Commercial Potato Starch Standards Cannot Be Used in Place of Cassava Starch Standards when Measuring the Starch Content of Cassava Samples

In this study, the shapes, diameters, and molecular weights of cassava and potato starch granules are compared. The cassava starch granules generally exhibit a polyhedral and truncated shape, while the potato starch granules exhibit a regular, elliptical shape. The diameters of the cassava starch granules are mostly between 0 and 20 µm, while the diameters of the potato starch granules are mostly between 7 and 40 µm. The average diameter of the cassava starch granules is over 20 µm smaller than that of the potato starch granules. The molecular weights of amylose and amylopectin from cassava and potato starch are also quite different. All of these differences directly or indirectly lead to differences in the ability of cassava and potato starch to bind with iodine, ultimately resulting in a different standard curve for use in the measurement of starch content. Finally, when the starch content of the cassava samples is measured by a dual‐wavelength method (using potato starch as a standard), the measured amylose contents are 5.31–29.59% higher than the corresponding theoretical values, the amylopectin contents are 15–209.9% lower than the corresponding theoretical values, and the final measured total starch contents are 8.29–115.85% lower than the corresponding theoretical values.