Salmon Sous Vide

Finally, with the hacked mini-fridge turned temperature-regulated sous-vide cooker, it’s time to cook some salmon!

DISCLAIMER: I’m an engineer, not a chef! There are plenty of really good sous-vide recipe sites out there, if you try these, there are no guarantees of edibility whatsoever.

Tools and materials used: 1x hacked mini-fridge, 1x salmon fillet, seasoning for the salmon (in my case, salt, pepper, beer that nobody wanted, light soy sauce, parsley, dill).

Seasoning the salmon.  I am using the same seasoning for the salmon as my microwave salmon recipe:  dash of salt and pepper, and then slather with light soy sauce and beer (normally I would use an asian beer – Tiger or Tsingtao, but here I’ve used a bottle of Becks that has been lying around for a while now that nobody’s been willing to drink), and some herbs (parsley and dill).

Sealing it up:  Normally with sous-vide cooking, the food is vacuum packed (“sous-vide” means “under vacuum”), I didn’t have a vacuum sealer or vacuum bags, so I’m using the next best thing – food bags.  These are Tesco food bags, and I’m specifically using these because they’re microwave safe (I take that to mean it’s not going to leach any nasty chemicals at high temperatures).

To “vacuum” seal these  bags, I can simply immerse it in water.  The water squeezes all the air out of a bag.  The result is almost as good as a vacuum packer, and plenty good enough for sous-vide use.

Next I set the mini-fridge to 50°C via USB with my control app (thos following the build may remember that I neglected to actually install any buttons on the outside of the fridge, and so all the controlling is done over USB).  The PID controller gains are set to P=60, I=0.1, D=0, values that gave us good results when I was doing the PID tuning previously.  Again, if anyone wants my code, contact me!

In it goes.  The salmon is kept off the bottom with a simple plastic construction (made from the mutilated halves of the plastic shelf which came with the fridge).  Next time I’ll add a bit more water.

One thing I had been concerned about was the possibility that the temperature inside the fridge would drop by a large amount when the cold food went in.  The data log does register this drop, but the effect was not too bad.  It’s possible to quite clearly see the rapid drop from 50°C to 48.5°C as the salmon was inserted (the two sharp drops correspond to the heat loss when the fridge door was opened, first to insert the plastic frame, and the second time to insert the fish).

The temperature recovers slowly (since the fridge’s peltier element is only capable of producing about 70W of heat at those temperatures), however because of this slow rise, the integral component of the PID controller has time to wind up, resulting in a large overshoot as the integral unwinds.  I should be able to reduce the effects of this by adjusting the PI gains next time, however the easiest thing for us to do is to raise the temperature to a couple of degrees higher than before putting the food in.

After 40 minutes, the salmon is medium done, the way I like it.  People who like their salmon rare, or well-done, would set the cook temperature higher or lower by a few degrees.

I also like my salmon to have a bit of crispiness, so it goes onto my cast iron grill skillet briefly for some Maillard reactions (I can’t emphasise how awesome this grill-skillet is, it can turn regular bacon into EPICBACON).

Unfortunately the salmon fell apart a little bit on the skillet, and it looked so good that I started eating it before I could take this next photo, but this is truly incredible salmon – underneath the crispy and aromatic outer layer is an incredibly tasty centre with the perfect amount of juiciness and tenderness, a gentle suffusion of seasoning, and a texture far more consistent than can be achieved through other means of cooking.

This photo doesn’t do justice to the tastiness of this salmon, I will have to add some pictures when I next cook some salmon.


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