A compound can smell like plastic on its own yet seem fruity when smelled together with mango aroma. A 2021 study found just such a difference in the impression of a compound called 3-carene oxide.
The research aimed to identify compounds contributing to the characteristic aromas of three mango cultivars. It also explored their roles within the whole fruit’s aroma, which cannot be understood simply by smelling isolated compounds individually.
Examining three cultivars in two ways
The study used commercially available, suitably ripe Irwin, Carabao, and Nam Dok Mai mangoes. Eight assessors evaluated freshly cut fruit. Irwin was described as sweet, fruity, and lactone-like; Carabao as green and sour; and Nam Dok Mai as fruity and sweet, with sulfurous and green impressions as well.
The researchers extracted aroma compounds from 1.1 kg of flesh from each cultivar using solvent extraction, then prepared aroma concentrates by high-vacuum distillation. Two methods were used, both based on gas chromatography–olfactometry performed by three expert assessors.
One was AEDA: extracts were diluted in threefold steps, and the instrumentally separated compounds were smelled to determine the dilution at which they remained perceptible. The other was AROMATCH, which delivers aroma from freshly cut mango to the nose at the same time as each separated compound.
For the background aroma in AROMATCH, 100 g of mango flesh was cut into approximately 2 cm cubes and mixed with 10 g of a 1% ascorbic acid solution. The fruit aroma was delivered at 25°C, allowing the researchers to examine how individual compounds were perceived within it.
Shared sweet compounds and cultivar-specific features
The two analyses detected 41 odor-active compounds. Of these, 36 were identified by comparing odor, retention behavior, and mass spectra with reference standards.
In AEDA, where compounds are smelled on their own, sweet-smelling HDMF, also known as furaneol, had a high FD value in all three cultivars. An FD value indicates how far an extract can be diluted while an odor remains detectable, helping identify strong candidates for aroma contribution.
In Irwin, sweet lactones reminiscent of peach and coconut stood out. In Carabao and Nam Dok Mai, green-smelling (Z)-3-hexenal and sweet vanillin had high FD values. Compound analysis thus provided clues consistent with the overall sensory impressions of each cultivar.
A mango background can change the impression
A particularly interesting example was 3-carene oxide in Irwin. Described as plastic-like in the analysis of isolated compounds, it was described as fruity in AROMATCH, when smelled alongside the whole fruit’s aroma.
In Irwin, p-cresol likewise shifted from an animal-like impression on its own to a ripe impression against the fruit aroma. Against the Carabao background, however, p-cresol was still described as animal-like. It does not produce a ripe impression with every aroma background.
Another example was the lactone (Z)-6-dodecen-4-olide. Its FD value in Irwin was 243 by AEDA but reached 59,049 by AROMATCH, where it was perceived as contributing sweetness and body. Its role was thus detectable at a greater dilution with the fruit aroma in the background.
The ratio between those values does not mean that the mango odor became hundreds of times stronger. It compares the dilution at which a component remained perceptible under two different ways of smelling.
An isolated odor does not determine a compound’s role
In AROMATCH, γ-octalactone in Nam Dok Mai also changed from a sweet, coconut-like odor in isolation to an impression of adding body to the whole aroma. Not every compound became easier to detect, however: some had lower FD values when combined with the background aroma.
These findings suggest that mixing aroma compounds can change their detectability and quality. A compound described in unfavorable terms on its own may contribute to ripeness or distinctive character within the whole fruit’s aroma.
Three compounds were reported as newly identified in mango: 3-carene oxide, 4-acetoxy-2,5-dimethyl-3(2H)-furanone, and (Z)-6-dodecen-4-olide. They were considered important candidates for understanding Irwin aroma in particular.
The mechanisms of interaction still need testing
The study combined compound screening with evaluation against a natural aroma background. The assessor group was small, and the authors identified statistical testing of changes in detectability and quality in more people as a future task. The study did not measure interactions at odor receptors.
The authors also proposed that 3-carene oxide and p-cresol might serve as indicators of fruit ripeness, but this was not established by following ripening over time. Further tests across cultivars, maturity levels, and harvest and storage conditions are needed.
Summary
The three mango cultivars shared sweet HDMF and other compounds, while differing in features such as lactones and green-smelling components. In Irwin, 3-carene oxide, which smelled plastic-like on its own, became fruity against the fruit aroma, while animal-like p-cresol took on a ripe impression.
A molecule’s role within an aroma is not determined solely by how it smells in isolation. Considering the compounds that reach the nose together helps reveal the combinations that create mango character.
All four authors listed Soda Aromatic Co., Ltd. as their affiliation at publication. They declared that they received no external funding and had no competing financial interests.
References
Kuroki, R., Sakano, R., Hattori, S., & Morishita, S. (2021). Comparing odor-active compounds in three mango (Mangifera indica L.) cultivars by aroma extract dilution analysis and the method for evaluating odor interactions. Food Science and Technology Research, 27(1), 103–109. doi:10.3136/fstr.27.103 (Full original article)
