[EvaH (OP)]

We've had this question in from Neerav:

I have a question as to how coffee granules dissolve so well compared to soup-in-a-pack, for example. The difference is amazing, coffee dissolves with minimal or no stirring!

We'll be answering this question next week on our show, but do you have an answer to share?

[Bogie_smiles]

I have been a coffee drinker since I was a teenage, and if brewed coffee was not available, instant was fine. Instant is brewed coffee that has been dehydrated, and so adding water brings it back to its liquid state; a perfectly natural outcome. There is probably a minimum amount of water need to dissolve all of the graduals, but if you add enough hot water to dissolve them all, you can then control the strength by controlling the amount of water you add beyond that point.

[chiralSPO]

I have a question as to how coffee granules dissolve so well compared to soup-in-a-pack, for example. The difference is amazing, coffee dissolves with minimal or no stirring!

There are a few factors involved:

The inherent solubility of thee compounds in instant coffee is relatively high (compared to the amounts of stuff). Soup mixes will contain significant amounts of fats and other lipophilic/hydrophobic compounds (which melt and float in the soup, rather than dissolving).

The instant coffee grounds have quite a bit of exposed surface area, and I would guess that there might even have been a significant investment in engineering the particles to dissolve just so.  (if you could invest $5M once to figure out how to make your coffee dissolve 20% faster than your competitors' for only a 0.2% increase in production cost, it could well be worth it!)

[Bored chemist]

I would guess that there might even have been a significant investment in engineering the particles to dissolve just so.

Some of us are old enough to remember the transition from powdered to granulated instant coffee.

It may also help that essentially everything in instant coffee is soluble in water whereas soups contain stuff like starch- which forms a colloidal suspension.

[Bill S]

Some of us are old enough to remember the transition from powdered to granulated instant coffee.

But none of us is old enough to remember the introduction of instant coffee.  Britain, 1771; US, 1851

[Bored chemist]

Some of us are actively trying to blot out any recollection of this stuff.
https://en.wikipedia.org/wiki/Camp_Coffee

[EvaH (OP)]

Asked and answered! And you can find the answer here https://www.thenakedscientists.com/podcasts/question-week/why-does-coffee-dissolve-so-fast

[Anad Rutner]

There is really no difference between instant coffee and instant oatmeal. They have both been pre-brewed/-cooked and dehydrated.  It takes but a few moments for the coffee to dissolve as the granular size is smaller than oatmeal which takes a minute or so.

[Bored chemist]

There is really no difference between instant coffee and instant oatmeal.

There really is a difference.