Effect of heating on residual carbon monoxide content in co-treated tuna and myoglobin

Carbon monoxide (CO) can be used by food manufacturers to retain the red color of meat or dark fish prior to vacuum packaging or in the modified atmosphere packaging. Yellowfin tuna steak (c. 1.5 cm) was treated with CO gas, then packaged in a vacuum bag and heated at a constant temperature ranging from 50 to 100C for 30 min. A myoglobin (Mb) solution was prepared from tuna dark muscle and purged with CO gas for comparison. The released CO concentration and the residual CO in the tuna flesh or Mb solution were measured by gas chromatography. The higher level of CO concentration in the vacuum bag from CO-treated tuna was found for conditions with temperatures above 80C. The content of residual CO in the CO-treated tuna steaks after heating was much higher than that in untreated flesh. Regardless of the temperature of heating, a ratio of 58-82% CO was released from Mb solution after heating. This suggested that MbCO was not completely dissociated by heating at temperatures ranging from 50 to 100C.