Title: COMPRESSION DEFORMATION AND STRUCTURAL RELATIONSHIPS OF COOKED RICE Authors
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2006
Publication Date: April 4, 2006
Citation: Ogawa, Y., Wood, D.F., Orts, W.J., Glenn, G.M. 2006. Compression deformation and structural relationships of cooked rice. Cereal Chemistry. 83 (6): 635-640. (2006) Interpretive Summary: Cooked rice quality is based on factors including texture which is related to structural changes of the interior of cooked rice grain. The texture-structure relationship was explored in this work by correlating compression measurements, meant to mimic a part of the act of chewing, to microstructural disruption of individual compressed grains. Although cooking changes rice grain microstructure, the relationship of structural changes to other quality parameters is unknown. Microstructure of rice grains was observed using adhesive tape to collect sections of intact rice grains. In this paper, we report structural changes that occur in cooked rice grain after compression to a specific percentage, thus relating texture to structure. Specific textural qualities are associated with particular cultivars or types of rice. Various cultivars may differ in the types of microstructural changes occurring upon cooking. Using compression and structural measurements will allow scientists to determine the relationships between rice grain qualities at the microstructural level. The work is expected to expand on the definition and determination of quality attributes in rice.
Technical Abstract: Cooked rice quality is based on factors including texture which is related to structure. The texture-structure relationship can be explored by correlating compression measurements to structural observation of the compressed material. Compression ratios of 20, 30, 40, 50, 60 and 70% were measured against resistance force using a texture analyzer. Structures of cooked rice grains at various compression ratios were compared by microscopy. The outside of an uncompressed, intact, cooked rice kernel is swollen and distorted while the interior has three or more voids. Each void has a large central cavity connected to fine cracks toward the peripheral edges. The voids tend to increase in area up to 40% compression and then decrease in area upon further compression. Compression versus resistance was linear up to 40% compression and then became non-linear. With increasing compression ratio, cell shapes became more rounded although there wasn’t much affect on the integrity of cell walls with increasing compression ratio. The degree to which kernel structure changed during the various compression tests combined with the linear and then non-linear behavior of resistance versus compression, indicates that the voided areas and cell walls affect texture.