FURAN DERIVATIVES : ITS OCCURRENCE IN FOODS, CONTRIBUTION TO MELANOIDIN FORMATION, METABOLISM

Swasti, Yuliana Reni (2012) FURAN DERIVATIVES : ITS OCCURRENCE IN FOODS, CONTRIBUTION TO MELANOIDIN FORMATION, METABOLISM. Phd thesis, UAJY.

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Abstract

Furan could be formed by heating of L–ascorbic acid, amino acids, reducing sugars, and fatty acids. Nevertheless, the mechanism of formation of furan derivatives differs among each other but all are formed by heating of one or two of the precursors. Furan and its derivatives give a positive benefit tothe sensory properties of heated food but also have toxic and in some cases mutagenic effects. Moreover, the polymerization of furfuryl alcohol as furan derivative contributes to the formation of the brown colour in heated foods, besides Maillard and caramelization reactions. During heating of food, furfuryl alcohol is formed through degradation of quinic acid or 1,2–enediols. Furfuryl alcohol is a mutagenic compound. In acid conditions it is able to polymerize and form aliphatic polymers that show a brown colour. In addition, some of those furans still remain in the liver or kidney whichcan be metabolized forming toxic or mutagenic compounds that bind to proteins or DNA. In this research project it was shown that the HPLC using gradient elution with methanol and water can be used for the identification and quantification of HMF, furfuryl alcohol, and furfural in a single run. Instant coffee powder, ready–to–drink filter coffee, and cappuccino contain 5–hydroxymethylfurfural (HMF), furfuryl alcohol, and furfural. Dried plums and raisins also contain HMF and furfural. Crisp bread contains furfuryl alcohol and HMF. Besides that, goat cheese contains furfuryl alcohol and cola beverage contains HMF. The analysed samples were provided by the Norwegian Institute of Public Health investigating the exposure to these substances in Norway. Furthermore, here we show that furfuryl alcohol polymerizes in a model system by incubationin 1 M HCl at room temperature. Some of the reaction products are oligomers with dimers, trimers, tetramers, and pentamers having a methylene linkagebeing identified. The degree of polymerization and the amount of those furfuryl alcohol oligomers increases with increasing reaction time. The results of this model system were used to characterize the polymerization of furfuryl alcohol during roasting of coffee. The coffee was roasted at 210 °C for 2, 3, 4, 5, and 6 min using a home coffee roaster. Furfuryl alcohol and its dimer were found in coffee after 2 and 3 min of roasting reaching a maximum amount after 4 min; probably due to further reactions the dimeric furfuryl alcohol concentration starts to decrease after 4 min. We propose that the polymers of furfuryl alcohol contribute to the brown colour of roasted foods. In urine, the 5–hydroxymethyl– 2–furoic acid as metabolite of HMF and 2–furoic acid as metabolite of furfuryl alcohol and furfural can be analysed by HPLC separation and 5-methyl furoic acid as metabolite of 5-methylfurfural and 5-methyl furfuryl alcohol only can be analysed by LC/MS/MS after alkaline treatment to hydrolyse the glycine conjugates.

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