Characterization of the Key Odorants Causing the Musty and Fusty/Muddy Sediment Off-Flavors in Olive Oils.

Microbial spoilage of olive fruits is among the most frequent reasons for two types of off-flavors in olive oils, assigned as musty and fusty/muddy sediment. To characterize both off-flavors on a molecular level by means of the sensomics approach, the key aroma compounds in a premium extra virgin olive oil (1) eliciting the typical sensory properties were compared to those identified in two off-flavor olive oils obtained from the International Olive Council (IOC). A comparative aroma extract dilution analysis (cAEDA) followed by identification experiments revealed 53 odorants in the musty reference olive oil (1) and 48 odorants in the fusty/muddy sediment one (1). Odorants, differing in flavor dilution (FD) factors or showing a high FD factor in at least one of the olive oils, were quantitated by stable isotope dilution analysis (SIDA), followed by the calculation of odor activity values (OAVs; ratio of concentration of an odorant to the respective odor threshold in odorless refined sunflower oil). Aroma recombination and omission experiments revealed 13 key aroma compounds in 1 and 12 in 1. To demonstrate the importance of volatile phenols, 10 phenolic smelling odorants were quantitated in further 13 extra virgin olive oils, in 3 musty and in 13 fusty/muddy sediment defective olive oils, and in 8 olive oils with other off-flavors. Both sensory defects could successfully be discriminated from extra virgin olive oils by applying either a principal component analysis or a hierarchical cluster analysis. Considering possible reaction pathways and all results obtained including Pearson coefficients between the odorant concentrations and the intensities of the defects, specifically 2-methoxyphenol and 4-ethylphenol were proposed as marker compounds for the quality assignment of both types of off-flavors induced by microbial spoilage among the identified key aroma compounds.