I want to have a story where my character's find them selves on earth many thousands of years after an asteroid killed off most of life on earth. They have been in a bunker along with many other survivors. They where kept alive through cryogenics and as that tech took most of the budget in the making of these bunkers there was very little other supplies provided. When they come up life has returned and is flourishing with an abundance of food. However, some foods are poisonous and it can be very hard to tell which is edible and which will require processing.
My question is: How could people determine if a food is edible or not without risking death in the process? Ideally this process could be repeated on a poisonous food as they experiment on it to find a way to process it into an edible food.
Possible fall-backs -A process that can turn any food edible (this may not be possible as some process make some plants edible while it makes other worse) -A process to extract the essential nutrients that plants would provide through other safer means. Ideally without the need of technology to be brought along.
Important notes that may help: -humans have bitterness as a sense to detect poison but it is not 100% accurate now and would probably be worse in the future due to further evolution of plant poison. -Hunter Gatherer's used a process of having a little bit of anything to avoid reaching a critical mass of poison. This is a very simple process however it is not safe and could lead to death however this may be the starting ground for a valid process.