title: The molecular structural features controlling stickiness in cooked rice, a major palatability determinant.
abstract: The stickiness of cooked rice is important for eating quality and consumer acceptance. The first molecular understanding of stickiness is obtained from leaching and molecular structural characteristics during cooking. Starch is a highly branched glucose polymer. We find (i) the molecular size of leached amylopectin is 30 times smaller than that of native amylopectin while (ii) that of leached amylose is 5 times smaller than that of native amylose, (iii) the chain-length distribution (CLD: the number of monomer units in a chain on the branched polymer) of leached amylopectin is similar to native amylopectin while (iv) the CLD of leached amylose is much narrower than that of the native amylose, and (v) mainly amylopectin, not amylose, leaches out of the granule and rice kernel during cooking. Stickiness is found to increase with decreasing amylose content in the whole grain, and, in the leachate, with increasing total amount of amylopectin, the proportion of short amylopectin chains, and amylopectin molecular size. Molecular adhesion mechanisms are put forward to explain this result. This molecular structural mechanism provides a new tool for rice breeders to select cultivars with desirable palatability by quantifying the components and molecular structure of leached starch.
authors.affiliation: Joint International Research Laboratory of Agriculture and Agri-Product Safety, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu Province, 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: Melissa A
authors.initials: MA
authors.lastname: Fitzgerald
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: Joint International Research Laboratory of Agriculture and Agri-Product Safety, College of Agriculture, Yangzhou University, Yangzhou 225009, Jiangsu Province, China.|The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Gilbert
mesh_terms: D000687:Amylopectin / Q000737:chemistry; D000688:Amylose / Q000737:chemistry; D015394:Molecular Structure; D008970:Molecular Weight; D012275:Oryza / Q000737:chemistry* / Q000235:genetics; D019655:Quantitative Trait, Heritable; D013213:Starch / Q000737:chemistry
chemical_list: D013213:Starch; D000688:Amylose; D000687:Amylopectin