Study on sweet natural non Muscat wine aroma 1<sup>st</sup> part: qualitative analysis of sweet natural wines aroma found during ageing

Abstract

<p style="text-align: justify;">This work is dedicated to the study of volatile compounds responsible for typical aroma of sweet natural wines, from non Muscat varieties, after ageing. The descriptive sensorial analysis and the modern technics of gas chromatography analysis combined with different detection modes (olfactory detection, and both mass and infrared spectrometry) are used for studying the relationships between the consensual descriptors of the aroma and the volatile substances identified in these wines. The relationships between the data (coming from the descriptive tasting and the volatile compounds and sweet-smelling) are studied thanks to correspondences factorial analysis and principal components analysis. Many substances take part in the characteristic odour of the natural sweet wines after ageing.</p><p style="text-align: justify;">Several volatile odorous compounds identified by the combination of gas chromatography with olfactory detection and mass spectrometry are signaled for the first time in sweet natural wines in this work. However, many of these substances were known in the aroma of several sweet products. Furaneol is always associated with « honey» aroma. Cyclotene (2-hydroxy-3-methyl-2-cyclopenten-I-one), maltol (3-hydroxy-2-methyl-4(<em>H</em>)-pyran-4-one), dihydromaltol (2,3-dihydro-5-hydroxy-6-methyl-4(<em>H</em>)-pyran-4-one), hydroxymaltol (3,5-dihydroxy-2-methyl- 4(<em>H</em>)-pyran-4-one) and DDMP (2,3-dihydro-3,5-dihydroxy-6-methyl-4(<em>H</em>)-pyran-4-one), already known for taking part in « toasty» aroma of heated wood, have been identified in old sweet natural wines extracts, which had never been conserved in a wood barrel.</p><p style="text-align: justify;">Homofuraneol (5(or 2)-ethyl-2(or 5)-methyl-4-hydroxy-3(2<em>H</em>)-furanone), characterised by« caramel» aroma, is found only in young red sweet natural wines. Sotolon (3-hydroxy-4,5-dimethyl-2(5<em>H</em>)-furanone) seems to be characteristic of white swect natural wines. The 5-ethoxymethylfurfural, characterised by a« white bread» aroma with « sharp » and « fruity » shades, have already been found in old red wines. The γ-octalactone and γ-nonalactone, characterised by a strong fruity odour of « coconut », « peach » and « almond », are al ways associated with the « dried-fruits » characteristic aroma of white and rather old sweet natural wines, Pantolactone (3,3-dimethyl-2- hydroxy-γ-butyrolactone) is a quantitatively major compounds in old sweet natural wines, associated in principal component analysis with « plum » aroma in the oldest sweet natural wines. The results enable to know better the volatile compounds which are able to produce ageing aromas charactcristic of sweet natural wines. These products are al ways rich in sugar and grown up in a more or less oxidising environ ment. Logically, many of the compounds identitied in this work (pyranones, furanones and derived esters) seem to be linked with chemicallike Maillard reactions between sugars and amino-acids. Others compounds (sotolon and γ-Iactones) need oxidising phenomena to increase during the ageing of the wines.</p>