Modeling the sensory impact of defined combinations of volatile lipid oxidation products on fishy and metallic off-flavors.

The volatiles (E,Z)-2,6-nonadienal, 1-penten-3-one, (Z)-4-heptenal, and (E,E)-2,4-heptadienal were added to milk containing 1.5% fat according to a central composite design, to evaluate the individual and combinatory effects of these volatiles on sensory properties. The milk samples with added volatiles were subjected to sensory descriptive analysis for fishy and metallic off-flavors. The data were analyzed using partial least-squares regression and multiple linear regression to develop mathematical models. The models revealed significant main effects of (E,Z)-2,6-nonadienal and 1-penten-3-one and highlighted the importance of two-factor interactions for contribution toward off-flavors. The results suggest that (E,Z)-2,6-nonadienal and 1-penten-3-one could be useful markers for fishy and metallic off-flavors in fish oil and fish oil enriched foods. Within the addition levels of the volatiles there was a curvature effect of (E,Z)-2,6-nonadienal, a compensatory effect of (Z)-4-heptenal and (E,E)-2,4-heptadienal, and a synergistic effect of (E,Z)-2,6-nonadienal and (Z)-4-heptenal in the development of fishy off-flavors.