Determining the effects of microwave heating on the ordered structures of rice starch by NMR

The effects of microwave heating on the double helices, single helix and amorphous structures and the relative crystallinity of rice starch were studied by C-13 CP/MAS NMR method, with rapid heating in an oil bath and conventional slow heating as controls. The results indicated that compared with rapid heating, microwave heating did not significantly change the ordered and disordered structures. All of the heating methods exhibited similar content changes to the double helices, V-type single helix and amorphous structures with rising temperature. The rapid heating effects caused by microwave and oil bath accelerated the destruction of the V-type single helix in the starch granules. The electromagnetic effect of microwave heating did not affect the decrease of the double helices or the amorphous content of the starch. (C) 2012 Elsevier Ltd. All rights reserved.