## 3 Experimental
### Materials
The kinetic assays were performed in 25 mL Erlenmeyer flasks, with 5 mL of the liquid phase separated from winery wastes and further diluted and 3 g of resins at an initial pH 4.0, at 25 \({}^{\circ}\)C for up to 3 h. The content of each flask was filtered trough a 0.45 \(\upmu\)m membrane filter and the liquid phase was analyzed. The pseudo-first-order rate equation of [PERSON] is generally described by equation (2), and assumes that the rate of solute uptake is proportional to the gradient in saturation concentration. \[\frac{dq_{t}}{dt}=k_{t}\left(q_{e}-q_{t}\right) \tag{2}\]  
where _q_t and _q_e are the amount of phenol adsorbed (mg/g) at contact time \(t\) (min) and at equilibrium, _k_\({}_{I}\) is the pseudo-first-order rate constant (min\({}^{-1}\)). Integration and linearization leads to:  
\[\log(q_{e}-q_{t})=\log q_{e}-\frac{k_{t}}{2.303}t \tag{3}\]  
The pseudo-second order kinetic model is represented by:  
\[\frac{dq_{t}}{dt}=k_{z}\left(q_{e}-q_{t}\right)^{2} \tag{4}\]  
where t is the contact time, _q_t and _q_e are the concentrations of phenolics adsorbed (expressed as mg/g) at the considered time and at the equilibrium respectively, _k_\({}_{2}\) is the pseudo-second order kinetic parameter. Integration and linearization results in:  
\[\frac{t}{q_{t}}=\frac{1}{k_{z}q_{e}^{\ 2}}+\frac{t}{q_{e}} \tag{5}\]  
_Washing._ Distilled water was used to remove unadsorbed compounds susceptible of reducing purity of the extracts desorbed in further stages. Washing was performed in two stages with distilled water at a water:resin ratio of 3 (g:g) in an orbital shaker (175 rpm) at 25 \({}^{\circ}\)C for 20 min. _Desorption._ Ethanol/water mixtures were selected on the basis of availability, suitability for food uses, and the reported cleanup capability. Optimization of the desorption conditions to produce a purified antioxidant extract was addressed by applying a central composite factorial design. The independent variables were temperature (\({}^{\circ}\)C), and the ethanol content (%, v/v), coded as:\[\mathrm{T}=\frac{\mathrm{Temperature-35}}{10} \tag{6}\]  
\[\mathrm{E}=\frac{\mathrm{Ethanol\,concentration-68}}{20} \tag{7}\]  
The dependent variables or objective functions were expressed according to the general expression of a second order polynomial equation (equation 8). The phenolic desorption yield (Y1, %), the sugars desorption yield (Y2, %), the total phenolic content (Y3, g GAE/g extract), the total sugar content (Y4, g d-glucose/g extract) and the radical scavenging activity (Y5, mM Trolox) were expressed as a function of linear, interaction, and second-order terms involving the normalized, dimensionless variables T and E:  
\[\mathrm{Y_{i}=a_{0}+a_{T^{\prime}}T+a_{E}E+a_{TE}T\cdot E+a_{TT^{\prime}}T^{2}+a _{EE}E^{2}} \tag{8}\]  
where Yi(i = 1-5) are the dependent variables, T and E are the dimensionless, normalized, independent variables, and a0, aT, aE, aT, aT and aEE are regression coefficientes calculated from experimental data. During elution the resin, saturated at conditions previously selected, was contacted with the ethanol:water solution at a moist resin to ethanol ratio 1:3 (g:mL) (resin moisture is approximately 65%). The desorbed extract was analyzed for phenolic and sugar content and for radical scavenging activity. The resin regeneration procedure consisted on leaving the resin overnight in 1 M NaOH and further washing with deionized water.