Effects of frozen storage temperature on the quality and oxidative stability of bigeye tuna flesh after light salting

Abstract

SUMMARYEffects of frozen storage temperature on the quality and oxidative stability of lightly salted tuna were investigated. The bright and vivid colour became totally brown after 4 weeks at −20 °C and 8 weeks at −30 °C, where the a*/b* value decreased from 1.35 to 0.38 and 0.58, respectively. Discoloration and lipid oxidation occurred concurrently in lightly salted tuna flesh, and it was speculated that the oxidation of oxymyoglobin to metmyoglobin exacerbated lipid oxidation and vice versa. Storage at −40 °C or lower temperatures effectively suppressed the discoloration and maintained the high water‐holding capacity and unique textural properties of lightly salted flesh. It was attributed to the reduction in the conformational changes and particularly hydrophobic interactions among proteins, protecting the myoglobin from oxidative damages during frozen storage. Considering the quality maintenance and energy savings, storage at −40 °C was appropriate for lightly salted tuna flesh.