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Cereal Chem. 83(5):569-575The effects of amylose, protein, and fiber contents on ethanol yields were evaluated using artificially formulated media made from commercial corn starches with different contents of amylose, corn protein, and corn fiber, as well as media made from different cereal sources including corn, sorghum, and wheat with different amylose contents. Second-order response-surface regression models were used to study the effects and interactions of amylose, protein, and fiber contents on ethanol yield and conversion efficiency. The results showed that the amylose content of starches had a significant (P < 0.001) effect on ethanol conversion efficiency. No significant effect of protein content on ethanol production was observed. Fiber did not show a significant effect on ethanol fermentation either. Conversion efficiencies increased as the amylose content decreased, especially when the amylose content was >35%. The reduced quadratic model fits the conversion efficiency data better than the full quadratic model does. Fermentation tests on mashes made from corn, sorghum, and wheat samples with different amylose contents confirmed the adverse effect of amylose content on fermentation efficiency. Hightemperature cooking with agitation significantly increased the conversion efficiencies on mashes made from high-amylose (35-70%) ground corn and starches. A cooking temperature of ≥160°C was needed on highamylose corn and starches to obtain a conversion efficiency equal to that of normal corn and starch.

GEMS-0067 maize starch contains up to 32% elongated starch granules, much higher than amylose-extender (ae) single-mutant maize starch (∼7%) and normal (non-mutant) maize starch (0%). These elongated granules are highly resistant to enzymatic hydrolysis at 95-100 °C, which function as resistant starch. The structure and formation of these elongated starch granules, however, were not known. In this study, light, confocal laser-scanning, scanning electron, and transmission electron microscopy were used to reveal the structure and formation of these elongated starch granules. The transmission electron micrographs showed fusion through amylose interaction between adjacent small granules in the amyloplast at the early stage of granule development. A mechanistic model for the formation of elongated starch granules is proposed. a b s t r a c t GEMS-0067 maize starch contains up to 32% elongated starch granules, much higher than amyloseextender (ae) single-mutant maize starch (7%) and normal (non-mutant) maize starch (0%). These elongated granules are highly resistant to enzymatic hydrolysis at 95-100°C, which function as resistant starch. The structure and formation of these elongated starch granules, however, were not known. In this study, light, confocal laser-scanning, scanning electron, and transmission electron microscopy were used to reveal the structure and formation of these elongated starch granules. The transmission electron micrographs showed fusion through amylose interaction between adjacent small granules in the amyloplast at the early stage of granule development. A mechanistic model for the formation of elongated starch granules is proposed.

GEMS-0067 (PI 643420) maize line is a homozygous mutant of the recessive amylose-extender (ae) allele and an unknown number of high-amylose modifier (HAM) gene(s). GEMS-0067 produces starch with a approximately 25% higher resistant-starch (RS) content than maize ae single-mutant starches. The objective of this study was to understand how the HAM gene(s) affected the RS content and other properties of ae-background starches. Nine maize samples, including G/G, G/F1, G/H, F1/G, F1/F1, F1/H, H/G, H/F1, and H/H with HAM gene-dosages of 100, 83.3, 66.7, 66.7, 50, 33.3, 33.3, 16.7, and 0%, respectively, were produced from self- and intercrosses of GEMS-0067 (G), H99ae (H), and GEMS-0067xH99ae (F1) in a generation-means analysis (GMA) study. RS contents of examined starches were 35.0, 29.5, 28.1, 32.0, 28.2, 29.4, 12.9, 18.4, and 15.7%, respectively, which were significantly correlated with HAM gene-dosage (r = 0.81, p < 0.01). Amylose content, number of elongated starch granules, and conclusion gelatinization temperature increased with the increase in HAM gene-dosage. X-ray diffraction study showed that the relative crystallinity (%) of starch granules decreased with the increase in HAM gene-dosage. The results suggested that the HAM gene-dosage was responsible for changes in starch molecular structure and organization of starch granules and, in turn, the RS formation in the maize ae mutant starch.