Composition of grape pomace: Essential and toxic elements across different cultivars

Grape pomace, a major by-product of the wine industry, represents a promising source of minerals with potential applications in food and nutraceutical products. This study characterized the mineral composition of grape pomace obtained from different cultivar–locality combinations in three Slovak wine-producing regions and explored patterns of variability among macroelements, trace elements, and potentially toxic elements. Element concentrations were determined using flame atomic absorption spectrometry (FAAS), graphite furnace atomic absorption spectrometry (GFAAS) for cadmium and lead determination, UV–Vis spectrophotometry for phosphorus determination, and cold vapor atomic absorption spectrometry (CV-AAS) for direct mercury analysis. Potassium was the predominant macronutrient in all samples, while calcium, phosphorus, magnesium, and sodium exhibited variation among the analyzed samples. Among trace elements, iron, zinc, copper, chromium, and nickel showed the greatest variability, with elevated concentrations observed in several analyzed samples, particularly Dunaj and Sauvignon Blanc from Tajna. Potentially toxic elements generally occurred at relatively low concentrations. The results indicate that grape pomace represents a valuable source of essential minerals with potential for valorization in food applications.