ARS | Publication request: Characterization of enzyme-resistant starch in maize amylose-extender mutant starches

Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 28, 2008
Publication Date: June 2, 2008
Citation: Jiang, H., Li, L., Campbell, M., Blanco, M.H., Jay-Lin, J. 2008. Characterization of enzyme-resistant starch in maize amylose-extender mutant starches [abstract]. In: 6th Corn Utilization and Technology Conference Proceedings, June 2-4, 2008, Kansas City, Missouri. p. 33.

Technical Abstract: In the human digestive system, a type of starch known as resistant starch (RS) can not be digested. RS is not absorbed in the small intestine, and is passed to the large intestine where it is fermented by bacteria to produce short-chain fatty acids, which have anti-cancer and anti-inflammatory properties. RS, when consumed, reduces the glycemic index and insulin response. New high-amylose maize lines (ae mutant) GSOH1, GSOH2, and GSOH3, derived from GUAT209:S13 x (H99ae x OH43ae), were developed by Truman State University and the USDA-ARS Germplasm Enhancement of Maize (GEM) Project. The resistant starch content levels of the new ae-line starches (39.4-43.2%), determined using the AOAC 991.43 Method for total dietary fiber, were substantially higher than those of inbred ae-lines H99ae, OH43ae, B89ae, and B84ae (11.5-19.1%). Because of their RS starch levels and properties, these new ae-lines offer great potential for improving human health and nutrition. The objective of this study was to understand the relationship between the starch structures and enzyme-resistance. The new ae-line starches had higher amylose and intermediate component content (86.1-89.3%) than the other inbred ae-line starches (66.5-74.6%). All of the enzyme-resistant starch residues exhibited high onset (To, 107.3-114.4 C), peak (Tp, 118.3-122.4 C), and conclusion (Tc, 125.9-134.0 C) gelatinization temperatures. The X-ray diffraction patterns of the enzyme-resistant starch residues showed B- and V-type crystalline structures. Scanning electron micrographs showed that resistant starch residues (amylose and intermediate components) were concentrated at the periphery of the spherical starch granules and were present in rod/filamentous starch granules. The results suggested that enzyme-resistant starch residues had crystalline structures comprising of long-chain double helices and amylose-lipid complex, which were resistant to enzymatic hydrolysis when heated at 100 C. The amylose and intermediate components in the new ae-line starches were promptly to form long-chain double helices in lamellar crystalline-structures, which resulted in weak birefringence without Maltese-cross when viewed under a polarized light microscope.