Studies on the Density of Starch Granules Potato

Abstract

We report the results of some measurements of the density of potato starch granules. The density was determined as the weight of one starch granule divided by its volume. The weight of one granule was determined as follows: (1) the granule size was kept constant through the use of standard sieves; (2) the number of granules in Microslides (by Vitoro Dynamics Inc.) was counted under a microscope; (3) the glucose value was determined by the phenolsulphuric acid method; (4) the starch value was calculated by multiplying the glucose value by 0.9; and (5) the starch value was divided by the number of starch granules. The arithmetic average of these data indicates the weight of one potato starch granule.
Next, the volume of one granule (moisture content: ca. 12%) was calculated using an elipsoidal equation. The diameter (length and breadth) of a granule was determined by means of photomicrographic measurement. The number of glucose residues in one granule was determined as the starch value of one starch granule divided by 2.69×10^-16μg (M) of a glucose residue molecule. The average number of glucose residues in 1nm³ was determined as the number of glucose residues in one starch granule divided by the volume of one starch granule; and the following results were obtained.
(1) In the growth stage of potato starch granules, the density of the granules fell from about 2.0g/cm³ to about 1.1g/cm³.
(2) The starch granules were classified throughout the whole distribution and divided into four classes on the basis of the number of glucose residues in 1nm³ of one starch granule.