Characterization of maize amylose-extender (ae) mutant starches. Part I: Relationship between resistant starch contents and molecular structures

Endosperm starches were isolated from kernels of seven maize amylose-extender ( ae ) lines: three new ae -lines, derived from a Guatemalan breeding cross with pedigrees of GUAT209:S13 × (OH43 ae × H99 ae ) B-B-4-1-2-1-1, GUAT209:S13 × (OH43 ae × H99 ae ) B-B-4-4-2-1-1, and GUAT209:S13 × (OH43 ae × H99 ae ) B-B-4-4-2-1-2, designated as GSOH1, GSOH2, and GSOH3, respectively, were developed by the USDA-ARS Germplasm Enhancement of Maize (GEM) Project, and four existing inbred lines, H99 ae, OH43 ae , B89 ae , and B84 ae . The resistant starch (RS) contents, measured using AOAC method 991.43 for total dietary fiber, showed that the three new-line starches had larger RS contents (39.4–43.2%) than the four inbred lines (11.5–19.1%). This study was conducted to understand relationship between the RS content and molecular structure of the maize ae-mutant starch. Analytical results showed that the three new-line starches had larger apparent (83.1–85.6%) and absolute amylose-contents (57.4–62.6%) than the starches of the inbred ae -lines (61.7–67.7% and 35.5–44.7%, respectively). The RS content of the ae -mutant starch was positively correlated with both the apparent and absolute amylose-contents of the starch with correlation coefficients of 0.99 and 0.96, respectively. Gel permeation chromatograms revealed that all seven ae starches contained large proportions of intermediate components (IC), 22.4%–52.0%. All seven ae starches displayed similar onset gelatinization temperatures (64.5–65.8 °C), but the three new-line starches displayed higher conclusion temperatures (122.0–130.0 °C) than the four inbred-line starches (100.5–105.3 °C). These results indicated that the crystalline structure of the three new ae- line starches was retained after boiling at ∼100 °C. The crystalline structure was resistant to enzyme hydrolysis and resulted in greater RS contents.