4-5-epoxy-2-decenal and 2-4-decadienal

Coffee, as a source of acrylamide, needs to be investigated in depth to understand the contribution of different precursors. This study aimed to investigate the contributions of sucrose decomposition and lipid oxidation on acrylamide formation in coffee during roasting. Coffee beans and model systems were used to monitor the accumulation of neo-formed carbonyls during heating through sucrose decomposition and lipid oxidation. High resolution mass spectrometry analyses confirmed the formation of 5-hydroxymethylfurfural (HMF) and 3,4-dideoxyosone, which were identified as the major sugar decomposition products in both roasted coffee and model systems. Among others, 2-octenal, 2,4-decadienal, 2,4-heptadienal, 4-hydroxynonenal, and 4,5-epoxy-2-decenal were identified in relatively high quantities in roasted coffee. Formation and elimination of HMF in coffee during roasting had a kinetic pattern similar to those of acrylamide. Its concentration rapidly increased within 10 min followed by an exponential decrease afterward. The amount of lipid oxidation products tended to increase linearly during roasting. It was concluded from the results that roasting formed a pool of neo-formed carbonyls from sucrose decomposition and lipid oxidation, and they play certain role on acrylamide formation in coffee.

Topics: Acrylamide; Aldehydes; Chromatography, Liquid; Coffee; Epoxy Compounds; Food Handling; Furaldehyde; Hot Temperature; Oxidation-Reduction; Sucrose; Tandem Mass Spectrometry

Lipid peroxidation (LPO) processes observed in diseases connected with inflammation involve mainly linoleic acid. Its primary LPO products, 9-hydroperoxy-10,12-octadecadienoic acid (9-HPODE) and 13-hydroperoxy-9,11-octadecadienoic acid (13-HPODE), decompose in multistep degradation reactions. These reactions were investigated in model studies: decomposition of either 9-HPODE or 13-HPODE by Fe(2+) catalyzed air oxidation generates (with the exception of corresponding hydroxy and oxo derivatives) identical products in often nearly equal amounts, pointing to a common intermediate. Pairs of carbonyl compounds were recognized by reacting the oxidation mixtures with pentafluorobenzylhydroxylamine. Even if a pure lipid hydroperoxide is subjected to decomposition a great variety of products is generated, since primary products suffer further transformations. Therefore pure primarily decomposition products of HPODEs were exposed to stirring in air with or without addition of iron ions. Thus we observed that primary products containing the structural element R-CH=CH-CH=CH-CH=O add water and then they are cleaved by retroaldol reactions. 2,4-Decadienal is degraded in the absence of iron ions to 2-butenal, hexanal and 5-oxodecanal. Small amounts of buten-1,4-dial were also detected. Addition of m-chloroperbenzoic acid transforms 2,4-decadienal to 4-hydroxy-2-nonenal. 4,5-Epoxy-2-decenal, synthetically available by treatment of 2,4-decadienal with dimethyldioxirane, is hydrolyzed to 4,5-dihydroxy-2-decenal.

Topics: Air; Aldehydes; Arteriosclerosis; Cations, Divalent; Chromatography, High Pressure Liquid; Epoxy Compounds; Gas Chromatography-Mass Spectrometry; Humans; Hydroxylamines; Iron; Linoleic Acid; Linoleic Acids; Lipid Peroxidation; Lipid Peroxides; Lipoxygenase; Magnetic Resonance Spectroscopy; Models, Chemical; Molecular Structure; Oxidation-Reduction

Six odor-active compounds generated by autoxidation of arachidonic acid (AA) were quantified by isotope dilution assay (IDA), i.e., hexanal (1), 1-octen-3-one (2), (E,Z)-2,4-decadienal (3), (E,E)-2,4-decadienal (4), trans-4,5-epoxy-(E)-2-decenal (5), and (E,Z,Z)-2,4,7-tridecatrienal (6). Compound 1 was the most abundant odorant with about 700 mg/100 g autoxidized AA, which corresponds to 2.2 mol% yield. Based on the odor activity values (ratio of concentration to odor threshold), odorants 3 (fatty) and 5 (metallic) showed the highest sensory contribution followed by 1 (green), 2 (mushroom-like), 6 (egg white-like), and 4 (fatty). For the first time, reliable quantitative results are reported for odorants 1-6 in autoxidized AA, in particular odorant 6, which is a characteristic compound found in autoxidized AA. Synthesis of deuterated 6, required for IDA, is described in detail. The formation of odorants 1-6 by autoxidation of AA is discussed with respect to the quantitative data.

Topics: Aldehydes; Arachidonic Acid; Carbon Isotopes; Chromatography, Gas; Deuterium; Epoxy Compounds; Indicator Dilution Techniques; Isotope Labeling; Isotopes; Ketones; Magnetic Resonance Spectroscopy; Mass Spectrometry; Odorants; Oxidation-Reduction; Stereoisomerism