Functional Properties of Pork Liver Protein Fractions

The functional (emulsifying, gelling and foaming) properties of liver protein fractions as well as their molecular weight distribution and surface hydrophobicity were investigated and compared to commercial proteins. Two protein fractions were characterized: water soluble (WSLP) and WSLP combined with salt soluble liver proteins (W + SSLP). The effect of salt concentrations was also investigated (0, 1.8 and 3.4 % NaCl). Both WSLP and W + SSLP displayed good emulsifying properties and foam stability. However, their gelling properties were rather poor. An increase in salt concentration decreased the emulsifying properties of WSLP while the effect on W + SSLP was less pronounced. Addition of 1.8 % NaCl increased foaming ability of WSLP and W + SSLP while foam stability was not affected. Further increase of NaCl (3.4 %) decreased both foaming ability and foam stability and is probably attributed to refolding of the protein molecules because of the higher level of hydrophobic groups with 3.4 % NaCl. Gel forming ability of WSLP and W + SSLP containing 0 % was higher compared to high salt concentrations. However, higher salt concentrations shifted onset gelation temperature of WSLP and W + SSLP to lower temperatures probably due to partial unfolding of the proteins as indicated by an increase of the surface hydrophobicity.