Effects of common cooking heat treatments on selenium content and speciation in garlic

摘要

The effect of traditional thermal treatments, normally applied during cooking practices, on the stability of Se amino acids and Se-proteins present in Se-enriched garlic was studied. Five heat treatments including, convection oven (180 degrees C, 10 min), boiling (100 degrees C, 10 min), microwave oven (800 W, 3 min), steaming (10 min) and stir-frying (180 degrees C, 3 min) were assayed. Modifications on the molecular weight fractions profiles of protein extracts were evaluated by size exclusion chromatography with UV-visible and inductively coupled plasma mass spectrometry (ICP-MS) detection using a 0.05 M Tris(hidroxymethyl)aminomethane solution at pH 7.3 as the mobile phase. Possible modifications of Se-amino acids were evaluated by anion exchange chromatography (AEC), with a 30 mM Na2HPO4 solution (pH 6) as the mobile phase, coupled to ICP-MS after enzymatic hydrolysis. SEC chromatograms showed the incorporation of Se to high (7 kDa) and low molecular weight fractions (2-4 kDa) while AEC chromatograms showed mostly the presence of Se-methylselenocysteine. However, it could be observed that heat treatments significantly affect this important Se-amino acid.