Drying kinetics and stability of fatty acids in grape pomace seeds under mild thermal conditions

Grape pomace, a significant by-product of the wine industry, is rich in health-promoting compounds, including polyunsaturated fatty acids, dietary fiber, and polyphenols, and holds strong potential for use in functional foods and nutraceuticals. This study investigates the effects of low-temperature convective drying at 40°C on the drying behavior and fatty acid composition of grape seeds from ten Vitis vinifera L. cultivars. To model the drying process, six thin-layer drying models were applied. Among them, the Logarithmic model provided the best fit for most cultivars, showing excellent agreement between predicted and experimental drying curves. Effective moisture diffusivity values varied considerably among cultivars, reflecting differences in pomace structure and seed composition. Fatty acid analysis via gas chromatography revealed that polyunsaturated fatty acids-particularly linoleic acid-were the predominant lipid class in fresh grape seeds. After drying, a moderate reduction in polyunsaturated fatty acids was observed, accompanied by a corresponding increase in saturated fatty acids. Despite these changes, certain cultivars, such as Prokupac and Merlot, retained favorable nutritional profiles. The results support the application of mild drying protocols to preserve the functional quality of grape seeds while improving energy efficiency. This research contributes to the sustainable valorization of grape pomace and highlights its potential applications, such as functional oil ingredients, antioxidants in skincare, and encapsulated nutraceutical formulations.