Improvement of functional properties of cod frame protein hydrolysates using ultrafiltration membranes

Enzymic hydrolysis was applied for the efficient recovery of the protein so urces from the fish processing by-product, cod frame. The enzyme used for t he hydrolysis was crude proteinase extracted from tuna pyloric caeca. The r esultant hydrolysate, cod frame protein hydrolysate (CFPH), was separated b ased on the molecular weight of the peptides in the hydrolysate and several functional properties were examined, including physicochemical properties (emulsifying and foaming property) and bioactivities (antioxidative and ang iotensin I converting enzyme (ACE) inhibitory activity) to determine its po tential functions. CFPH was processed through a series of ultrafiltration ( UF) membranes with molecular weight cut-off(MWCO) of 30, 10, 5 and 3 kDA, a nd four types of permeates including 30-K (permeate from 30 kDA), 10-K (per meate from 10 kDA), 5-K (permeate from 5 kDA) and 3-K hydrolysate (permeate from 3 kDA) were obtained. 10- and 30-K hydrolysates showed excellent emul sion properties and whippability. The 10-K hydrolysate showed high antioxid ative activity, while the 3-K hydrolysate had excellent ACE inhibitory acti vity. In terms of all functional properties tested, the fractionated hydrol ysates were superior to the original non-separated hydrolysate. These resul ts suggested that separating hydrolysate enhanced several functional proper ties. (C) 2000 Elsevier Science Ltd. All rights reserved.