Changes in odour of bartlett pear brandy influenced by sunlight irradiation

Sensory evaluation of Bartlett pear brandy revealed differences in taste and smell between the brandy in colourless and green bottles. To determine the differences in chemical composition, headspace sampling with solid-phase microextraction combined with gas chromatography-mass spectrometry was applied. The major aroma components in pear brandy stored in green bottles were ethyl trans-2-cis-4-decadienoate (68 ppm), ethyl trans-2-trans-4-decadienoate (21 ppm) and methyl trans-2-cis-4-decadienoate (27 ppm). In pear brandy kept in colourless bottles, the concentration of trans-2-cis-4-isomeres was lower and the concentrations of other possible isomeres were higher. Results show a pronounced difference in the concentration ratios among isomeres of ethyl 2,4-decadienoate and methyl 2,4-decadienoate in both samples. Sunlight irradiation was found to be the reason for these changes. It was confirmed that trans-2-cis-4-isomere partly converts to the other three isomeres during UV irradiation.