PURPOSE: To obtain a pure starch suitable to impart advantages of a high amylose starch such as good gel strength to foods by extracting starch bearing plants having an amylose extender dull shrunken-1 genotype.

CONSTITUTION: The objective starch is obtained by, for example, wetgrinding starch bearing plants having an amylose extender dull shrunken-1 genotype (example: corn grain). A sol, after being prepared by mixing water and normally 1 to 20 wt.% starch extracted from starch bearing plants having an amylose extender dull shrunken-1 genotype, is added to foods and, by cooking the resulted compositions, thickened foods having superior gel strength are obtained.