessary treatment and disposal. While some food byproducts have diverse uses, they typically have generally low-value applications, such as energy production through incineration or being integrated as feeds. However, approaches are being made to find high-added value applications for available byproducts.
Grape pomace, one of the main byproducts generated by the winery industry, is made up of solid materials—such as skins, pulp, and seeds—left over after the creation of wine or juice (2). 200 kg of grape pomace are generated per 1000 kg of processed grapes. In Uruguay, the flagship strain of grape is Vitis vinifera L. cv Tannat, which corresponds to 27% of all wine grapes harvested in the region (in terms of area). In 2021–2022, the average production of this wine was 20 million liters, with this variety being distinguished for having exceptionally high levels of polyphenolic compounds, especially anthocyanins and tannins, which partially remain in the grape pomace after the vinification process. These substances have potential bioactivity and are particularly highlighted for being capable of preventing oxidative brain damage associated with aging, as well as downregulating gene expression linked to inflammatory pathways.
Pressed grape pomace, seeds and skins. Winemaking background. | Image Credit: © aquatarkus - stock.adobe.com
Producing an effective valorization of available byproducts requires efficient and environmentally-respectful advanced extraction techniques that can increase the recovery of the compounds in question. Supercritical fluid extraction (SFE) has been reported as a useful technique to selectively isolate bioactive compounds from different byproducts; one must consider that the technique is suitable for low-polarity components due to its use of carbon dioxide (which has a very low polarity) as a supercritical fluid. Pressurized liquid extraction (PLE) is another technique that allows solvents to be maintained in their liquid state, thus allowing target compounds to be extracted.
In this study, PLE was explored to obtain bioactive compounds from Tannat grape pomace. After optimization, the best extraction conditions implied the use of 55% ethanol as a solvent at 141 ºC for 20 min. To correlate the observed bioactivities with the extracts’ chemical compositions, an original LCxLC method coupled to mass spectrometry (MS) was created to separate and identify components present in the extract.
The LCxLC analysis of the optimum extract separated over 70 different analytes. Proanthocyanidins were among the most abundant phenolic compounds, although others, such as flavonols and anthocyanins, were also identified. In addition, there were 38 different structures tentatively identified. Overall, the experiments shown demonstrated PLE’s usefulness in valorizing important agrifood-related by-products, such as Tannat grape pomance.
(1) Rajchman, M.; Montero, L.; Aicardo, A.; Radi, R.; Herrero, M. Green Extraction of Bioactives from Vitis vinifera L. cv. Tannat Pomace and Chemical Characterization by Comprehensive Two-Dimensional Liquid Chromatography (LC × LC). J. Chromatogr. A 2025, 1754, 466040. DOI: https://doi.org/10.1016/j.chroma.2025.466030
(2) Crowe, A. The Pomace Predicament. WineMaker 2025. https://winemakermag.com/article/678-the-pomace-predicament (accessed 2025-6-11)
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