Characteristic flavor compounds in soy protein isolate and their correlation with sensory attributes

A molecular sensory analysis of soy protein isolate (SPI) was conducted using headspace solid-phase microextraction and gas chromatography-mass spectrometry/olfactometry (HS-SPME-GC-MS/O), along with flavor recombination and omission experiments. Twenty-six odor-active compounds were identified, with hexanal, heptanal, octanal, nonanal, (E)-2-nonenal, (E,Z)-2,6-nonadienal, (E,E)-2,4-nonadienal, and (E,E)-2,4-decadienal as characteristic flavor compounds contributing to grain husk, grassy, raw bean, tofu, oil oxidation, and soy milk flavors. The identification of these compounds in the olfactory references, combined with descriptive sensory analysis under varying concentrations, revealed a significant correlation between sensory attributes and the composition and concentration (p < 0.05). Grassy and raw bean were associated with all compounds; grain husk was linked to hexanal, heptanal, and (E,E)-2,4-decadienal; tofu was associated with octanal, nonanal, and (E,E)-2,4-decadienal; oil oxidation was related to hexanal, octanal, nonanal, and (E,E)-2,4-decadienal; and soy milk was correlated with hexanal, nonanal, (E,Z)-2,6-nonadienal, and (E,E)-2,4-decadienal. Flavor intensity generally increased with compound concentration. This study provides a theoretical foundation for the subsequent flavor enhancement of soy protein products.