Changes in the Key Odorants of Italian Hazelnuts (Coryllus avellana L. Var. Tonda Romana) Induced by Roasting

Application of a comparative aroma extract dilution analysis on aroma distillates isolated from either raw Italian hazelnuts or a roasted hazelnut material produced thereof revealed 37 odor-active compounds in the raw nuts, whereas 46 aroma compounds were detected in the roasted nut material. 2-Methoxy-3-isopropylpyrazine and 2-methoxy-3,5-dimethylpyrazine as well as 5-methyl-4-heptanone predominated with the highest flavor dilution factors in the raw nuts, whereas 2-acetyl-1-pyrroline, 2-propionyl-1-pyrroline, 2-furfurylthiol, and 2-thenylthiol as well as (2)-2-octenal, (2)-2-nonenal, and (Z)-2-decenal showed the highest odor activities in the roasted nuts. These odorants, as well as several others, were previously unknown in hazelnuts. In addition, the intensely seasoning-like smelling 3,5,5'-trimethyl-2(5H)-furanone was identified for the first time as a food aroma compound on the basis of a newly developed synthetic route and NMR measurements.