EFFECT OF CHITOSAN ADDITION ON THE PROPERTIES OF GELATIN GELS

Chitosans with different molecular weightes (A : 200,000 approximately 300,000; B : 40,000 approximately 60,000; C : 10,000 approximately 30,000; D : ca. 2,000) were added to 2 approximately 5% gelatin solution in 2% aq. ascorbic or malic acid solution to form gels. The changes of physical properties of gels by adding the chitosans of 0.25 approximately 1.0% concentrations to gelatin solutions were investigated. The results obtained were as follows : (1) The breaking stress-strain values of the gels varied with the gelatin concentration and with the kinds of chitosan added. By an addition of chitosan D, the smallest molecular weight one, both the breaking strees and the strain values increased, which suggested that tough gels were formed by gelatin-chitosan interaction. (2) The evaluation of viscoelastic properties by creep measurement for the 2% gelatin-ascorbic acid gels showed the increase of elastic modulus with chitosan A addition and the decrease of viscous modulus with chitosan B, C and D additions. (3) The measurement of released water by syneresis showed that the larger a molecular weight of chitosan added, the smaller the amounts of released water. The amount of released water decreased remarkably in the 5 % gelatin-ascorbic acid gel by the addition of 1% chitosan A, where the water release was only 1%.