[Second] <...> Now to the crux of matter concerning those quotes. It's simplest to explain what I'm on about by way of a real example. A couple of years ago, I helped a colleague move the contents of his factory to a new location and we needed drums to store various oils and cutting lubricants from his machine tools. 20-litre ones were too small, 210ltr/44 imp. gal too big, so we settled on using 100 litre ones and the only place we could get them from was a supplier/distributor of synthetic musks, aka SMs, (as used to perfume detergents etc.) who supplied used empties. Each drum still contained a residue of between 300 to 500 ml (due to the bung lip emptying problem) and yours truly was far too curious to let interesting chemicals like these ones escape without further examination, so I saved them.

The drums still had their CAS numbers, IUPAC info/chemical formula and InChI identifiers so I knew exactly what I had. I ended up with a wide collection of about a dozen different chemicals whose structures ranged across the three most common musk types: nitro/xylene/ketone-like, macrocyclic ketones and polycyclic/galaxolide-like musks.

You can imagine what the old factory smelled like while I emptied out the drums, it stank to high heaven and you could still smell the musks way down the street (not surprising really, given that the human olfactory detection threshold for some of them is supposedly in the ng/l range). (Incidentally, whilst I can't immediately recall the exact details, the older-type nitro variety are potentially explosive, these ones were modern variants (isomers, enantiomers or whatever—I can't remember), thus that wasn't an issue—noticeably, the drums didn't have any hazard warnings to that effect.)

When I commented to my colleague to the effect that I hope we don't get complaints about the stink from those in nearby buildings he retorted "what stink?", he then stuck his nose in the open bung hole of one of the drums and said "it only smells a bit oily to me". This immediately rang alarm bells, as I was aware that he had no difficulty smelling other things.

This led me on a quest to understand more about synthetic musk chemistry and to find out why a comparatively large percentage of the population cannot smell the stuff because of minor genetic differences in their makeup (methinks that must be a problem for the marketing departments of soap powders)! A month or so later I put a small selection of the chemicals into the smallest type of Tabasco sauce bottles, 60 ml, (as a chilli eater I've lots of empties) and took them along to one of the regular social nights I attend. The group is about 20 in size and we do nothing other than wine, dine and yak BS well into the evening. Furthermore, many are rather opinionated about wine and continually argue over which wine is best on the night (of which there may be up to six or more bottles thereof). That said, I've never seen a bottle there that cost more than a low two-figure sum let alone a Bordeaux first growth! Unsurprisingly, knowing my friends, there are two chemists in the group.

Testing the musks out on this 20-something sample, I found that roughly 30% could not detect the musk odour and it included one of the chemists (somewhat to his chagrin), whilst a reasonable percentage of those who could detect it complained that the smell was so overpowering that it would put them off their food. Now that's a contrast!

This brings me back to the human calibration matter and your comment "The simple examination was tough enough for me, and that only increased my respect for the really skilled people." Absolutely, as per the highly respected cellar owner in my previous comment. So where does this leave us? Clearly human perception of odours is highly variable. This quote from an article† that I read when researching the musks sums it up reasonably well:

" Human perception of the odour environment is highly variable. People vary both in their general olfactory acuity as well as in if and how they perceive specific odours. In recent years, it has been shown that genetic differences contribute to variability in both general olfactory acuity and the perception of specific odours. Odour perception also depends on other factors such as age and gender."

This brings me back to your other points:

"At the industrial level, the tasting is also done alongside and correlated with quantitative scientific analysis."

Right, that correlation is something I want to learn more about but I'm not expecting you explain it. Knowledge of it is important to sort the crap and BS out of 'unscientific' wine tasting—and for that matter—many other tasting experiences, disagreements, arguments, etc., such as why some like truffles and others do not, or why as a kid I'd eat all green vegetables including spinach, broccoli and cabbage whilst there'd be a screaming match from a sibling when given them. Similarly, at the age of six why I stopped my mother diluting my tea with hot water after she poured it. Then, within a week of that, I demanded that she stop ruining my tea by adding milk and sugar to it—right, I've drunk it black ever since.

Coming back to the musk matter, I've had many a discussion over characteristics of various wines with my chemist friend (the one who cannot detect the musk odour) and we rarely agree, each coming to a different conclusion over one characteristic or another is best. This led me to the inevitable conclusion that his failure to detect the musk may make him more capable of detecting other types of odours than me and vice versa. I've never read any surveys or statistical correlations of the population such as those who can and can't detect musk versus their perceptions of various different wine characteristics (but then I've never done a proper search of the literature either).

Thus, I'd imagine what you say below perhaps ought to be able to enlighten us (if specifically applied to the matter):

"The lab I worked in ran each batch through GC-FID (basic stuff), headspace-sampling GC-FID (volatile aromatics), alongside a battery of additional physical and chemical analyses (too many to list here, there are at least 20, the big brewers take product quality and safety really seriously)."

…And so should this:

"And we had GCMS and LCMS systems and other more detailed tests as options on demand to test more obscure stuff like metal content (for making Marmite yeast extract where iron levels are important, apparently)." Altogether, I reckon your approach was pretty comprehensive, there's not much left to chance. It's belts and braces level stuff.

Over to you! Have I been living under a mushroom or just ill-informed, or could there actually be a complex relationship between one's ability or inability to be able to detect musk and the ability to detect or not detect other volatile aromatics that, say, are in wine and other substances? Essentially, do you know anything about this, if so is there a well-understood position or are we into new territory?

Given my experience and 'straw poll'/small sample, from my perspective there's a tiny modicum evidence that seems to suggest it. Moreover, given the enormous complexity of the matter and the complex non-linear interrelationships between all the various 'components' I'd not be surprised if there were. (As from my previous experience with other complex systems, almost inevitably new tertiary effects arise. The trouble is that one never knows when or where they'll turn up and what form they'll take—that is until they do.)

Other matters will have to wait for now.

† https://bmcneurosci.biomedcentral.com/articles/10.1186/1471-...