Rendering fat and gelatin from waste skin September 29, 2015 06:00 1 Comment
Pork belly often comes with the skin on, but you don't (usually) need the skin for bacon! Unless you want the skin for homemade pork rinds or cracklin's, it's often a waste product. Skin's loaded with collagen, though, and is a great source of gelatin. The subcutaneous fat (visible below, as Felipe of Urban Digs Farm trims a pork belly) is also a valuable resource - it's a great precursor to lard!
Usually, my first step in rendering fat is to run very cold chunks of fat through a meat grinder. The cold helps the fat grind well without mucking up the grinder. Since I just moved though, all my stuff is in storage! This chronicles an improvised method similar to what Michael Ruhlman suggests on p. 262 of Charcuterie.
I've started with the skin and fat chopped up into 1" bits in an enamelled cast iron pan. Ruhlman suggests putting only a tiny amount of water in the pot and letting it evaporate, but since I have skin and want to extract gelatin, I've added a generous amount of water to cover the pieces. I heated it to a simmer on an element and then put it in a low oven for about a day. That's about 24 hours!
The reason I left it so long is that I can see fat attached to the skin that hasn't rendered out yet. I guess the large amount of water keeps the temperature lower, making the fat slow to render out of such large pieces. The last time I did this (sorry, no pictures) I hit it with an immersion blender. This let it render quickly, but made it impossible to strain! So it ended up being a compromise.
After nearly 24 hours, I figured it was time to throw in the towel. There's obviously more fat to be rendered, but with guests on the way and a dearth of cookware, I needed to free up the pan. Here's the chunks scooped into a cheesecloth-lined colander.
The nice thing about the large chunks is that straining was a breeze! This is the fat and gelatin sans skin bits.
I funneled it all into a wide-mouth 1L mason while it was still liquid. I immediately used some of the rendered fat for tamales before taking this picture, but even so I don't think the yield was much more than a cup of lard. That's a lot of futzing for not much result, but I feel good about getting use out of the skin! It's also a good lesson for me not to cut corners and to just borrow a meat grinder (from work) next time I'm doing this.