Aroma-Active Compounds in Bartlett Pears and Their Changes during the Manufacturing Process of Bartlett Pear Brandy

Application of aroma extract dilution analysis to Bartlett pears and the fermented mash produced thereof revealed 24 and 34 aroma-active compounds in the flavor dilution (FD) factor range between 8 and 8192. Twenty-eight compounds, which have not been described before in Bartlett pears or in fermented pear mash, were identified. While ethyl (E,Z)-2,4-decadienoate (pear-like, metallic odor impression), hexyl acetate (green, fruity), and acetic acid (vinegar-like) showed the highest concentrations in Bartlett pears, ethanol (ethanolic), acetic acid, 3-methyl-1-butanol (malty), 1-hexanol (grassy, marzipan-like), (S)-2- and 3-methylbutanoic acid (sweaty), and 2-phenylethanol (flowery, honey-like) were present at the highest amounts in the fermented mash. The key aroma compounds were quantitated in each pear brandy production step (pears, fermented mash, distillate, and aged distillate) by stable isotope dilution analysis showing a clear influence of each step on the overall aroma of the spirit and, consequently, revealing clearly changing concentrations (e.g., of ethyl (S)-2-methylbutanoate, (E)-β-damascenone, ethyl (E,Z)-2,4-decadienoate, and ethyl (E,E)-2,4-decadienoate) and different aroma perceptions during the manufacturing process. In addition, the concentrations of the so-called "pear esters" ethyl (E,Z)-2,4-decadienoate and ethyl (E,E)-2,4-decadienoate were determined in 6 different pear varieties (Abate Fetel, Anjou, Bartlett, Forelle, Kaiser Alexander, and Packham's Triumph) clearly demonstrating the aroma potential of the variety Bartlett, which is mostly used for brandy production due to the high amounts of both esters eliciting a typical pear-like odor impression.