Second question: I was rendering lard the other day, and was reading the recent sous-vide-style chicken broth thread, and wondered if sous-vide would be a good way to render lard and other fats? Theoretically the fat would just melt off of the skin, membrane, etc. Less clean up, no watching that it doesn't burn, more consistent temp... Although one wouldn't get the cracklings, but I rarely end up using many of them anyway before they go bad (too rich to eat very many of them).
This is a great idea! I have done this in a way when I make pork confit or pork belly, but have not done it only for the fat output. Sous vide is a great way to do this.
There are multiple processes for rendering fat. Here are some suggestions.
The traditional method for home use is to cook chucks of fat on the stove at low temperature.
If you cook confit style sous vide (i.e. meat with some oil in a bag at 160F/71C to 180F/82C), then rendering will occur.
However if you really want to render the fat well you must grind or homogenize the fat with water first. Put the fat to render in a blender with water (nearly to cover). Blend it until it is very fine and smooth. The best fat rendering always involved grinding to very fine pieces - it dramatically increases yield. A food processor would also work.
Or you could put through a meat grinder but yield will be better if you pass through a blender or food processor after the meat grinder. This will eliminate the cracklings, but will get you much better fat yield.
Once you have the blended fat and water (a fat-shake), you need to heat it.
Here are various methods:
1. In a pan, in the oven, at 225F/110C for 8 - 12 hours.
2. In a covered pot on a set up like Pielle's PID stovetop, or a laboratory hot plate with a temperture control, or a hot plate or slow cooker with the Ranco themostat. The thermostat should be set at 180F/82C. Let it go for 8-12 hours.
3. Put the fat-shake mixture in a pressure cooker at 250C/121F (1 bar or 15 lbs pressure) for 30 min.
4. Seal the fat-shake mix in a sous vide bag and cook in a water bath or other method at 180F/82C for 12 hours. The fat can be poured off the top. If you clip the top corner off the bag, you can pour the fat off pretty well.