The chemical composition and some physico‐chemical characteristics of the flour obtained from eight different banana varieties are presented. The flour was prepared by freeze‐drying a homogenate of green banana pulp. Amylose, starch, dietary fiber, protein, ash, moisture and lipid contents were determined. Viscosity and gelatinization of starch were also investigated. Banana flour is rich in starch granules. Peak temperature of gelatinization varied from 68 to 76 °C according to the variety. All of them showed an increase in viscosity during cooling but the variety Ouro colatina showed more stability during shearing and cooling. Chemical composition of the flour also varied according to the variety. The range obtained were 61—76.5% starch, 19—23% amylose, 2.5—3.3% protein, 4—6% moisture, 0.3—0.8% lipids, 2.6—3.5% ashes, and 6—15.5% total fiber. Considering that the flour production is easier and faster than the isolation of the starch, it would be not only more practical but also less expensive to use the flour instead.

In this study the relationship between the enzymatic susceptibility and the size of the corn and cassava starch granules was studied. The starch granules were separated by size and classified according to their average diameter in: a) larger than 16 urn: b) between 15 and 10 um and c) smaller than 10 um. The starch granules of various sizes were hydrolyzed by bacterial alpha‐amylase and fungal amyloglucosidase. The results showed a relationship between the enzymatic susceptibility and the size of the starch granules: smaller size of the starch granules resulted in a higher percentage of hydrolysis. A basic difference in the mode of action of enzymes on small and large granules was observed. Enzymatic attack on the large granules was characterized by considerable surface corrosion, mainly at the radial axis. For small granules, the enzymatic action occurred on the surface of the granules and was characterized by an erosion with solubilization of the granules. Chemical and physical analysis of the starches suggested that hydrolysis should occur mainly at the amorphous areas of the granules.

Normal and waxy corn starches were isolated, adjusted to different levels of moisture and heated at 100°C for 16h. The heat treated starches were hydrolysed with α‐amylase and amyloglucosidase. The starch samples were studied by determining their water‐binding capacity, pasting properties, X‐ray diffraction and by optical and scanning electron microscopy. The results showed that the heat‐moisture treatment produced an increase in the degree of crystallinity of normal and waxy corn starches at the level of 18% moisture. This result, in conjunction with a significant decrease in the enzymatic susceptibility, suggested a rearrangement of the starch molecules with strengthening of the linkages within the granules. On the other hand, the heat‐moisture treatment caused a rupture with further rearrangment of linkages within the granules for normal and waxy corn starches adjusted to the 27% moisture level. This produced a certain degree of starch degradation increasing the accessible regions of the granule to amylolysis.