Preparation of granular cold water soluble rice starches having different amylose contents
2010
Roselawatee Toae(Kasetsart University, Bangkok (Thailand). Faculty of Agro-Industry. Department of Biotechnology) E-mail:wateebanana@hotmail.com | Pathama Chatakanonda(Kasetsart University, Bangkok (Thailand). Kasetsart Agricultural and Agro-Industrial Product Improvement Institute) | Rungtiva Wansuksri(National Science and Technology Development Agency, Pathum Thani (Thailand). National Center for Genetic Engineering and Biotechnology. Cassava and Starch Technology Research Unit) | Kuakoon Piyachomkwan(National Science and Technology Development Agency, Pathum Thani (Thailand). National Center for Genetic Engineering and Biotechnology. Cassava and Starch Technology Research Unit) | Klanarong Sriroth(Kasetsart University, Bangkok (Thailand). Faculty of Agro-Industry. Department of Biotechnology)
Granular cold water soluble (GCWS) rice starches were prepared by an alcoholic-alkaline treatment using three rice starches with different amylose contents (37.49, 22.26 and 9.43 percent, as determined by a spectrophotometric method for High amylose-HA, Medium amylose-MA and Low amylose- LA rice starches, respectively). To prepare GCWS starches, rice starches were suspended in an aqueous ethanol (1:20 by weight) and mixed with 3M sodium hydroxide solution at different ratios of 2.0-6.0. The GCWS rice starches with the maximal cold water solubility (greater than 75 percent) could be prepared by using different ethanol concentrations and amounts of alkali. The GCWS of HA and MA rice starches having higher onset gelatinization temperature than the LA rice starch (the onset temperatures as determined by a Differential Scanning Calorimeter were 63.03, 63.43 and 59.49 deg C for HA, MA and LA rice starches, respectively) were prepared by using 40 percent ethanol. In contrast, the preparation of GCWS from LA rice starch had to be performed under the restricted condition of water content, using 95 percent ethanol, otherwise starch was completely dispersed (gelatinized). The amounts of alkali for preparing the GCWS of HA, MA and LA rice starches were 4.0, 3.0 and 4.0, respectively. When determined by a Rapid Visco Analyzer, the paste viscosity of GCWS starches was equivalent or higher than cooked pastes of native starches. The Brookfield analysis of GCWS rice starches exhibited similar paste properties as cooked paste of native starches, i.e. having shear thinning and thixotropic behavior.
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