MODIFICATION OF OVALBUMIN WITH GLUCOSE-6-PHOSPHATE BY AMINO-CARBONYL REACTION - IMPROVEMENT OF PROTEIN HEAT-STABILITY AND EMULSIFYING ACTIVITY

Ovalbumin (OVA) was modified with glucose (Glu) and glucose B-phosphate (G6P) through the amino-carbonyl reaction (Maillard reaction), and heat-induced aggregation and emulsifying activity of the modified proteins were investigated. G6P reacted with the free amino groups in a similar manner to Glu; about 70-80% of the total amino groups were blocked by the reaction at 50 degrees C, and 65% relative humidity for 3 days. However, the reaction with G6P induced protein polymerization and brown-color development more strongly than that of Glu. OVA modified with G6P was much more acidic than either native OVA or the Glu-modified OVA, and it was highly soluble and quite resistant to heat-induced aggregation, i.e., its high-concentration solution (5%) was still completely soluble and transparent even after being heated at 100 degrees C for 10 min. Furthermore, OVA emulsifying activity was increased about 5-fold by the modification with G6P.