If you love the smell of onions in the morning, then allow us to recommend a slice of durian – a tropical fruit that remains very popular in southeast Asia despite its pungent oniony aroma. Knocked off their feet by the stench, a group of researchers from the German Research Center for Food Chemistry have attempted to quantitate the chemicals that account for the unappetizing aroma and then simulate that aroma (1)...
“My first trip to the tropics took me to Chanthaburi Province, one of the major growing regions for tropical fruits in Thailand, and I was fascinated,” says Martin Steinhaus, Group Leader of Aroma Chemistry. “Among the huge variety of different flavors, that of the durian is exceptional; not only because of its strength, but also because of its extraordinary combination of fruity and oniony odor notes. When I was choosing a topic for a new PhD student, Jia-Xiao Li, I decided it was time to crack the puzzle.”
For the analysis, they used what Steinhaus describes as the “workhorse” of aroma research: gas chromatography-olfactometry (GC-O). “The volatiles, previously isolated by mild approaches to avoid deterioration of sensitive compounds and artifact formation, are separated by GC, and the column effluent is split into two parts, one directed to a detector such as an FID or an MSD, the other one directed to a heated exit serving as sniffing port,” says Steinhaus. “A panelist places his nose above the sniffing port and identifies the odor-active compounds among the bulk of odorless volatiles in the chromatogram.”
They detected a total of 44 odor-active compounds in the durian pulp (2), and ranked their odor potency using an approach known as aroma extract dilution analysis (3). After breaking down the chemical composition of the fruit’s unique odor, the team attempted to recreate it, and were surprised to find that only two potent compounds were required. “Typically, 10 to 20 compounds are required to satisfactorily mimic the aroma of a food, but in this case, model experiments showed that a simple binary mixture consisting of ethyl 2-methylbutanoate and 1-(ethylsulphanyl) ethane-1-thiol in their natural concentrations was able to mimic the typical aroma of durian,” says Steinhaus (1).
And how did the team find working with the world’s smelliest fruit? “It is not my favorite fruit, but I wouldn’t say it is disgusting either,” Steinhaus says. “And to be honest, if you work in the field of odor-active food compounds, you get used to strong and unpleasant smells! Moreover, the benchwork was mainly done by Jia-Xiao Li, who is a big fan of the fruit. The problem was much bigger for his lab mates!”
- JX Li et al., “Insights into the key compounds of durian pulp odor by odor quantitation and aroma simulation experiments”, J Agric Food Chem, 65, 639-47 (2017)
- JX Li et al., “Characterization of the major odor-active compounds in Thai durian (Durio zibethinus L. ‘Monthong’) by aroma extract dilution analysis and headspace gas chromatography-olfactometry”, J Agric Food Chem, 60, 11253–11262 (2012).
- P Schieberle, W Grosch, “Evaluation of the flavour of wheat and rye bread crusts by aroma extract dilution analysis”, Z Lebensm Unters Forsch, 185, 111-3 (1987)
A former library manager and storyteller, I have wanted to write for magazines since I was six years old, when I used to make my own out of foolscap paper and sellotape and distribute them to my family. Since getting my MSc in Publishing, I’ve worked as a freelance writer and content creator for both digital and print, writing on subjects such as fashion, food, tourism, photography – and the history of Roman toilets.
