Sensory-directed flavor analysis of key odorants compounds development of French fries and oils in the break-in, optimum and degrading frying stage

The flavor is a decisive sensory characteristic that determines the popularity of French fries（FFs）. During high-oleic rapeseed oil（RO） frying, the flavor development of FFs showed three noticeable stages including break-in（3.5%–7.5% of total polar compounds（TPC））, optimum（7.5%–22.18% of TPC）, and degrading stages（above 22.18% of TPC）. Further, in order to distinguish the key aroma compounds in each stage, the FFs prepared in RO at TPC of 3.5%（FF4）, 14.5%（FF15）, and 26.96%（FF27） and their relevant oils（RO4, RO15, RO27） were selected for sensory-directed analysis. The results revealed that the FF4 had low contents of（E,E）-2,4-decadienal（deep-fried odor） which also caused lower sensory score in FF4 sample. The higher contents of（E,E）-2,4-decadienal in FF15 induced its higher deep-fried odor. The FF27 had higher hexanoic acid（sweaty odor）, heptanoic acid, nonanoic acid, benzene acetaldehyde（stale odor）, and trans-4,5-epoxy-（E）-2-decenal（metallic odor） compared with FF4 and FF15, thus leading to the undesirable flavor of FF27. Moreover, the decrease of 2,5-dimethylpyrazine and 2-ethyl-6-methyl-pyrazine in FF27 induced the lower roasty flavor, which may also lead to the decline of the sensory score. Similarly, the higher contents of（E）-2-undecenal, hexanoic acid, heptanoic acid, and nonanoic acid in RO27 lead to increase its rancid score and thus lower the sensory score.