1971 Volume 18 Issue 4 Pages 22-25
(1) Iodine affinity (I. A.) values of 7 starch samples (each sample treated with petroleum benzine, treated with methanol, and untreated) were measured by means of the automatic amperometric titration method in a team project . Amylose contents of these samples were calculated from the I . A. values of methanol-extracted samples, on the basis of a standard I. A, value (-19) of amylose : the results obtained were 23-25% for 3 ordinary cereal starches, 19-20% for 3 tuber or root starches and 3 % for waxy corn starch.(2) The 7 starch samples were divided by the type of titration curve into two groups : 4 cereal starches and 3 tuber or root starches. The samples of the latter group have a refracting point in the sharply ascending straight part of titration curve .(3) Since the slopes of the sharply ascending straight line of titration curves differed with starch samples, the slope was corrected in such a manner that the slope for sample solution became identical with the slope for the blank solution . The I. A. values after the correction were only 0.1-0.4 higher than the uncorrected values .