I'd like to experiment with freeze drying food but the only equipment I own, is a vacuum pump+chamber and an old freezer I wouldn't mind drilling to run a vacuum pipe inside.
However an important point is to flash freeze the food, otherwise I would lose much benefit of the freeze drying process. So, I wondered if I could have a good enough result by immerging the food (in a plastic bag) in water+salt/antifreeze solution at -18°C or lower.
The reason of choosing this temperature, is that I can produce it (or even lower e.g. -21°C, -24°C) with a good freezer - no need for special equipment. And the reason for choosing water, is it's massive thermal inertia. So the question is : What kind of solution would give me the best result (As much as possible, with the lowest toxicity risk with the lowest toxicity, for the antifreeze product). I know that I can get something around -21°C with normal kitchen salt, but are there better solutions without loosing too much of my water's thermal inertia ?