Effect of polyethylene package on the metmyoglobin reductase activity and color of tuna muscle during low temperature storage

Bluefin tuna (Thunnus thynnus) meat, wrapped with or without polyethylene f ilm, was stored at 4 degrees C and relative humidity of 100%. Decrease in H unter's 'a' and increase in 'L' were observed in both samples during 120 h storage. Metmyoglobin (metMb) reductase activity of both samples decreased, while the metMb increased with the duration of storage. The nicotinamide a denine dinucleotide (NADH) of tuna meat increased during the first 56-80 h of storage, but decreased again during the further storage. Although the ni cotinamide adenine dinucleotide phosphate (NADPH) of both wrapped and unwra pped samples decreased with the duration of storage, the total amount of NA DH and NADPH seemed to remain at a constant level during the first 80 h sto rage and then significantly decreased during further storage. The metMb red uctase is an important factor affecting the accumulation of metMb of refrig erated tuna.