Deacetylated chitin used as adsorbent in production of clarified pineapple syrup

Abstract

A study of clarification of pineapple wastes syrup by a combined process of membrane ultrafiltration (UF), ion exchange and adsorption techniques using partially deacetylated chitin (PDC) as adsorbent material was conducted. Chitin from Black Tiger shrimp shell was used after undergoing deproteination, demineralisation and deacetylation with different concentrations of sodium hydroxide (NaOH). The performance of cation resin (Dowex 88), anion resin (Dowex 66) and PDC as adsorbent material were evaluated. Effects of flow rate ranging from 10 to 50 ml min−1 on operation and regeneration of the resins were also investigated. Chitin yield was about 31·2% of the shrimp shells, corresponding to about 89% recovery of the total chitin content of the shells. When treated with 5%, 10%, 20% and 30% NaOH, the degree of deacetylation increased with increasing concentration of sodium hydroxide. In ion exchange process, cation resin removed more than 90% of K+, Mg2+ and Ca2+ from UF mill juice at a flow rate of 30 ml min−1. In adsorption process, anion resin (Dowex 66) had more colorant removed (94% T) from UF mill juice than PDC treated with 30% NaOH (84·4% T). The optimum flow rate for cation resin was 10 ml min−1 for both operation and regeneration while for PDC, 30 ml min−1 was optimum for operation and 10 ml min−1 for regeneration. The concentrated pineapple syrup was clear with a colour value of 70·2% and pH value of 4·96. The main reducing sugars after concentration were glucose, fructose and sucrose at 29·05, 15·72 and 18·62% (w/v), respectively. © 1998 SCI.