Properties of the starches of maize and its botanically related plants.

The distribution of components and hydrolysis patterns by glucoamylase were investigated for the starches prepared from maize (Zea mays L.) having either one or two of recessive endosperm genes, namely waxy (wx), dull (du), sugary-1 (sul), sugary-2 (su2), and amylose-extender (ae). Properties of residual ae and sue starches after glucoamylase hydrolysis were also examined. The wx gene decreased the amylose content and increased starch granule susceptibility to glucoamylase. When the du gene was combined with the sul or sue gene, amylose content of the starches increased. The ratio of short chains of amylopectin increased through the introduction of the du or sul genes. The proportions of amylose, intermediate fraction, and long chains of amylopectin increased when the ae gene was introduced. The ae starch granules had lower susceptibility to glucoamylase than that of the normal maize, and very slow stage of hydrolysis appeared after 80-85% degradation. The residual ae starch on the slow stage accumulated the low-molecular-weight materials which were not shown in the original starch. Similar materials were present in the redidual sue starches, but not in those of the normal maize. Properties of these materials were investigated, and the relation to crystal region in the starch granules was discussed. Starch granules were prepared from seeds of Job's tears [hatomugi, Coix lacryma jobi L. mayuen (Roman) Stapf, and juzudama, Coix lacryma jobi L.] and sorghum [Sorghum bicolor(L.) Moench] which were collected in Japan, Korea, and Indonesia. The distribution of components, gelatinization characteristics, and susceptibility to amylases of the starches were investigated. The properties of hatomugi and juzudama starches were similar to those of waxy and normal type of maize starches, respectively. Sorghum starches of nonwaxy type showed wide variation in the amylose content. Starch granules of all sample seeds had higher susceptibility to amylases than that of normal maize.