Toxicologically Relevant Aldehydes Produced during the Frying Process Are Trapped by Food Phenolics.
The lipid-derived carbonyl trapping ability of phenolic compounds under common food processing conditions was studied by determining the presence of carbonyl-phenol adducts in both onions fried in the laboratory and commercially crispy fried onions. Four carbonyl-phenol adducts produced between quercetin and acrolein, crotonaldehyde, or (E)-2-pentenal were prepared and characterized by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy and high performance liquid chromatography coupled to high resolution mass spectrometry (HPLC-HRMS). The synthesized compounds were 2-(3,4-dihydroxyphenyl)-3,5,8-trihydroxy-9,10-dihydro-4H,8H-pyrano[2,3-f]chromen-4-one (4), 2-(3,4-dihydroxyphenyl)-3,5,8-trihydroxy-10-methyl-9,10-dihydro-4H,8H-pyrano[2,3-f]chromen-4-one (5), 2-(3,4-dihydroxyphenyl)-3,5-dihydroxy-8-methyl-4H,8H-pyrano[2,3-f]chromen-4-one (9), and 2-(3,4-dihydroxyphenyl)-8-ethyl-3,5-dihydroxy-4H,8H-pyrano[2,3-f]chromen-4-one (10). When onions were fried in fresh rapeseed oil spiked with acrolein, crotonaldehyde, and (E)-2-pentenal (2.7 μmol/g of oil), adduct 10 was the major compound produced, and trace amounts of adducts 4 and 5, but not of adduct 9, were also detected. In contrast, compound 4 was the major adduct present in commercially crispy fried onions. Compound 10 was also present to a lower extent, and trace amounts of compound 5, but not of compound 9, were also detected. These data suggested that lipid-derived carbonyl-phenol adducts are formed in food products under standard cooking conditions. They also pointed to a possible protective role of food polyphenols, which might contribute to the removal of toxicologically relevant aldehydes produced during deep-frying, assuming that the formed products are stable during food consumption in the human organism.
Instituto de la Grasa, Consejo Superior de Investigaciones Científicas, Carretera de Utrera km 1, Campus Universitario - Edificio 46, 41013-Seville, Spain.
Rosario
R
Zamora
Instituto de la Grasa, Consejo Superior de Investigaciones Científicas, Carretera de Utrera km 1, Campus Universitario - Edificio 46, 41013-Seville, Spain.
Isabel
I
Aguilar
Lehrstuhl für Lebensmittelchemie, Techniche Universität München , Lise-Meitner-Straβe 34, D-85354 Freising, Germany.
Michael
M
Granvogl
Instituto de la Grasa, Consejo Superior de Investigaciones Científicas, Carretera de Utrera km 1, Campus Universitario - Edificio 46, 41013-Seville, Spain.
Francisco J
FJ
Hidalgo
D000447:Aldehydes / Q000737:chemistry* / Q000633:toxicity*; D003296:Cooking; D006358:Hot Temperature; D019697:Onions / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry* / Q000633:toxicity; D010938:Plant Oils / Q000737:chemistry* / Q000633:toxicity
D000447:Aldehydes; D010636:Phenols; D010938:Plant Oils
aldehydes; carbonyl-phenol reactions; deep-frying; fried onions; lipid oxidation; quercetin; reactive carbonyls