Comparative Evaluation of Shade and Sun Drying of Grape Pomace: Mathematical Modeling, Biochemical Characterization, and LC–Orbitrap–MS Profiling of Bioactive Compounds

Grape pomace, a nutrient‐rich by‐product of winemaking, is highly perishable due to its high moisture content. This study aimed to evaluate the drying behavior of grape pomace under sun and shade drying, identify the best‐fitting drying models, and assess the impact on key bioactive compounds. Sun drying required 68 h, while shade drying required 168 h for drying of grape pomace. The drying rate declined over time in both methods. Among seven mathematical models tested, the approximation of diffusion model best described shade drying ( R 2 = 0.9915; RMSE = 0.0566; χ 2 = 0.0145), while the Midilli et al. model showed best fit for sun drying ( R 2 = 0.9987; RMSE = 0.0250; χ 2 = 0.0029). Biochemical analysis revealed significant degradation postdrying: total phenolics declined from 83.15 ± 0.75 mg GAE/100 g (fresh) to 27.04 ± 1.01 mg (shade) and 21.09 ± 0.43 mg (sun); antioxidant activity dropped from 87.2 ± 0.06% to 34.07 ± 0.04% (shade) and 23.52 ± 0.02% (sun). LC–HRMS profiling identified flavan‐3‐ols, hydroxybenzoic acids, hydroxycinnamic acids, flavonols, flavones, and anthocyanins across all samples. Total relative concentration decreased from 27,432.61 ± 225 mg/kg (fresh) to 18,952.19 ± 779 mg/kg (shade) and 13,543 ± 599 mg/kg (sun), indicating substantial degradation, with better retention under shade drying. Overall, sun drying is time‐efficient, while shade drying better preserves the bioactive integrity of grape pomace. The findings provide critical insights to inform the strategic selection of drying methods, tailored to specific end‐use objectives‐whether prioritizing process efficiency or the preservation and recovery of functional bioactive compounds.