engleski

On higher alcohols in wine

Higher alcohols (HA) consist of fusel alcohols, volatile phenols, monoterpene alcohols and in minor quantities other less volatile alcohols. When present in excess concentrations, HA may be regarded as undesirable in wine, but contribute a desirable complexity to the wine aroma in moderate concentrations, below 300 mg/L. Quantitatively, the most important aliphatic higher alcohols are n-propanol (1-propanol), isobutyl alcohol (2-methyl-1-propanol), optically active amyl alcohol (2-methyl-1-butanol) and isoamyl alcohol (3-methyl-1-butanol). Isoamyl alcohol is the main aliphatic higher alcohol, which, depending on the nature of product, makes 40 - 70 % of HA present in different beverages. Among aromatic alcohols in wine, the most important is phenetyl alcohol (2-phenetyl ethanol), and the second is tyrosol. A part of HA may originate from grapes or from spoilage microorganisms but they are mostly found as secondary products of alcoholic fermentation performed by natural or commercial (selected) wine yeast, where they are derived from sugar, amino acids and sulphur metabolism of yeast. HA production should be taken in account as a selection criterion of commercial yeast strains. It has been shown that by using immobilized yeasts on different supports, HA are produced in lower concentrations than in the same wines with free cells, which was favourable to aromatic profiles of wines. No genetically engineered yeast is currently used in commercial wine production and the commercialisation of genetically modified yeast is not probable in the near future. Determination of HA/FA can be performed with colorimetric, GC or GC/MS methods. Colorimetric method is used to determine HA as a group of compounds. Individual determination of some HA is possible by using packed or capillary columns combined with specific detectors as flame ionisation detector (FID) and mass spectrometry (MS) detector. Sample preparation is sometimes necessary using solid phase micro extraction (SPME).

wine; higher alcohols; fusel alcohols; determination of higher alcohols

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