Abstract
Although starch granules of roots and tubers were, in general, more resistant to the action of amylase than those of cereals, taro starch granules were highly susceptible and starch granules of banana, gingko and chestnuts were rather resistant to the action of pancreatin comparing with those of the normal corn. We also examined relative susceptibility to pancreatin of starch granules of 13 cultivars of legumes ( Vicia faba, Pisuna sativum var. arvense, Phaseolus vulgaris, Vigna sesquipedalis, Vigna angularis and Dolichos lablab) . These starch granules were, in general, less susceptible to the enzyme action than those of the normal corn . Starch contents of starchy legumes, soybeans and peanuts were 35-40, 0.8-1 .4 and 5.1% (on wet weight basis), respectively. The starch content of mung bean cotyledon decreased rapidly after 2-4 days germination. Decrease in starch content was confirmed by observation under a scanning electron microscope (SEM) of the dissected cotyledon of mung beans with or without germination. In the cotyledon of ungerminated mung beans many lumps of amyloplasts were observed and several starch granules with smooth surfaces were embedded in amorphous cementing materials in a cell . With the progress of germination the cementing materials disappeared and starch granules decreased in number. After 4 days of germination, although most starch granules had smooth surfaces, some granules had rough surfaces and some of them showed a hole at the end of the major axis . However, patterns of enzymatic erosion of the starch granules visible in the dissected endosperm of normal corn following the early germination period were seldom observed in the case of the cotyledon of germinating mung bean. By SEM observation starchy legumes and peanuts as same as mung bean seldom showed pattern of enzymatic erosion of starch granules in the dissected endosperm of normal corn. Approximately 50% of either potato or banana starch granules ingested by rats fed diets containing the starch granules as the main carbohydrate disappeared in rat bodies with making corrections for starches in feces and in contents of the gastrointestinal tracts. The intestinal enlargement caused by indigested starch granules was mainly due to hyperplasia. By SEM observation starch granules isolated from the digestive tracts of rats fed each one of diets con taining starch granules of banana, potato and Chinese yam (round-type) as the main carbohydrate showed typical patterns of the enzymatic attack, probably those of α-amylase attack, on their surface layers and inner portions. SEM observations of the cross-section of a grain of feces of rats fed each one of diets containing starch granules of banana, potato and Chinese yam (round type) revealed that damage of starch granules could be observed without the tedious procedure separating starch granules from feces.
