title: The importance of amylose and amylopectin fine structure for textural properties of cooked rice grains.
abstract: Statistically and causally meaningful relationships are established between starch molecular structure (the molecular distribution of branched starch and the chain length distribution of debranched starch) and texture (hardness and stickiness) of cooked rice grains. The amounts of amylose chains with degree of polymerization (DP) 100-20,000, and of long amylopectin chains, positively correlated with hardness, while amylopectin chains with DP<70 and amylose molecular size both showed negative correlations with hardness (p<0.05). There was also a significant negative correlation between stickiness and the amounts of long amylopectin chains (p<0.01). For rices with similar amylose content, the amount of amylose chains with DP 1000-2000 positively correlated with hardness while size negatively correlated with hardness (p<0.05). This indicates for the first time that, regardless of amylose content, rice varieties with smaller amylose molecular sizes and with higher proportions of long amylose chains have a harder texture after cooking.
authors.affiliation: School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Li
authors.affiliation: The University of Queensland, School of Agriculture and Food Science, Brisbane 4072, QLD, Australia.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Prakash
authors.affiliation: The University of Queensland, School of Chemical Engineering, Brisbane 4072, QLD, Australia.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Nicholson
authors.affiliation: The University of Queensland, School of Agriculture and Food Science, Brisbane 4072, QLD, Australia.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Fitzgerald
authors.affiliation: School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia. Electronic address: b.gilbert@uq.edu.au.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Gilbert
mesh_terms: D000687:Amylopectin / Q000737:chemistry*; D000688:Amylose / Q000737:chemistry*; D003296:Cooking; D015394:Molecular Structure; D012275:Oryza / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry
chemical_list: D010936:Plant Extracts; D000688:Amylose; D000687:Amylopectin
keywords: Amylopectin; Amylose; Hardness; Rice; Sensory properties; Size exclusion chromatography; Stickiness