Lipophilization of herring protamine to improve antimicrobial and emulsification properties

The antimicrobial and emulsifying properties of lipophilized protamine were investigated as a function of fatty acid type, number of fatty acids and pH. Herring protamine was modified with palmitic chloride and myristic chloride through the Schotten-Baumann reaction, to give peptides having 3 (M 3:1) or 5 (M 5:1) myristic acids or 5 palmitic acids (P 5:1) per protamine molecule. The attachment ratio was verified through acid hydrolysis and gas chromatography (GC).; The attachment of fatty acids significantly increased the surface hydrophobicity and decreased interfacial tension at both pH 5.2 and pH 7.2. M 5:1 had the greatest hydrophobicity followed by M 3:1 and P 5:1, however, hydrophobicity was lower for each species at pH 7.2. Conversely, P 5:1 had the greatest interfacial tension followed by M 3:1 and M 5:1; all being lower at pH 7.2. Native protamine showed no significant drop in interfacial tension as compared to the buffer system.; Native protamine destabilized emulsions whereas the incorporation of fatty acids onto the protamine imparted emulsification properties. All modified forms produced emulsion droplets of similar size at each pH, however, droplet size was greater at pH 5.2 than 7.2. Emulsification activity (EA) was greatest for M 5:1, followed by P 5:1 and M 3:1, however, EA was greater at pH 7.2 than 5.2. Emulsion stability (ES) was similar for all modified forms at pH 5.2, whereas at pH 7.2, stability decreased significantly. M 5:1 had the greatest ES followed by M 3:1 and then P 5:1. (Abstract shortened by UMI.)...