Oily substances (also furfurylaldehyde, formerly furfurol) with aromatic odour and bitter almond taste. These are the aldehyde or a derivative of furan. They are produced, among other things, by the toasting of wooden barrels through the conversion of wood sugars and get into the wine during barrique ageing. They are also contained in wood vinegar and fusel oils. See also under aroma substances.
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