Food-scientific investigations on so-called crystalline taro occurring in the child-corm of an early-maturing Colocasia antiquorum named cv. Ishikawa-wase.

Abstract

So-called crystalline taro (Suisho-imo in Japanese) occurs often in the child-corm of an early-maturing Colocasia antiquorum named cv. Ishikawa-wase. The corm looks semi-transparent at the lower part close to the binding site with the parent-corm when cutlongitudinally into halves. The tissue cells of the lower part (showing semi-transparency)were proven to be alive by causing plasmolysis in a hypertonic solution. Observations undermicroscope and naked-eye after staining with iodine-iodide solution indicated that starchgrains were not contained in the cells. According to the quantitative analyses, starch waspresent in very smaller amounts, and water in larger amounts in the lower part than in theupper part (not showing semi-transparency). The hardness of the corm was investigatedafter steaming, and the lower part was much softer than the upper part. This accorded withthe absence of starch grains in the lower part. Thus, crystalline taro proved to be inferior tohealthy taro from the viewpoint of nutrition and palatability. The method of discriminatingcrystalline taro from healthy taro without tissue destruction was devised by utilizing thedifference in specific gravity between the lower and upper parts based on the absence orpresence of starch grains. When the corms of crystalline taro were immersed in water, theyassumed the perpendicular posture, taking the lower part upwards, but those of healthy taroassumed the horizontal posture in water. The observations on taro during growing at thefields and after harvest indicated that when the leaves and stems were unsatisfactorily grown, crystalline taro often occurred.