Imaging rice grains using atomic force microscopy

Rice (Ogrya sativa) grains from different varieties were examined using atomic force microscopy. Images obtained from cross sections of grains showed angular starch structures 3-8 mum in size that were arranged in layers approximately 400 nm apart. The layers are suggested to represent growth rings of starch granule formation. Cross striations were observed within each layer, and these are suggested to correspond to the blocklets of amorphous and crystalline regions within the starch granule. The blocklets had an average size of 100 nm, and are proposed to comprise approximately 280 amylopectin side chain clusters. Rice grains sectioned with water as a lubricating agent appeared to have lost some of the ordered layered structures, whereas there was a total loss of the ordered structure in cooked grains as a result of gelatinisation. (C) 2003 Elsevier Science Ltd. All rights reserved.