Physicochemical characterization of isolated nanocrystals in starch and isolated rice starch: A new perspective

In this work, isolated rice starch (IRS) ( Oryza sativa cv. large grains) from the macro to the nanoscale is investigated. IRS contains P, Mg, K, Mn, Na and Ca as well as traces of Fe, Si, Al, and Zn. The internal structure of IRS consists of nanometric rings with a thickness of 50–70 nm containing nanocrystals isolated by an acidic method (INCs). The X-ray pattern in starch is generated by nanocrystals with orthorhombic crystal structure confirmed by transmission electron microscopy images (3–6 nm and a length of 15–25 nm). After gelatinization this pattern appears amorphous. IR and Raman of IRS and isolated nanocrystals show that the spectrum of starch is the superposition of their individual components. TEM-energy dispersive spectroscopy showed that the INCs are composed of C, O, and H, and contain traces of Ca, P, Mg, and Na. • Rice starch contains nanorings with nanocrystals and void volume. • Rice starch contains nanocrystals with orthorhombic crystal structure. • Isolated nanocrystals are formed by pyroglucan units and contain minerals. • Gelatinization is an order to disorder thermal transition governed mainly by nanocrystals.