Red Wine Lees Valorization for Phenolic Compounds Recovery and Characterization Using Resin Adsorption

Wine lees are a phenolic-rich winery by-product whose liquid fraction remains underexploited. This study investigated the direct recovery of phenolic compounds from the liquid fraction of red wine lees (LfWL) using the non-ionic Amberlite XAD-16 resin through batch and fixed-bed adsorption, followed by sequential desorption and LC-HRMS profiling. Batch adsorption experiments were conducted at resin dosages ranging from 20 to 120 g/L. The highest adsorption yield (89.9%) was achieved at 120 g/L, whereas the highest experimental adsorption capacity (123.5 mg SAE/g) was obtained at 20 g/L. Adsorption kinetics were better described by the pseudo-second-order model, whereas the non-linear Langmuir model provided the best equilibrium fit, with a model-estimated maximum adsorption capacity of 304.34 mg SAE/g. Phenolics adsorption was favored at the natural pH of the LfWL, while the thermodynamic analysis indicated an exothermic and thermodynamically favorable process. Two different fixed-bed columns were evaluated under continuous flow conditions. The configuration with larger dimensions (LFB-200) treated an undiluted LfWL, reaching an adsorption efficiency of 36.59% with a breakthrough profile extending beyond 1400 min. Sequential elution with water followed by a 50% (v/v) ethanol/water mixture resulted in desorption yields of 88.96% and 79.54% for the small and large columns, respectively. LC-HRMS enabled the putative annotation of 20 phenolic compounds and revealed compound and class-dependent elution profiles. These results support resin adsorption as a promising route for direct phenolic recovery from liquid wine lees fractions.