AGFD 99 |
| Rice starch, the main component in rice, is mostly responsible for the functional properties of rice ingredients. Generally, rice starch needs modification to develop specific properties such as swelling consistency and gelling stability. Hydrothermal treatments of starch, particularly annealing and moisture-heat treatment, have been studied extensively in recent years. Essentially, annealing is the treatment of starch in excess of water at temperatures below the gelatinization temperature (for rice, 50 –70 oC), whereas moisture-heat treatment is the treatment at relatively lower moisture and higher temperature conditions (for rice, <35% and 100 – 120 oC, respectively). In the processing of starch, these hydrothermal conditions are often applied. It is therefore desirable to study the effect of annealing and moisture-heat treatment on the structural and functional properties of rice starch. In this study, rice starch of long grain and waxy cultivars were treated under annealing or moisture-heat treatment conditions. The modified products were analyzed by Rapid-Visco Analysis (RVA), Differential Scanning Colorimetry (DSC), X-ray diffraction (XRD) and other pertinent analyses. Generally, these treatments altered the pasting and gelling properties of rice starch resulting in lower viscosity peak heights, lower set backs, and greater gelling stability. Specifically, the modified starch showed increased gelatinization temperatures, reduced peak widths or gelatinizaion temperature ranges and the effects are more pronounced for moisture-heat treatment than annealing. Also, the typical A-type XRD pattern for rice starch remained unchanged after annealing, and it changed to a weak V-type after the more severe MHT treatment. The complication in the alteration in the crystallites of the starch granules will be discussed.
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General Posters
1:00 PM-3:00 PM, Monday, 11 September 2006 Moscone Center -- Hall D, Poster
Sci-Mix
Division of Agricultural & Food Chemistry |