Flour functional properties of purple maize (Zea mays L.) from Argentina. Influence of environmental growing conditions

The objective was to characterize thermal and viscosity properties of flour of purple maize from Argentina, and to evaluate the environmental effects on composition and flour properties. Half-sib families were selected from original germplasm and reproduced during 2014 and 2015. Chemical composition, thermal and pasting properties of whole grain flour were determined. Non-purple genotypes were used as controls. Composition of purple maize did not show significant differences with controls, but amylose content was significantly lower. High variability in pasting and thermal properties of flour was observed between genotypes. Anthocyanin content positively correlated with breakdown (r = 0.37, P < 0.05), indicating that anthocyanins increased starch granules fragility during cooking. The higher gelatinization enthalpy of purple genotypes was coincident with the lower amylose content in relation to non-purple. The amylopectin retrogradation enthalpy negatively correlated with polyphenols (r = -0.35, P < 0.05) and anthocyanins (r = -0.40, P < 0.05), probably due to interactions formed after starch gelatinization. Flour functionality parameters showed higher effect of genotype and lower effects of environment and genotype × environment interaction. The variability found among genotypes indicates different flour behavior that would facilitate the identification of progenies with particular properties for production of functional maize based-foods.

Effects of short-term heat stress at the grain formation stage on physicochemical properties of waxy maize starch

BACKGROUND

Waxy maize (Zea mays L. sinensis Kulesh) suffers short-term exposure to high temperature during grain filling in southern China. The effects of such exposure are poorly understood.

RESULTS

Starch granule size was increased by 5 days' short-term heat stress (35.0 °C) and the increase was higher when the stress was introduced early. Heat stress increased the iodine binding capacity of starches and no difference was observed among the three stages. Starch relative crystallinity was increased and swelling power was decreased only when heat stress was introduced early. Heat stress also increased the pasting viscosity, and this effect became more pronounced with later applications of stress. Heat stress reduced starch gelatinization enthalpy, and the reduction gradually increased with later exposures. Heat stress increased the gelatinization temperature and retrogradation enthalpy and percentage of the samples, with the increases being largest with earlier introduction of high temperature.

CONCLUSION

Heat stress increased the pasting viscosities and retrogradation percentage of starch by causing change in granule size, amylopectin chain length distribution and crystallinity, and the effects observed were more severe with earlier introduction of heat stress after pollination. © 2017 Society of Chemical Industry.