Improvement of Emulsifying and Antibacterial Properties of Salmine by the Maillard Reaction with Dextran

In order to improve the emulsifying and antibacterial properties of salmine (a protamine from salmon sperm), its conjugates with dextran (molecular weight 60, 000-90, 000) were prepared through the Maillard reaction above glass transition temperature (Tg). Development of brown color and formation of salmine-dextran conjugates were concomitantly accelerated at heating temperatures above Tg+30°C. The emulsifying activity of the conjugates became 4-5 times as high as that of salmine during the early stage of the Maillard reaction at 180-190°C, but decreased drastically at the advanced stage. The antibacterial activity of salmine was also increased by the conjugation with dextran. Even antibacterial activity against some species of Gram-negative bacteria was attained as a result of the conjugation. Potential use of salmine-dextran conjugates as bifunctional food additives is discussed.