Identification of trace volatile compounds in freshly distilled Calvados and Cognac using preparative separations coupled with gas chromatography-mass spectrometry.

Gas chromatography coupled with mass spectrometry (GC-MS) using both electron impact and chemical ionization detection modes led to the determination of the volatile composition of two samples of freshly distilled Cognac and two samples of freshly distilled Calvados. A total of 169 volatile compounds were directly identified in dichloromethane extracts obtained by liquid-liquid extraction. Trace compounds present in both spirits were characterized with the help of preparative separations. In a first step, groups of compounds were separated by preparative GC, and the fractions were analyzed on a polar stationary phase by GC-MS. In a second step, silica gel fractionation was used to separate them by polarity. In this study, 331 compounds, of which 162 can be considered as trace compounds, were characterized in both freshly distilled Cognac and Calvados. Of these, 39 are common to both spirits; 30 are specific to Cognac with numerous hexenyl esters and norisoprenoidic derivatives, whereas 93 are specific to Calvados with compounds such as unsaturated alcohols, phenolic derivatives, and unsaturated aldehydes.

Chemical and sensorial aroma characterization of freshly distilled Calvados. 2. Identification of volatile compounds and key odorants.

Eight samples of freshly distilled Calvados were extracted using pentane. Gas chromatography with either a mass spectrometer or flame ionization detector was used to determine the volatile compounds composition of the extracts. More than 120 molecules were identified in Calvados and then correlated with results obtained by olfactometric analysis in our earlier work [Guichard, H.; Lemesle, S.; Ledauphin, J.; Barillier, D.; Picoche, B. Chemical and Sensorial Aroma Characterization of Freshly Distilled Calvados. 1. Evaluation of Quality and Defects on the Basis of Key Odorants by Olfactometry and Sensory Analysis. J. Agric. Food Chem. 2002, 50, 424-432 (preceding paper in this issue)]. Of these, 16 of the 19 molecules that constitute the "aroma skeleton" were identified, including 5 esters, 2 ketones, 5 phenolic derivatives, 2 alcohols, and 2 carboxylic acids. Numerous compounds were also associated with odors found in part 1. These molecules can be considered as being responsible for the good quality of Calvados or, in contrast, for defects. Relative levels of some major olfactive compounds were also estimated and tentatively compared with olfactometric indices found in part 1. A good correlation was found in many cases. Two important markers of defects in Calvados were also identified. 3-Methylbut-2-en-1-ol leads to an "herbaceous" defect, and 1,1,3-triethoxypropane seems to give an "acrolein" defect in the product. "Floral" notes of the aroma of freshly distilled Calvados seem to be due to the presence of phenolic derivatives such as 2-phenylethanol and 2-phenylethyl acetate. Low-molecular-weight esters such as ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, and 3-methylbutyl acetate give, in general, the "fruity" notes. However, the overall aroma of Calvados seems likely to be a subtle balance of various functionalized compounds.