How Long can mixed protein and water be kept before it goes rancid

To save time, I was wondering if I could mix my protein in the morning and then maybe keep it in the frig throughout the day. I don’t know how long it would be good however. I plan on mixing hot water(not very much 4oz for 60g of protein) and milk protein isolate. Once this cools it takes on a solid cookie like formation that is easy to consume. However I don’t know how long it would take before this would go bad. How long could I store it in the frig. I would assume that this hot water would also speed up the process of oxidation. I could vaccum seal each serving if neccesary.
Thanks
I know this might seem like alot of work, but I think it will save me alot of time in the long run. Just trying to make things as effecient as possible

I used to prepair my Whey mixed with Milk ( non fat milk ) and sometimes i store in frig for about 5 to 6 hours and the taste still good as the composition. But without frig, i believe you can´t wait for more than 2 hours ( of course, it depends a lot of ambient temperature ).

i think how long you can wait depends on the quality of the ingredients. ive seen information that after 15 minutes in water, protein powder will start to denature. it may still taste fine, and it may smell fine but its potency will start to decline. if you want full pop for your dollar, mix it and drink it right away.

nightmare