For comparison, sharks detect blood in water in the parts per million range (which itself is already super impressive.)
https://en.wikipedia.org/wiki/Geosmin
https://www.acsh.org/news/2018/07/28/geosmin-why-we-smell-ai...
https://glebekitchen.com/chicken-biryani-indian-restaurant-s...
Yes, about half the page is "story" but it's actually got some quite important information about technique, it's not all waffle about the author's grandmother's favourite cake plates.
Everything on that site is good. Read up on "British Indian Restaurant Technique" and you'll nail all your favourite curries first time - the garlic ginger paste and onion gravy are essential.
In London, the most authentic biryani (by which I mean closest to the original style, before other regions adapted it to their own tastes) is Awadhi/Lucknowi biryani. You can find a great version at Biryani Kebab & Chai in Soho, and another solid option is at TH@51 Restaurant & Bar at St. James’ Court, which is owned by Taj Hotels ,.. a very old school Indian hotel group ...
1. The distinctive scent, caused by geosmin, which accompanies the first rain after a long, warm, dry spell. 2. The yellow organic oil that yields this scent.
From Wiktionary: "The term was coined by Australian scientist Richard Grenfell Thomas in 1964 for the article “Nature of Argillaceous Odour”, co-authored by Isabel Joy Bear and published in the journal Nature."
Some nuggets from the paper:
> There is some evidence that drought-stricken cattle respond in a restless manner to this 'smell of rain' which may drift with the wind for considerable distances.
> We have learned from the Indian Standard Association that the production and concentration of argillaceous odour from baked clay have been, for many years, the basis of a small perfumery industry centred near Kannauj, some 80 miles west of Lucknow, U.P., India. Baked clay disks, exposed there under the open sun during the hot summer months of May and June, are collected before the wet season and are steam-distilled and the vapours containing the odour and associated products are absorbed in sandalwood oil. The perfume so obtained is known as 'matti ka attar', which may be translated as 'earth perfume'.
> The diverse nature of the host materials has led us to propose the name 'petrichor' for this apparently unique odour which can be regarded as an 'ichor' or 'tenuous essence' derived from rock or stone. This name, unlike the general term 'argillaceous odour', avoids the unwarranted implication that the phenomenon is restricted to clays or argillaceous materials; it does not imply that petrichor is necessarily a fixed chemical entity but rather it denotes an integral odour, variable within a certain easily recognizable osmic latitude.
I don't know if it is just that it is an Australian thing, but certainly my friend group would all just say "petrichor" for this scent.
The Australian's who coined the term specifically credited Indian perfumers for their matti ka attar; they had collected and distilled it for centuries before (western?) science investigated.
Like lots of scents, the fresh versus the preserved are different. Petrichor has a sharp ozone smell, that does not persist when preserved, where it ends up with an earthier smell afterwards.
Apparently humans can smell this in parts-per-billion quantities. Certainly once you become attuned to it (if you live in the country) you can "smell rain" when it's well over the horizon.
For oud, another divisive note, you have people like "ughhh this smells like shit I hate it" and others "yeeeah this smells like shit I love it", but for rainy scents you have people getting entirely different perceptions
Otherwise known a one litre! Assuming that they mean US Customary gallon.