Discoloration Kinetics of Clarified Apple Juice Treated with Lewatit® S 4528 Adsorbent Resin During Processing

摘要

The present work studies the adsorption of colored compounds in apple juice with a Lewatit® resin S 4528. The sorption equilibrium through the adsorption isotherms for 20, 35, and 50 °C was studied. The absorbance at 420 nm was used to measure the concentration of colored compounds, which permits correlating the residual concentration with the adsorbed concentration, proving that the data matched reasonably well according to the Langmuir and Freundlich models. Also, the efficiency of the adsorption process was studied for different resin/juice mass ratios at different temperatures, from which it was observed that there was an improvement in efficiency as the resin content increased, while the increase in temperature was not so important in the process. The adsorption kinetics at 35 °C for different resin/juice mass ratios was also studied. The kinetic model developed by Ibarz was used, concluding that the data matched this model reasonably well. The adsorption kinetic constant was always higher than the desorption kinetic constant, which indicates that the adsorption stage predominates the desorption stage. The adsorption kinetic constant shows a decreasing tendency with the raise in the resin/juice ratio, and the desorption kinetic constant shows an increasing tendency. The variation of the CIELab color parameters (L*, a*, and b*) with the adsorption time was studied, obtaining results that match the kinetic adsorption model proposed.