Short and unsweetened: what happens if I make H&S with cold water (and wait for the same time for it to settle)? Is boiling water required to kill germs, does it help the digestion of vitamins and minerals, or else?
I think dry food rehydrates better with hot water
With the pasta ones at least - heat breaks down the starch molecules and denatures the proteins in the pasta. This makes the molecules digestible, but it also makes them taste better. The denaturing of glutens and other proteins in the pasta causes a change in the texture and makes it more palatable. I would imagine making it with cold water would make it virtually inedible.
You’re going to end up with super crunchy pasta and the powder probably won’t be properly dissolved (I’m not sure exactly as I haven’t tried this).
Hot water is the final cooking stage, it’s a quality issue more than a safety one.