Softening of the Cultured Yellow-tail Bone in Association with Collagen Gelatinization by a Retort Treatment

The conditions for the softening of cultured yellow-tail bone to eatable hardness by a retort treatment were examined. For the softening, heating temperature and time required were over 120°C and 40 min respectively. Collagen, one of the main constituents in the bone, was found to be gelatinized during the above treatment and collagen content decreased substantially, while Ca and P in the bone remained constant. Furthermore, Ca and P uniformly distributed in the retort treated-bone matrix at similar density to that in the raw material. Therefore, the bone softening seems to be mostly caused by gelatinization of collagen. It was found that the bone of cultured yellow-tail was rich in lipid, especially in DHA and EPA, and the total lipid content did not decrease by the retort treatment. Thus the yellow-tail bone could be utilized as a new source of functional lipid components as well as a Ca source.