Key Aroma Compounds in Roasted In-shell Peanuts

An investigation by using an aroma extract dilution analysis (AEDA) of the aroma concentrates made from freshly roasted in-shell peanuts and stored peanuts revealed a total of 43 key aroma compounds, including 8 newly identified compounds in peanuts. Among them, 2-isobutyl-3-methoxypyrazine, exhibiting an earthy note, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone, exhibiting a caramel-like note, were detected with the highest flavor dilution (FD) factor of 4096 in the fresh peanuts, followed by 3,5-dimethyl-2-ethylpyrazine, exhibiting a nutty note, as having the next highest FD factor of 1024. A quantitative analysis of the key aroma compounds having high FD factors in the fresh peanuts and stored peanuts revealed that 2-methyl-3-furanthiol, 2-acetyl-1-pyrroline, 2-propionyl-1-pyrroline, and 3,5-dimethyl-2-vinylpyrazine significantly decreased during storage, while methyl 2-methyl-3-furyl disulfide, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, and 2-methoxy-4-vinylphenol significantly increased. The sensory experiments revealed that the fresh peanuts presented strong roasty/meaty, popcorn-like, and nutty notes, as well as moderate spicy/burnt and caramel-like notes, whereas the stored peanuts presented significantly weak roasty/meaty and popcorn-like notes and a significantly strong spicy/burnt note. Based on the comparative AEDAs, the quantitative analysis, and the sensory analysis, it was concluded that the freshly roasted peanut aroma comprised the significant contributions of 2-methyl-3-furanthiol exhibiting a roasty/meaty note, and of 2-acetyl-1-pyrroline and 2-propionyl-1-pyrroline exhibiting a popcorn-like note, and the lesser contribution of 2-methoxy-4-vinylphenol exhibiting a spicy/burnt note. In particular, 2-methyl-3-furanthiol, which was only detected in the freshly roasted peanut aroma concentrate, might be an essential component describing the freshness of the roasted peanut aroma by its diffusive roasty/meaty note.