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.

Physicochemical properties of vitreous and floury endosperm flours in maize

“…Peak time (PT) and pasting temperature (P temp ) of vitreous and floury endosperm flour ranged from 4.67 to 4.73 min and 71.00 to 72.55°C, and from 4.00 to 4.47 min and 69.35 to 70.25°C, respectively (Table ). Floury endosperm flour showed a lower PT and P temp than vitreous endosperm flour, which was similar to highly compact kernels with a high percentage of hard endosperm requiring more time and higher temperature for gelatinization (Mansilla et al, ; Narváez‐González et al, ). In vitreous endosperm, protein matrix clung to the surface of starch granules (Zhang et al, ).…”

“…The values of PV and BD were also either increased or decreased, depending on protein type and its concentration (Li et al, ; Noisuwan, Bronlund, Wilkinson, & Hemar, ). It was hypothesized that certain proteins formed a matrix and then restrain swelling, and consequently, lower viscosity was observed with higher protein content (Li et al, ; Mansilla, Nazar, & Pérez, ). Furthermore, as the dilution factor, proteins reduced the starch water absorption with the ensuing decrease in viscosity (Baxter, Blanchard, & Zhao, ; Mansilla et al, ).…”

“…It was hypothesized that certain proteins formed a matrix and then restrain swelling, and consequently, lower viscosity was observed with higher protein content (Li et al, ; Mansilla, Nazar, & Pérez, ). Furthermore, as the dilution factor, proteins reduced the starch water absorption with the ensuing decrease in viscosity (Baxter, Blanchard, & Zhao, ; Mansilla et al, ). Therefore, the lower PV and BD of vitreous endosperm flour should relate to the bigger granules (Table ), higher ratio of long chain in the starch (Table ), and higher protein content and lower starch content (Table ).…”

“…The values of PV and BD were also either increased or decreased, depending on protein type and its concentration (Li et al, 2018;Noisuwan, Bronlund, Wilkinson, & Hemar, 2008). It was hypothesized that certain proteins formed a matrix and then restrain swelling, and consequently, lower viscosity was observed with higher protein content (Li et al, 2018;Mansilla, Nazar, & Pérez, 2017).…”

“…Furthermore, as the dilution factor, proteins reduced the starch water absorption with the ensuing decrease in viscosity (Baxter, Blanchard, & Zhao, 2014;Mansilla et al, 2017). Therefore, the lower PV and BD of vitreous endosperm flour should relate to the bigger granules (Table 2), higher ratio of long chain in the starch (Table 3), and higher protein content and lower starch content (Table 1).…”