The degrees of surface cracking of KML and CHN were similar and much larger than those of SPT. This implies that SPT kernels were less susceptible to surface crack formation. This may be due to the fact that SPT is a glutinous/waxy rice (low amylose content,
5.12%) but KML and CHN are non-glutinous rice (medium and high amylose contents, 16.17% and 30.35%, respectively). The hydrated tissue of SPT is more flexible/elastic than that of KML and CHN, as SPT contains a higher quantity of large branching molecules like amylopectin . Such a flexible structure could better compensate for the moisture-gradient cracking stress and the vacuuming/ pressurizing forces. In addition, SPT kernels are much more porous (being opaque) than KML and CHN kernels (being transparent) . Water can easily penetrate into the interior of SPT kernels, and therefore, a lower moisture gradient was formed within the SPT kernels, leading to reduced cracking stress. On the other hand, the non-glutinous KML and CHN rice grains contain similar degrees of porosity and amylose content, demonstrating a similar surface crack formation.