This is in India. I purchase fresh meat (chicken/beef) from the shop and sometimes keep it in the freezer until I'm ready to pressure-cook it on some other day.
I noticed that after thawing it in the fridge for a day, there was a red liquid that collects at the bottom of the container. I assumed the freezing process squeezes the meat and that causes the blood in it to flow out (silly me). This answer says it's myoglobin. Wikipedia says...
The released myoglobin is filtered by the kidneys but is toxic to the renal tubular epithelium and so may cause acute kidney injury
...but I'm hoping that's myoglobin in the bloodstream, and not a part of digestion.
I searched for research papers to check for safety of consuming myoglobin, and came across this paper that says...
As internal cooking temperature increased soluble myoglobin content decreased with a corresponding increase in percent myoglobin denatured. Percent myoglobin denaturation values ranged from 0 (raw chops) to 77.30% in mutton chops cooked to 79 °C internal temperature.
Couldn't find much else on the safety aspect, but since it gets denatured, I'm assuming it'd be safe.
However, all this literature appears to refer to the myoglobin within the meat that gives it a flavour and juiciness. What about the liquid at the bottom of the container that contains myoglobin? Is it useful to retain it or is it better to just drain it away since it is separated from the meat already?