Studies on Influence of Rays upon Film-Packing-IV

In the preceding report1), we described that “sakura-dembu” could not be protected from discoloration by packing with any of transparent films having different permerbility to oxy-gen and ultraviolet rays, The present report deals with the protective effects of cellophane of different colors as the wrapping materials on the discoloration of “sakura-dembu”. Each sample packed with polyethylene-laminated cellophan of the same kind was over-wrapped with colored cellophane. The cellophane materials used were red, orange, yellow, green and colorless. The wrapped samples were subjected to storage for one month at room temperature under natural conditions. The smallest “color difference values” were determined with the samples wrapped with red cellophane. The samples wrapped with green cellophane also gave low values. On the other hand, those with orange cellophane gave much larger values and those with yellow cellophane nearly the same values as the control materials with plain cellophane, showing no protective effect. Plotting a against b values at varying storage periods shows that there is little change of b in any of the samples. Other samples double-wrapped in the same way as in the foregoing experiments were irradiated for 1.5 hours with ultraviolet rays from a fade-meter. The order and the tendency of discoloration of the samples wrapped with cellophane of different colors were the same as those obtained under natural conditions. These results indicate that discoloration of such foodstuffs as “sakura-dembu” may be satisfactorily evalua-ted by a short-time irradiation with ultraviolet rays instead of by a long-term storage under natural conditions.