Rice starch granule amylolysis – Differentiating effects of particle size, morphology, thermal properties and crystalline polymorph. (22nd January 2015)

• Record Type: Journal Article
• Authors: Dhital, Sushil; Butardo, Vito M.; Jobling, Stephen A.; Gidley, Michael J.
• Is Part Of: Carbohydrate polymers. Volume 115(2015)
• Page Start: 305
• Page End: 316
• Publication Date: 2015-01-22
• Subjects: Amylopectin -- Amylose -- Amylose Extender -- Digestibility -- High amylose -- Starch structure; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2014.08.091
• Languages: English
• ISSNs: 0144-8617

Abstract

Highlights: Starch granule digestion studied for rice lines differing in crystalline polymorph. Both A- and B-type crystalline granules have surface pores. Patterns of hydrolysis similar but B-type granules more enzyme resistant. Suggests that amylopectin branch lengths are the major underlying factor. Abstract: The underlying mechanism of amylolysis of rice starch granules was investigated using isolated starch granules from wild-type, as well as SBEIIb mutant and down-regulated lines. Fused granule agglomerates isolated from mutant and transgenic lines were hydrolysed at similar rates by amylases, and had similar crystalline patterns and thermal properties as individual granules. Surface pores, a feature previously only reported for A-polymorphic starch granules, were also observed in B- and C-polymorphic rice starch granules. Although the microscopic patterns of hydrolysis among granules with different crystalline polymorphs were qualitatively similar, the extent and the rate of amylolysis were different, suggesting that B-type crystalline polymorphs are intrinsically more resistant to enzymatic hydrolysis than A-type in rice starch granules. It is proposed that the slightly longer branch lengths of amylopectin which leads to the formation of more stable B-type double helical structures compared to their A-type counterparts is the major parameter, with other factors such as granule size, surface pores and interior channels having secondary roles, in determining the rate of enzymatic hydrolysis of rice starch granules.