Graduate Thesis Or Dissertation

Surimi wash water treatment by chitosan-alginate complexes : effect of molecular weight and degree of deacetylation of chitosan and nutritional evaluation of solids recovered by the treatment

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  • Soluble surimi wash water (SWW) proteins could be recovered using chitosan (Chi) complexed with alginate (Chi-Alg) generating co-products for feed formulations. Chi with a degree of deacetylation (DD) of 84% complexed with Alg at a mixing ratio (MR) of 0.2 was used to study Chi-Alg concentration and treatment time protein recovery effects. Insoluble SWW solids were removed by centrifugation and the supernatant was then adjusted to pH 6. Flocculation at 20°C using Chi-Alg at 20, 40, 100 and 150 mg/L SWW was aided by 5 mm agitation and holding for 30 mm, 1h and 24h. Concentration had an effect between low (20 and 40 mg/L) and high (100 and 150 mg/L) levels. Time had an effect between 30 min and 1h but not between 1 and 24 h. Turbidity reduction was affected only by concentration. 100 mg Chi-Alg/L SWW for 1 h achieved 83% protein adsorption and 97% turbidity reduction while lower concentrations yielding higher adsorption required longer times. Fourier Transform Infrared (FTIR) analysis of untreated and Chi-Alg treated SWW solids confirmed protein adsorption. Amide band areas normalized against a common 3005-2880 cm⁻¹ region confirmed the high protein recovery by 100 mg Chi-Alg/L SWW. Six Chi samples differing in molecular weight (MW) and degree of deacetylation (DD) were tested to recover soluble SWW solids using 20, 40, and 100 mg Chi-Alg/L SWW (0.2 MR, 1h). High (94%, 93%) and low (75%) DD chitosan had lower protein adsorption (73-75%) when compared to the intermediate (84%) DD chitosan (74-83%). Intermediate DD and high MW Chi seemed to perform better; however, SY-1000 with 94% DD did not follow this trend (79-86% protein adsorption, 85-92% turbidity reduction). Insoluble SWW (P1) and soluble solids (P2) recovered using 150 mg Chi- Alg/L SWW contained 61.4 and 73.1% protein, respectively. Rat diets formulated with 10% protein substitution by P1 and 10% and 15% by P2 had acceptability and protein efficiency ratios (PER) as high as the casein control with no deleterious effects. Rat diets with 100% P2 protein substitution showed higher PER and net protein ratio than the casein control with no deleterious effects. Protein recovered from SWW using Chi-Alg has the potential to be used in commercial feed formulations.
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