DHret was not detected for low amylose containing flours; this can be attributed to the structure of amylopectin in starch. Zhu et al. (2010) also did not detect any DHret for waxy rice flours.
Würsch and Gumy (1994) reported that starches did not show any retrogradation enthalpy when exterior chain length of amylopectin was less than 11. Medium and high amylose containing flours showed DHret between 1.2–3.7 J/g and 2.6–3.3 J/g.
DHret indicates the energy required to melt the double helices formed during gel storage (Ratnayake, Hoover, Shahidi, Perera, & Jane,
2001).
%R for medium and high amylose containing flours was observed between 11.8–42.8% and 40.1–42.8%, respectively. The retrogradation tendency of flours may depend on the rigidity and size of starch granules and lipids present.
The heating cycle applied in DSC might have increased the ability of rice storage protein to bind to amylose and/or amylopectin, thus influencing retrogradation