Characterization of Citrus Aroma Quality by Odor Threshold Values

Limited odor unit (Lo) can be used to characterize aroma quality and can be expressed by an odor unit like equation. The Lo value is an index of the significance of each aroma component at the concentration of volatile oils (ppm) diluted below the threshold level. The aroma intensity (Lo) of each aroma component is expressed by dividing the concentration of individual components at the threshold level of the volatile oils (Cr), by its detection threshold or recognition threshold (Tc). For this equation, we examined which was the most suitable, the detection threshold or the recognition threshold as the Tc value. This olfactory measurement is proposed as an objective evaluation method for food aroma quality. It was found that limonene contributes to the characteristic aroma as the base note. Limonene, linalool, and octanal were shown to be essential for the characteristic aroma. The usefulness of Lo values for the characterization of the aroma of Citrus sinensis OSBECK, cv. Shiroyanagi, was shown by the fact that a mixture of 11 compounds selected by this method (using the detection threshold as Tc) - limonene, linalool, octanal, decanal, dodecanal, geranial, neral, myrcene, α- and β-sinensal, and citronellal -duplicated the aroma of navel oranges very closely. Thus, Lo values using detection thresholds were found to be useful for sensory evaluation of the character impact compounds in navel oranges.