We don't know why some things smell the way they do. What do you mean we don't know what a walnut smells like? You heat it up, run it through a gas chromatograph, and look for the spikes. Right? Not so fast. For some things, like walnuts, we didn't know how to recreate its odor without an actual walnut. Cannabis too; we all know the most easily identifiable characteristic of cannabis is it's stinky skunky odor, and yet we don't know where it comes from, down to the single molecule.
The problem is that some odors that we identify as distinctive, indivisible, or unique are actually more than one molecule; the secret is in the ratio. In other words, the secret ingredient in the secret sauce is the recipe itself, not the ingredient:
Researchers isolate key compounds in the aroma of walnuts
Jun 2023, phys.org
As the team shows for the first time, the typical walnut aroma is created by the combination of two odorants that are present in the nuts in roughly a one-to-one ratio. The first substance is sotolon, which smells like Maggi Seasoning sauce and which, as a single component, characterizes the aroma of lovage, for example. The second compound is called (2E,4E,6Z)-nona-2,4,6-trienal. It is known from oat flakes and is responsible for the typical odor there.
British scientists had already olfactorily characterized numerous volatiles from walnuts about 50 years ago. However, none of the compounds they found had a specific walnut note. Thus, the researchers concluded that the characteristic walnut aroma is based on a combination of odorants. Despite this finding and further experiments, however, it had still not been clarified which odor-active compounds are decisive for the aroma of walnuts.
Not the components but the ratios of components -- "In our sensory tests, the walnut note intensified even further when we increased the natural concentrations of both odorants up to tenfold," reports Christine Stübner, a doctoral student who worked on the study. "However, it was important to maintain the one-to-one ratio," she continues.
(By the way, what's the purpose of all this -- based on these findings, new breeding strategies can now be developed to improve walnut aroma.)
Finally, Instant Walnuts: Put a tablespoon of oatmeal in a glass, add a few drops of the well-known Maggi Seasoning seasoning sauce, shake it a bit and smell the mixture. (Maggi Seasoning smells like sotolon, fenugreek, hot transmission fluid.)
via Leibniz-Institut für Lebensmittel-Systembiologie (Inst for Food Systems Biology) -- Christine A. Stübner et al, Sotolon and (2E,4E,6Z)-Nona-2,4,6-trienal Are the Key Compounds in the Aroma of Walnuts, Journal of Agricultural and Food Chemistry (2023). DOI: 10.1021/acs.jafc.3c01002
A closer look at the compounds and molecules involved in giving cannabis its unique scent
Nov 2023, phys.org
(I was looking at the authors for Avery Gilbert, but no. I think some rec ognition is in order; he was the first to conduct smell research on cannabis.)
Using mass spectrometry, gas chromatography and flame ionization detection, researchers found that a molecule called 3-methyl-2-butene-1-thiol (321MBT), along with other volatile sulfur compounds (VSCs), appeared to play a prominent role in odor production. 321MBT is the same molecule that gives warm beer and skunk spray their distinctive smells.
via terpene distributor Abstrax Tech: Iain W. H. Oswald et al, Minor, Nonterpenoid Volatile Compounds Drive the Aroma Differences of Exotic Cannabis, ACS Omega (2023). DOI: 10.1021/acsomega.3c04496
Research team identifies human odorant receptor for 'horse stable' odor, with implications for food testing
Aug 2023, phys.org
Para-cresol (4-methylphenol) is an aromatic compound with a strong horse stable-like odor, it is formed during the microbial degradation of certain amino acids, but also during thermal degradation processes, it's also a characteristic odorant in whiskey and tobacco.
- The OR9Q2 receptor was the only one that responded to physiologically relevant concentrations of the substance.
- Conversely, 4-ethylphenol was the only one of 176 aromas able to significantly activate the receptor. (and that's called being highly selective).
- "The receptor fills a gap in the recognition spectrum of the phylogenetically older human odorant receptor OR2W1, which detects a wide range of structurally different odorants, but not para-cresol."
via Leibniz-Institut für Lebensmittel-Systembiologie aka Leibniz Institute of Food Systems Biology at the Technical University of Munich: Franziska Haag et al, The multi-faceted food odorant 4-methylphenol selectively activates evolutionary conserved receptor OR9Q2, Food Chemistry (2023). DOI: 10.1016/j.foodchem.2023.136492
