Heat treatment of scallop adductor muscle using superheated steam

Scallop (Patinopecten yessoensis) adductor muscles were heated using superheated steam (150 and 200 degrees C), boiling (98 degrees C), and normal steaming (95 degrees C). The amounts of amino acids, water-soluble peptides, and nucleotides, expressed as extractive nitrogen in scallop products, are very important elements of quality and taste. After 15-min heating of scallop muscles with normal steaming and boiling, respective losses of 50% and 64% of the extractive nitrogen were observed. However, most extractive nitrogen (> 86%) remained in the scallop muscles treated with superheated steam at 150 and 200 degrees C. Protective effects of superheated steam against elution loss of nitrogen compounds were also observed in amino acid analyses of the heated products. The scallop-muscle surface temperature during treatment with superheated steam increased more quickly than that with normal steaming and boiling. The rapid water loss and the surface protein denaturation engendered formation of a 30-mum-thick film covering the surface, which prevented extractive nitrogen loss from internal tissues. Superheated steam treatment at 200 degrees C caused browning, surface shrinkage, and 47% weight loss. In marked contrast, the appearance and the weight loss of sample treated at 150 degrees C were almost the same as those of normal steaming and boiling-treated samples. These results suggested that superheated steaming at 150 degrees C is an optimal heat treatment of scallop adductor muscles.