Methods for determination of milt protein and ε-polylysine in food additive preparations and processed foods by capillary zone electrophoresis

A simple and rapid method using capillary zone electrophoresis (CZE) for the determination of milt protein (MP), which contains mainly protamine, and polylysine (PL) in food additive preparations and processed foods was developed. CZE separation was performed on poly(vinyl alcohol)coated capillaries at a column temperature of 20 degreesC with 120 mmol/L phosphate buffer (pH 2.5) as the running buffer. The influence of various components in food additive preparations on CZE analysis of MP and PL was examined. Egg white lysozyme, glycine, sodium acetate, glycerol, fumaric acid, calcium carbonate, dextrin, emulsifiers and sodium polyphosphate and pyrophosphate had no effect. No peak of protamine was detected in preparations containing metaphosphate. The analysis method for processed foods was composed of extraction with 4% formic acid, precipitation of macromolecular compounds with ethanol, concentration in a water bath and determination by CZE. The average recoveries were 108.4% for protamine sulfate (PS) in red bean sticky rice, and 81.3% for PL in white rice, 118% in egg sandwiches, and 115% in shiraae. The limits of detection of PS in red bean sticky rice and PL in white rice were both 50 ppm.