Fading of muscle color by heat processing fall chum salmon

The reason of more fading color of fall chum salmon (Oncorhynchus keta) muscle than that of sockeye salmon (Oncorhynchus nerka) by heat processing was investigated. Fading was attributed to the following phenomenons:(1) Decrease in Hunter's chromatic a as well as b values was more pronounced in chum salmon than in sockeye salmon against the same decrease in carotenoid content. (2) Hunter a value as well as b value of salt-soluble protein+stroma protein fractions of fall chum salmon muscle decreased more than that of the sockeye salmon by the heating process.(3) Sensitivity of human eyes to color changes are differed by difference of a value. Thus, chum salmon muscle whose a value is originally less than sockeye salmon tends to exhibit an apparent fading compared to sockeye salmon.