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Determination of elevated levels of nitrate in vegetable powders by high-precision isotope dilution GC–MS

Pagliano, Enea, Mester, Zoltán
Food chemistry 2019
antioxidant activity, beets, drying, gas chromatography-mass spectrometry, headspace analysis, isotope dilution technique, kale, nitrates, powders, spinach
A high-precision isotope dilution GC–MS method was employed for the determination of nitrate in processed vegetables. The samples were extracted in water, derivatized with triethyloxonium tetrafluoroborate and analyzed by headspace GC–MS (15 samples/hour). The method was applied to estimate the effect of drying on the content of nitrate in vegetables. The absolute amount of nitrate in a spinach sample before and after drying did not change even when the material was baked at 105 °C. Elevated levels of nitrate were found in commercial vegetable powders where the nitrate mass fraction exceed the percent level: 1.2-2.3% NO3- was found in spinach powders, 1.3-1.6% in kale powders, and 1.4% in a beetroot powder. The likely reduction of the antioxidant properties seen in vegetable powders along with their high nitrate content suggest the need to study the risk of endogenous N-nitrosation associated with these products.