ADSORPTION OF DARK COLORED COMPOUNDS IN APPLE JUICE – EFFECTS OF INITIAL SOLUBLE SOLID CONCENTRATION ON ADSORPTION KINETICS AND MECHANISM
Adsorption of dark colored compounds onto adsorbent resin was studied for different adsorbent resin concentrations (1.5, 2.0, 3.0, 5.0, 10.0, 15.0 g resin/L apple juice) and different °Brix ratios of apple juice (10, 20, 30 °Brix). The equilibrium data obtained fitted well to Langmuir isotherm. The maximum adsorption capacity was found 0.124 1/g resin at 30C for apple juice having a °Brix ratio of 10. The adsorption of dark colored compounds from apple juice onto adsorbent resin followed pseudo-second-order kinetic model. The adsorption rate constants decreased as the °Brix ratio of apple juice increased. As it was confirmed by Bangham's equation, the rate-limiting step was intraparticle diffusion. This study showed that using adsorbent resin to improve color had no effect on organic acid and sugar composition of apple juice. PRACTICAL APPLICATIONS
Browning during processing and storage adversely affects the commercial acceptability of apple juice concentrate. Adsorption is considered as a viable process to improve apple juice color. The present study shows the adsorption behavior, kinetics and mechanism of dark colored compounds in apple juice. From a practical application point of view, initial soluble solid content of apple juice is considered as an important parameter that should be taken under control to improve the adsorption efficiency. After the adsorption process, the level of main constituents such as sugar and organic acids remain constant so this adsorption process appears to be effective for apple juice process.
Document Type: Research Article
Publication date: February 1, 2011