The Utilization of By-Product from Surimi Industry :Laboratory Scale Production of Spray Dried Fish Protein Hydrolysate

Abstract

Heads and guts of threadfin bream, by-products from surimi industry, were ground and dried to 6.85% moisture content. Dried fish parts containing 49.92% protein, 9.32% fat and 31.12% ash (dry basis), was used as raw material for the study of fish protein hydrolysate (FPH) production. Pretreatment conditions of dried fish parts were compared among 3 groups : control (soaked in distilled water), heating in autoclave and soaking in alkali. Conditions of enzyme hydrolysis were investigated. The results showed that alkali treatment (NaOH at pH 8.5, 90 min. 10°C) followed by enzyme hydrolysis (alcalase activity 2.4 AU/gm, 0.075 ml per 100 gm dried fish) 150 min at 60°C, produced FPH with the highest emulsifying capacity. Enzyme activities were inhibited by heating the mixture to 100°C for 15 min. The aqueous solution of FPH was separated after being centrifuged. Drying conditions by means of spray dryer were studied. It was found that good quality FPH can be made from the following spray dry conditions : 160°C inlet air temperature, 5 kg/cm² air pressure for rotary atomizer and 300 ml/hr feed rate. The resulted spray dried FPH has 3% moisture content and 81% protein (TN × 6.25). Comparison of FPH and sodium caseinate functional properties showed that water holding capacity, emulsion stability and gel strength of 3% FPH were higher than those of the control (no extra protein) and 3% Na-caseinate sausage. However, the fishy odor of FPH in the sausage could be detected by taste-panels. In order to maintain high quality, dried FPH was vacuum packed in aluminum foil/PE laminated bag to be kept away from humidity, O₂ and light.