Browsing by Subject "Phosphate-availability"

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The influence of phosphate-availability and phytic acid on the profiles of fatty acids, (poly)phenols, carotenoids, and tocochromanols in maize (Zea mays L.) grains – from field experiments to human in vitro digestion studies
(2022) Lux, Peter Erwin; Frank, Jan
Phosphorus (P) is an essential element for living organisms and involved in phosphorylation reactions, including the biosynthesis of several organic micronutrients. Since P is taken up by plants from soil as phosphates, phosphate fertilizers are applied on fields to support the P-supply for crops. Today, shrinking global P-resources demand a reduction in the application of P-containing fertilizers, but knowledge about possible effects of a reduced phosphate-availability in soils on the quality of maize grains is lacking. Thus, it was hypothesized that a reduced phosphate-availability in soil influences the concentrations of dietary organic compounds (phenolics, fatty acids, carotenoids, and tocochromanols) in grains of maize during cultivation. Moreover, concentration differences in the P-storage form phytic acid in maize grains may impact the oxidative stability of these organic compounds during processing and digestion. Fertilizer experiments with maize hybrids were conducted at study sites with low to high phosphate concentrations in soil (1.6 to 20.6 mg CAL-P/100 g soil) in Germany. GC-MS or HPLC-(MS) analyses of the ground maize grains revealed the identity of fatty acids, insoluble (mostly diferulic and triferulic acids) and soluble (poly)phenols, carotenoids, and tocochromanols. The concentrations of these (poly)phenols, carotenoids, and tocochromanols as well as the fatty acid composition in the grains of the maize plants grown with or without phosphate fertilizer were not significantly (p < 0.05) different. Interaction effects between phosphate application and the locations on the fatty acid composition as well as on carotenoids and tocochromanols were considered as insignificant, concluding that a reduction in phosphate fertilization could be implemented on most fields in Germany when only considering these dietary compounds. Lastly, the influence of phytic acid on oxidation processes in maize during processing of porridge and in vitro digestion was examined. Porridges were prepared from maize flour containing either high phytic acid concentration or low phytic acid concentration supplemented with or without phytate. The porridges were digested using a human in vitro digestion model, resulting in a decrease in tocochromanols, carotenoids and unsaturated fatty acids. Oxidation products (alpha-tocopherylquinone, malondialdehyde) were formed in all samples, implying that phytic acid addition did not show the expected protective effect. The addition of phytate evoked a significant reduction in the micellarization efficiency of most carotenoids. Thus, the knowledge about phytic acid as antinutrient was extended.