Effect of chitosan type on protein and water recovery efficiency from surimi wash water treated with chitosan–alginate complexes

Previous research has shown that soluble protein recovery by chitosan (Chi) complexes with polyanions such as alginate (Alg) is more effective than using chitosan alone. In this study, Chi–Alg complexes were used to recover soluble proteins from surimi wash water (SWW) slightly acidified to pH 6. Six Chi samples differing in molecular weight (MW) and degree of deacetylation (DD) were used at 20, 40 and 100 mg/L SWW Chi–Alg complexes prepared with a Chi:Alg mixing ratio previously optimized (MR = 0.2). FTIR analysis of the solids recovered revealed the three characteristic amide bands observed in the same region for untreated SWW confirming protein adsorption by Chi–Alg. The superior effectiveness of Chi complexes was confirmed but differences among chitosan types could not be correlated to MW and DD. Experimental Chi samples with 94%, 93%, 75% and 93% DD and 22, 47, 225 and 3404 × 103 Da, respectively, showed 73–76% protein adsorption while a commercial chitosan sample with 84% DD and 3832 × 103 Da had 74–83% protein adsorption. An experimental chitosan, SY-1000 with 94% DD and 1.5 × 106 Da, showed the highest protein adsorption (79–86%) and turbidity reduction (85–92%) when used at 20 mg/L SWW.