| Selective binding of flavor compounds by soy proteins can lead to persistence of off-flavors and/or flavor imbalance in formulated soy products. Currently, there is limited information concerning binding of volatile flavor compounds by soy proteins in low-moisture foods.; An inverse gas chromatographic (IGC) method was developed to investigate flavor-soy protein interactions in low-moisture food systems. Influence of flavor compound chemical structure and environmental relative humidity (RH) on binding of volatile flavor compounds to dehydrated soy protein isolate (SPI) was evaluated. Ten volatile probes representing compounds from several different chemical classes were included in this study, and their interactions with SPI under several RH levels (0, 8, 30, 40, 50%) were measured. Binding of selected butter flavor compounds by soda wheat and soy crackers was evaluated by IGC, solvent extraction and sensory evaluation techniques.; IGC provided rapid and precise measurements of thermodynamic and sorption data. Flavor compound chemical structure greatly determined its binding potential to SPI. Weak binding of hydrocarbons to SPI was attributed to nonspecific van der Walls dispersion forces only, while stronger binding exhibited on those more polar compounds (ester, ketone, aldehyde, alcohol) might be ascribed to both specific and non-specific interactions (hydrogen bonding, dipole and van der Walls dispersion forces). Interaction potential of polar flavor compounds with SPI was greatly impaired by adsorbed water in the extremely low humidity region (approaching 0% RH); while their binding strengths with SPI were not significantly affected by further water uptake in the 30∼50% RH region. Stronger interactions with the crackers at 15% RH were observed for gamma-butyrolactone and butyric acid, possibly due to the involvement of stronger hydrogen bonding and/or ionic forces, than for diacetyl and hexanal. Presence of soy proteins did not affect binding of diacetyl and hexanal, but increased binding of gamma-butyrolactone and butyric acid. Solvent extraction data agreed with IGC results in that retention/binding of butyric acid was higher in the soy cracker, while binding of diacetyl to the two crackers did not differ. However, sensory results showed that headspace diacetyl or butyric acid aroma intensities of the two crackers were not significantly different. |
