Identification of the main retrogradation-related properties of rice starch.

The retrogradation of rice in shelf life is the biggest barrier to the industrial production of traditional foods using rice as material. Many rice breeders have tried their best to screen low-retrogradation rice cultivars without a specific indicator. To identify the main retrogradation-related properties of rice, the starch, amylose, and amylopectin from 16 rice cultivars were extracted from rice powder and their physicochemical properties, such as visible absorbance, infrared, average molecule weight (amylopectin), chain-length distribution (amylopectin), X-ray diffraction, and differential scanning calorimetry, were determined. The correlation between starch retrogradation rates and those physicochemical properties was investigated. The results show that a significant positive correlation (R(2) = 0.85; r = 0.926; p < 0.01) exists only between proportions of the chains [degree of polymerization (DP) > 10] in amylopectin and the retrogradation rates of different rice starches. The findings in the paper offer a shortcut for rice breeders to screen cultivars with a low retrogradation rate. Because the genes related to the branching enzyme control the DP of amylopectin, they can be exploited as molecular markers to screen low-retrogradation rice cultivars.