The recovery of functional protein from fish waste

This research project is concerned with the recovery of Functional Fish Protein from fish filleting waste by an extraction method utilising sodium chloride solutions. It was found that the greatest amount of extracted protein could be obtained after one hour of extraction time using 4% NaCl as a solvent. The optimum solid-to-liquid ratio was 1:8 and the best particle size was found to be 0.04 cm diameter. The Silverson homogenizer was found to give a higher protein yield than other extraction apparatuses which utilise orbital or rotary motions. It was found that minced fish waste samples stored at -30°C for sixty days did not result in a noticeable deterioration in protein extractability values. Those values decreased by about 27% and 60% after seventy days storage at -15°C and 0°C respectively. The protein–saline extract was desalted and concentrated by means of an ultrafiltration process. The effect of protein concentration, temperature and pH of the feed stream on the flux rate were studied. It was found that the flux rate: (i) decreased as protein concentration rose; (ii) increased with increasing temperature of solution; (iii) did not change at basic pH, but decreased at acidic pH. The functional properties of the freeze-dried product were assessed. The characteristics of solubility, coagulation, foam and emulsification showed that Fish Protein Concentrate was suitable for use as a functional agent in food products.