Large sized frozen yellowfin tuna and southern bluefin tuna in dressed form (decapitated and gutted) were thawed by microwave (915 MHz) irradiation. Temperature rise of the tuna during thawing was measured. Quality of the tuna meat before and after thawing was compared with each other using objective quality index such as degree of discoloration (met-myoglobin ratio), freshness (K₁ value) and taste cornponent (K₂ value).
Results are as follows :
(1) Both frozen tunas were thawed fairly well within as short time as 30 min without any partial over heating.
(2) No changes in met-myoglobin ratio, K₁ and K₂ values were observed in the cases of yellow fin tuna. Slight discoloration, however, occurred in southern bluefin tuna meat during microwave thawing. This problem has been left unsolved.