Model Studies on the Effect of Aldehyde Structure on Their Selective Trapping by Phenolic Compounds

The reaction among flavor-relevant saturated aldehydes (propanal, 2-methylpropanal, butanal, 2-methylbutanal, 3-methylbutanal, pentanal, hexanal, and glyoxal) and phenolic compounds (resorcinol, 2-methylresorcinol, 2,5-dimethylresorcinol, and orcinol) was studied both to identify and to characterize the formed carbonyl-phenol adducts and to understand the differences in the carbonyl-trapping abilities of phenolic compounds. The obtained results showed that carbonyl-trapping by phenolics is selective and that the formation of carbonyl-phenol adducts depends on the structures of both the phenol and aldehyde involved. In relation to the phenolic derivative, the presence of groups that increase the nucleophilicity of phenolic carbons will increase the carbonyl-trapping ability of these compounds. On the other hand, the presence of groups that increase the steric hindrance of these positions without affecting nucleophilicity will inhibit the reaction. Analogously, the presence of branching at position 2 of the aldehyde will also inhibit the reaction by steric hindrance. All of these results suggest that the addition of phenolics to foods may change food flavor not only because of their sensory properties but also because they can modify the ratio among food odorants by selective reaction of phenolics with determined carbonyl compounds.