Analysis of Metmyoglobin Formation Rates in Frozen Tuna Meat during Frozen Storage

抄録

Formation of metmyoglobin (metMb) in frozen tuna meat stored at -90, -60, -40, -30, -20, and -10°C for approximately 6 months was investigated. The reaction rate of metMB formation was estimated from a linear plot of ln ([M_∞ . M_t] /[M_∞ . M_o]) and storage time (t) for each storage temperature (T_s) (M_∞, M_t, and M_o are metMb contents at times t = t_∞, t, and 0, respectively). When M_∞ was assumed to be 100%, the rate of metMb formation followed the first-order reaction only during the early stage of storage period. MetMb formation, however obeyed the first-order reaction for all test temperatures even during long-term storage when M_∞ was assumed to be dependent on storage temperature (M_∞(Ts)). A discontinuity was observed in the temperature dependence of M_∞(T_s) at storage temperature range between -60 and -40°C, which was attributed to the glass transition of protein system. On the other hand, the temperature dependence of metMb formation did not show a significant change over all storage temperatures.