Abstract

Grape pomace is a winery by-product whose valorisation requires stabilisation strategies to preserve quality during storage. This study assessed gamma irradiation (gamma-IR) as a non-thermal treatment for two commercial grape pomace matrices, unfermented 'Sauvignon blanc' (SBP) and fermented 'Malbec' pomaces. Samples were exposed to 0-2000 Gy and analysed after 1 and 30 days for phenolic stability, mineral composition, and mineral-phenolic relationships. Effects depended on dose, matrix, and storage. Doses of 500-1000 Gy preserved phenolics with minor mineral changes, whereas higher doses increased phenolic losses. At day 30, non-coloured phenolics in SBP varied by less than 16% from day-1 levels at 500-1000 Gy but decreased by 31% at 2000 Gy. DPPH antioxidant capacity declined by 39-52% in SBP and 8-49% in Malbec pomace. In SBP, the initial bacterial reduction was not sustained after 30 days of refrigerated storage. Exploratory correlations suggested mineral-phenolic associations. Overall, gamma-IR shows promise as a matrix-specific pretreatment.