Effect of Flavor Compound Chemical Structure and Environmental Relative Humidity on the Binding of Volatile Flavor Compounds to Dehydrated Soy Protein Isolates

Influence of flavor compound chemical structure, including functional group and stereochemistry, and environmental relative humidity (RH) on the binding of volatile flavor compounds to dehydrated soy protein isolates (SPIs) was evaluated by inverse gas chromatography. Binding of selected volatile flavor compounds differed slightly between SPIs of different origins. Results showed that the flavor compound chemical structure greatly determined its binding potential to SPIs. Binding of nonpolar flavor compounds (hydrocarbon) to soy proteins was attributed mainly to nonspecific van der Waals dispersion forces and was not affected by adsorbed water. The more polar flavor compounds (ester, ketone, aldehyde, and alcohol) exhibited both specific (hydrogen bonding, dipole forces) and nonspecific interactions, and their binding with soy proteins was greatly impaired by adsorbed water in the extremely low humidity region (approaching 0% RH). Further water uptake in the 30 to 50% RH region did not significantly affect the binding of polar compounds, although sorption of alcohol compounds (when present at high levels) further increased. Keywords: Soy protein isolate; volatile; flavor compound; flavor binding; chemical structure; relative humidity; inverse gas chromatography