Comparison of flour starch properties in half-sib families of opaque-2 maize (Zea mays L.) from Argentina

Abstract

Since the discovery of the o2 mutation in maize, many studies have reported the characterization of the protein quality of opaque-2 genotypes. However, few have reported the properties of their starch. The objective of this study was to characterize flour starch properties of 12 half-sib families of opaque-2 maize from Argentina. Chemical composition and thermal and pasting properties of whole grain flour were determined. Nonopaque genotypes were used as a control. Starch content of opaque-2 genotypes did not show significant differences compared with nonopaque genotypes, yet amylose content was significantly lower. A high variability in pasting and thermal properties was observed in genotypes. Opaque samples showed a significantly higher peak viscosity and a lower pasting temperature compared with nonopaque samples, probably owing to larger and less compact starch granules in the floury endosperm. The higher the gelatinization enthalpy of opaque-2 genotypes was, the lower the amylose content in relation to nonopaque varieties. Two retrogradation endotherms were observed in DSC analysis: one corresponding to amylopectin crystallization and the other to melting of amylose-lipid complex. Both enthalpies were considered total starch retrogradation (ΔHRT). A wide range of variation was obtained in ΔHRT in opaque-2 genotypes, but no significant differences between opaque and nonopaque genotypes were observed. The differences in starch properties found in this study would make it possible to identify opaque-2 families with particular characteristics for the development of starchy food items adapted to specific processing traits.