For instance if I boil chicken, how much protein will dissolve into the water?
(If you can put it like that)
> For instance if I boil chicken, how much protein will dissolve into the water?
That scum you see floating on the top of the water when you boil chicken (or make stocks, soups etc) is mostly denatured protein.
Most land animals have relatively little water soluble protein so losses are fairly minimal, according to USDA 51g/lb of protein in raw chicken and 49g/lb when its stewed or simmered. That ~4% loss is not worth tracking, its well within the existing margin of error for meat nutrition.
IIRC from my sous vede reading when cooked above 160°F-ish muscle fibers start to contract and squeeze out the water resulting in dry hockey pucks. Brazing is long cooking times eventually breaking down the proteins an softening the meat. The cooking fluid will have dissolved proteins, but unless you cooking it down for hours and hours you’re good. Also you can always drink the broth if you don’t season it with too much salt.