I am making duck confit this weekend and will refrigerate it. I am curious though; what are the concerns for leaving it in a cool room?

Question

I've made duck confit many times before and used it fresh. This time, though, I'd like to try to age it in the fridge a bit to see if I notice a difference.

To do this I've purchased some earthenware pots. I will salt the duck legs for 24 hours in the fridge. Then I will remove excess salt, and place them in a 230F oven, completely submerged in fat, for about 4 hours.

It seems safe to assume that all of the duck will spend at least 2-3 hours near boiling temperature. It follows that this would effectively sterilize it. This got me thinking... If I were to leave it in the oven, undisturbed in a now sterilized oven, to cool until the fat solidifies and then simply leave it in my unfinished basement (which is constantly around 60-65F) how could bacteria realistically get a foothold and create unsafe food? I come across many posts claiming this is not food safe, but none of them explain any vector for spoilage and it seems you have to take them at face value to "be safe".

To be clear I'm not advocating for being lax on food safety, I'm just curious about the science behind why this could be hazardous.

Answer 1

2-3 hours at an unknown temperature, which you assume (but cannot prove) that is 'near boiling' will not sterilize it.

First, to kill all spores which might already be present, 100 C is not sufficient. You need to spend a certain number of time at a certain internal temperature above 100*, and that temperature will have to apply to all parts of the meat - I don't have exact numbers on hand, and the tables for canning are for the whole process, not just the "sterilizing" part of it. Basically, for any process that sterilizes, you have to prove that, when executed repeatedly, it always ensures the minimum time at the minimum temperature.

Second, your pots are not sealed canning jars. Both in your oven (which is also not airtight and will permit the entry of bacteria after it cools) and in your basement, the fat layer will have contact with bacteria. Now, pure clarified fat is not actually bacteria-endangered (that's why oil is shelf-stable), but the fat in confit contains some small percentage of meat solids and meat juices, which, in the worst case (and food safety always assumes the worst case) are sufficient to give bacteria a foothold.

* to go down to the nitty-gritty, there is a certain trade-off, you can spend shorter times at higher temperatures, or longer times at lower temperatures. But specifically for spore-forming bacteria, there is a minimum temperature, below which even infinite times won't give you safety.

Answer 2

Confit is a preservation method that has been around longer than refrigeration. In fact, the French word it derives from means to preserve. The process is fairly straight-forward. First, salt/cure the product so that the surface is no longer hospitable to bacteria. Then, submerge in fat (for proteins) and cook (usually at a temp of 180 to 200F (82 to 94C). In fact, the protein itself probably never gets above 200F (94C). While cooking, the protein usually releases liquids (but not enough to dry out the product). This liquid sinks to the bottom, and when cooled, sort of solidifies. It is known as confit jelly, and is delicious. It can be added to sauces. The entire vessel of confit should be cooled. Then for long term storage, the protein should be removed from the cooking fat, placed in a storage container, and covered in pure fat (removing the confit jelly). The idea of confit is to first cure the product (removing the bacterial risk). Then control the temperature (with the fat mediating the environment) for gentle cooking. Finally, storing covered in pure fat, to create an oxygen barrier, again removing the bacterial risk. If you cured correctly (right amount of salt for the right amount of time), cooked correctly, and have now submerged in "clean" fat. There is no reason to believe that it will not be safe at "cool room temp" for a short time. After all, those are the conditions that the process was initially used for. However, you will increase storage time and safety with refrigeration. You an further decrease risk by using a small amount of "pink" salt.