The molecular structures of leached starch during rice cooking are controlled by thermodynamic effects, rather than kinetic effects. (December 2017)

• Record Type: Journal Article
• Authors: Li, Hongyan; Wen, Yangyang; Wang, Jing; Sun, Baoguo
• Is Part Of: Food hydrocolloids. Volume 73(2017)
• Page Start: 295
• Page End: 299
• Publication Date: 2017-12
• Subjects: Thermodynamic -- Kinetic -- Leached starch -- Molecular size -- Chain-length distribution; Hydrocolloids -- Periodicals; Food additives -- Periodicals; Colloïdes -- Périodiques; Aliments -- Additifs -- Périodiques; Colloids; Food additives; Periodicals; Electronic journals; 664.06
• DOI: 10.1016/j.foodhyd.2017.07.015
• Languages: English
• ISSNs: 0268-005X

Abstract

Abstract: The structure features (both molecular size and chain-length distribution) of leached starch during rice cooking are of prime importance to the stickiness of cooked rice. In the present study, the effects of cooking temperature (thermodynamic effects) and cooking time (kinetic effects) during rice cooking on the structural features of leached starch are explored using different rice varieties in terms of amylose content. We show that (i) the molecular sizes of the leached starch at varying conditions are mainly distributed between 1 and 100 nm, while the chain-length distribution of leached starch at varying conditions are ranged at DP 1–1000, displaying significantly different structural features with the starch in the whole grain; (ii) the effects of cooking temperature on these structural features are cultivar-specific, and much more significant than the effects of cooking time, indicating that the molecular size and chain-length distribution of leached starch during rice cooking are controlled by thermodynamic effects, rather than kinetic effects; (iii) the leached amylose content of non-waxy rice varieties increase with the cooking temperature increasing, revealing that it is small amylopectin easier to leach out of rice kernel, instead of amylose. These molecular structural characterizations provide new understandings of starch leaching and leached starch in terms of improving the cooking and eating quality of cooked rice. Graphical abstract: Highlights: Molecular structures of leached starch are different from that of whole-grain starch. Structural features during starch leaching are controlled by thermodynamic effects. Small amylopectin leach out rice kernel easier during rice cooking.