Physicochemical properties and structure of starches from Chinese rice cultivars

Starches from 10 different non-waxy rice cultivars in China were isolated and investigated for their physicochemical properties including the swelling power, solubility, syneresis, thermal, rheological and textural properties, and structure. The range of amylose content in 10 rice starches was between 18.1 and 31.6%. The branch chain length distribution of amylopectin revealed that the proportions of short (DP6–11), medium (DP12–17), and longer chains (DP18–23) were 4.6–11.1%, 47.0–51.6% and 25.3–31.8%, respectively. The relationships between different properties of rice starches were determined using Pearson correlation analysis. Amylose content was negatively correlated to swelling power (r = −0.632, p ≤ 0.05) and positively correlated to gel hardness (r = 0.776, p ≤ 0.01). The percentage of short chains (DP6–11) was negatively related to the transition temperatures (To, Tp and Tc), ToG′ and TG′max, while the percentage of medium chains (DP12–23) was positively related. Various branch chain length amylopectins played different roles in rheological behavior of starch dispersions. The percentage of short chains (DP6–11) was positively correlated to G′ and G″(r = 0.832 and r = 0.775, respectively, p ≤ 0.01), and negatively correlated to tanδ peak (r = −0.717, p ≤ 0.05). However, the percentage of longer chains (DP18–23) showed a negative relation with G′ and G″ (r = −0.794, p ≤ 0.01; r = −0.741, p ≤ 0.05), and a positive relation with tanδ peak (r = 0.668, p ≤ 0.05).