Abstract
Japanese millet starch was prepared from Japanese millet flour with aqueous alkali by the centrifuge method, and the starch obtained was compared with that prepared by the conventional method. Japanese millet flour was washed 1 or 3 times with 0.2% (w/v, 0.05 M) or 0.3% (w/v, 0.075 M) aqueous sodium hydroxide, and the optimum conditions for obtaining pure starch from Japanese millet in a short time were investigated. The yield of Japanese millet starch was 44-47% by the centrifuge method, whereas that by the conventional method was 40%. The protein content (0.29-0.35%) and ash content (0.08-0.10%) of the starch samples did not differ significantly with either preparation method. Gel chromatography showed that the apparent amylose content of Japanese millet starch (Fr. I), long-chain amylopectin (Fr. II) and short-chain amylopectin (Fr. III) was 23%, 19% and 58.3%, and the Fr. III/Fr.II ratio was 3.1. The average diameter of the Japanese millet starch granules was 7.0-7.4 μm. The results from the Rapid Visco-Analyser showed that Japanese millet starch prepared by the centrifuge method had a higher maximum viscosity and cooled at 50°C viscosity, lower minimum viscosity and greater breakdown value. The gel texture of the starch samples differed according to the preparation method, the sample prepared by one wash with 0.2% (0.05 M) alkali being the softest. There was correlation between the firmness of the gel and breakdown value measured with the Rapid Visco-Analyser. The centrifuge method was used to prepare Japanese millet starch in 2-3 days with high purity and yield, compared with 2-3 weeks by the conventional method. One wash with 0.2% (0.05 M) alkali was sufficient.
