Abstract
Disintegration of steamed root tissues was investigated using cultivars and breeding lines having various textures, and the contents of starch, pectic substances and calcium in the raw roots were analyzed. The steamed roots of cultivars and lines with high starch content showed a mealy texture and low degree of tissue disintegration. The 5 groups of roots, categorized by texture in reference to a standard cultivar (Kokei 14), were classified into 3 or 4 significantly different (p < 0.05) groups based on starch content. The disintegration-rate of steamed root tissue, expressed by the rate of weight decrease after agitation in water by shaking, was correlated with texture; textural differences could also be attributed to the degree of disintegration, particularly for roots with moderate starch content (16-22.5%). The disintegration-rate of steamed root tissue indicated a negative correlation (r=-0.403) with fresh weight Ca content per root, which could not account for the textural differences. The disintegration rate also showed a weak negative correlation (r=-0.214) with the content of chelating agent-soluble pectic fraction extracted from starch residue. In summary, the disintegration rate of steamed root tissues was associated with their texture, which largely depended on starch content; and the rate was equally related to Ca and starch contents via interaction with chelating agent-soluble pectic substances.
