Characterization and quantification of odor-active compounds in unsaturated fatty acid/conjugated linoleic acid (UFA/CLA)-enriched butter and in conventional butter during storage and induced oxidation

Dairy products enriched in unsaturated fatty acids (UFA) and conjugated linoleic acids (CLA) have a higher nutritional value and are suggested to have beneficial health effects. However, such acids are susceptible to oxidation, and off-flavors may be formed during storage. This study was aimed to compare the most important odorants in UFA/CLA-enriched butter to that of conventional butter during storage and induced oxidation. Volatiles were isolated by solvent-assisted flavor evaporation and identified by gas chromatography- olfactometry and mass spectrometry. Aroma extract dilution analysis revealed 18 odorants that were quantified by stable isotope dilution analysis. Another important odorant, 3-methyl-1H-indole (mothball-like odor), was quantified by high-performance liquid chromatography. After storage, UFA/CLA-enriched butter showed higher concentrations of pentanal (fatty), heptanal (green), butanoic acid (cheesy), and δ-decalactone (peach-like). Photooxidation of butter samples induced increases in heptanal, (E)-2-octenal, and frans-4,5-epoxy(E)-2- decenal, especially in conventional butter. The higher vitamin content in UFA/CLA samples may protect this butter from oxidation.