Fractionation of wild rice (Zizania palustris) polysaccharides and characterization of the starch fraction

Fractionation of polysaccharides in wild rice (Zizania palustris) grain yielded 30.5% starch and 3.54% cell wall. Scanning electron microscopy showed that the starch granules were angular and polygonal but smaller in size, and that the cell wall layer appeared to be thicker and stronger than that of rice. The unit chain distributions in the starch molecule were examined by gel-filtration and high-performance anion-exchange chromatography of the completely enzymatically debranched materials. Gel-filtration showed that the amount of Fr. I (amylose) of wild rice was 23.8% higher than that of rice. The ratio of Fr. III/Fr. II on the gel-filtration chromatogram was 3.5, which was higher than the value of 2.6 obtained for rice starch. Detailed unit chain analysis by high-performance anion-exchange chromatography indicated that the proportion of DP10-14 (with a peak of DP11) was higher than that of rice starch. Thus, the contents of amylose and also short-chain-units were higher than those of rice starch, suggesting a close relationship to the unique texture of wild rice.