Studies on the Retention of Meat Color of Frozen Tuna-VI

Three varieties of packaging materials with different air permeabilities were examined for the retention of tuna meat color during frozen storage. These included laminated aluminum foil (cellophane-polyethylene-aluminum-polyethylene in the order of lamination from the top), cellophane-polyethylene laminate and polyethylene film. The effect of ice-glazing was also tested. 1. Tuna meat vacuum-packed in the aluminum foil discolored at 2°C at a very slower rate than that packed in polyethylene film (Fig. 1). 2. In storage at -10°C and -20°C, the surface portion of meat packed in polyethylene film discolored at the lowest rate, while the sample which was vacuum-packed in aluminum foil in raw state before storing discolored at the highest rate. The vacuum-packed sample of frozen meat was intermediate between the above two. However, the discoloration rates of the inner portion were about the same (Figs. 2 and 3). Also, the discoloration of meat vacuum-packed in cellophane-polyethylene laminate was comparable to those of meat vacuum-packed in aluminum foil (Fig. 4). 3. The rate of discoloration of the surface portion from ice glazed sample was higher than those packed in polyethylene film at -12°C and -20°C, while the rates were almost the same in the inner portion (Figs. 5 and 6). A very slight discoloration was noticed in the ice glazed sample stored at -35°C (Fig. 7).