Recently we had really good monkfish at Librije***. According to the recipe published by Jonnie Boer, the chef, it had been cooked sous-vide at 52C/125F for 12 minutes. This surprised me a little, since Joan Roca, Modernist Cuisine and Jason Logsdon all prescribe 48C/118F. Google showed that 62C/144F is also a popular temperature in blogs. So an experiment was in order!
Here’s what I did. I picked up a nice piece of fresh monkfish fillet and cut it into 5 slices.
Each slice was salted lightly and then vacuum sealed in individual pouches labeled with the temperatures: 45C/113F, 48C/118F, 52C/125F, 57C/135F, and 62C/144F. I added 45C/113F since it was labeled in Modernist Cuisine as ‘tender’ and I added 57C/135F to have something in between 52C/125F and 62C/144, which seemed a bit of a huge step.
I then cooked each piece at the indicated temperature for 15 minutes, cooled them in ice water and refrigerated them.
When it was time to eat, I reheated all of them to 45C/113F for 15 minutes to be able to try them side-by-side.
As you can see, there was hardly any loss of juices at 45C/113F, and quite a bit at 62C/144F. We tried all of them and found that 48C/118F was indeed the best for our taste (medium rare), and that we could see why some people would prefer 62C/144F. It is drier, but still juicy and seems more tender because it is flaky.
45C/113F is OK, but on the rare side so we liked 48C/118F better. 52C/125F and 57C/135F were similar to 48C/118F but slightly drier.
We also noticed that the freshness of the monkfish (we recently tried a frozen piece and that was much drier and tougher than any of these) and the cut make a bigger difference than the temperature at which it is cooked. Monkfish has a membrane on the outside that you should cut away, but there is also some connective tissue within the fillet that is tough at all the temperatures we tried except for 62C/144F. So if you would like to serve monkfish at its prime at 48C/118F, you have to make sure to cut the monkfish such that there is no connective tissue in the cut. This also explained why the monkfish at Librije was so good, because there was no connective tissue in there whatsoever.