[en] The solid gelatin as the model protein, was irradiated with ⁶⁰Co gamma rays in air at room temperature at dose rates of 6.0 x 10⁴ to 1.3 x 10⁵ rad/h. The irradiated solid gelatin was dissolved in distilled water or metal ion (Cu²⁺ as CuSO₄ of Fe²⁺ as FeSO₄) solution at about 80 C. and held at 30 C. for 1 h. Then, the gelatin hydrosol was cooled at a rate of 0.2 C./min and the setting point measured. The heat energy required to associated cross-links of the gelatin hydrosol was calculated using the setting point given by the equation of Eldridge and Ferry. The changes in setting point of irradiated gelatin with and without metal ions (Cu²⁺ and Fe²⁺) were studied with 3-10% gelatin and by the irradiation of 0, 10⁵, 10⁶, and 10⁷ rad