Food Technology Research Center, Hiroshima Prefectural Technology Research Institute, Minami, Hiroshima 732-0816, Japan
We examined softening of cod and squid meat with freeze-thaw enzyme. Commercial protease for food processing was impregnated into the cod and squid meat under reduced pressure after freeze-thaw. Samples were removed from the enzyme solution and reacted at 10°C for 20 hours. The samples were heated at 95°C for 10 min before measuring the hardness. The hardness of cod and squid meat reached 5×104 N/m2 or less and their original shape did not change. The cod and squid meat, into which enzyme was infused, became substantially soft depending upon heating from 40°C to 60°C. SDS-PAGE revealed that their muscle proteins were decomposed by heating. The amount of free amino acid of the softening cod meat increased compared with that before processing. In particular, remarkable increase was observed in proteinogenic amino acid. This technique could be useful for softening fish and squid meat for elder persons and those under nursing care.