Starch can become swollen by heating the starch with an excess amount of water. The water-holding properties of starch is generally expressed as swelling power (SP) and water-soluble index (WSI) (Abegunde et al. 2013; Zhu and Wang 2014). Starch swelling is highly temperature dependent in that both SP and WSI tend to increase with a corresponding increase in temperature (Lawal and Adebowale 2005). High temperatures tend to disrupt the crystalline structure of the starch, which promotes hydrogen bonding between water molecules and amylose/amylopectin (Hoover 2001).
There is great diversity in SP and WSI among starches as reported by many studies (Zhu et al. 2011b; Abegunde et al. 2013; Zhu and Wang 2014). Differences in SP and WSI among starches reflect the variation in their water-holding capacities. The variation can be affected by many factors, including amylose and amylopectin properties (ratios, molecular weight, chain length, and others), the presence of minor components (lipids, phosphates), and the granular structure of starch (Beta et al. 2001; Li and Yeh 2001; Abegunde et al. 2013). Different sample pretreatments could also contribute to variations observed among various studies (Beta et al. 2001). A two-stage swelling pattern of some starches has been reported, which suggests that the starches have some different mechanisms of interacting forces related to its swelling behaviour (Chen et al. 2003).