Dinner last night had something for everyone: Jessica got a bloody-rare steak, Erwin got creme brulee, and I got to use a blowtorch… and Fourier series. It was a good night for all of us.
One of my new favorite blogs is Kamikaze Cookery , a delightful UK food blog that mixes food-geek bloggery with hilarious videos of food experimentation interspersed with somethingawful-esque cartoons. I highly recommend it. In their first such video, they did a DIY (i.e. not made with $1000 worth of equipment) steak sous-vide, and I was inspired to try it myself.
What the hell is sous-vide? It’s actually a really simple idea. When you cook something, say a steak, there is an ideal temperature that you would like the steak to reach before you eat it. Depending on how you like the steak, this can range from 120°F (rare) to 160°F (well done). Typically when you cook a steak, you apply heat much greater than the target temperature to the outside, and keep doing this until the center reaches the target temperature. Along the way, of course, the outside reaches much higher temperatures, and you end up with a steak with an inhomogeneous temperature distribution. This means that a significant portion of your steak is, in fact, overcooked. Sous-vide gets around this problem by using a water bath to only apply heat at the level of the target temperature. No one wants boiled steak, so the meat is sealed in a vacuum bag with flavoring agents before being put into the water.
Since the applied temperature is so low, the cooking time is quite long, on the order of an hour for a standard size cut of beef. The cool thing, though, is that you can’t overcook the meat since the ambient temperature in the bath is the target temperature. This means you can actually leave the meat in for much longer; this continues to break down the tough connective tissues while preserving the ideal doneness. The result is an amazingly tender steak, cooked to perfection.
All of this got me thinking about heat transfer. As some of you may know, I’m a bit of a math fancier. As such, I did what any respectable math enthusiast would do in this situation: I built a mathematical model using the heat equation with Newton’s law of heat transfer for an inhomogeneous Robin boundary condition. This gave me a nice partial differential equation whose solution would tell me how the temperature in the steak evolved as a function of both space and time. To solve the resulting partial differential equation, I used an expansion into eigenfunctions of the Laplacian with matching Robin boundary conditions, which is effectively a Fourier series expansion. These boundary conditions muck up the analytic calculation of the eigenvalues, so I had to attack the problem numerically with my favorite math computer program, Maple. After screwing around for the better part of an afternoon, I cooked up a pair animations that show the evolution of the temperature in the center cross-section of a 10×5x1 steak. In both cases I assumed that the steak started off at 45°F. For the first animation I considered the sous-vide cooking method in a 135°F water bath.
For the second I considered grill cooking with an external temperature of 500°F.
Note that in the second animation, the cooking is not actually happening more slowly than in the first. I had to artificially slow down the animation in order to be able to see what was happening. You can see the difference in the two cooking methods quite distinctly. Sous-vide brings the temperature up to the target nearly uniformly, whereas grilling has a decent portion of the steak hundreds of degrees overcooked when the center hits the target temperature. Isn’t math glorious?
Oh, right. I did some cooking, too…
I didn’t have a vacuum sealer, so I used zip-bags and a straw. It basically worked. My flavoring agents were s+p plus a little butter for good measure.
Into the pot, which was held around 130°F, the ideal temperature for medium-rare.
It’s important to keep the temperature equalized, so you have to constantly monitor the water with a digital thermometer. I was able to stay locked at 134°F for most of the cooking time. This is about 45 minutes in. You can see that the steaks have started to change color.
To put 134°F in context, I put my hands directly into the water.
And here we are at the end of cooking time, an hour and a half later.
The sous-vide can only take us so far, though. Part of the delight of meat cooked at high temperatures is the delicious browning and caramelization that results on the outside surface (cf. the Maillard reaction ). Sous-vide gets you none of this, so you have to add it at the end. With a blowtorch!
Chef.
Gangster.
Process.
FAIL! My little torch just wasn’t powerful enough to get the browning right. I had to go to Plan B: fire the steaks briefly in a super-hot pan. This is how it turned out. I made some sauteed Brussels sprouts for the side, btw.
Jessica approved. Check out the color inside that thing. It’s all pink! (Unless I’m mistaken, that phrase was once uttered by a human female.)
The result? Holy shitballs was that a tender steak!!! As I’ve mentioned before, I’m not the biggest fan of a hunk of meat without lots of flavoring, but this was pretty spectacular. It was probably the most tender piece of steak I’ve ever had, and even thought it was somewhat lacking the Maillard brownness (I’ll use a grill to finish next time), the fact that it was perfectly medium rare throughout more than made up. Also, and I can’t stress this enough, the process itself was insanely easy. You should absolutely try it yourself if you dig on the cow-slab.
<jessica> And as someone who does indeed dig on such a slab: I agree, that was a tender steak. I did, though, have two small problems with it. First, see that great big stripe of fat that goes through those ribeyes in that first picture up there? Well, it didn’t melt. If you put that on a grill, it’ll melt into the meat and make everything else all extra-yummy, and any parts that don’t melt will get all super-black and argle garg garg…oh, sorry, drifted off there for a second. Well, this still kind of tasted the way it was supposed to (yeah, that’s right, I ate the giant hunk of fat. you think you’re better than me???) …but it was also just a big weird stripe of fat. And the only way to solve this problem is to bring the water up to a temperature high enough to melt it, which is too high a temperature to keep the steak itself really rare. (ALSO! I only just now this second learned that Ian had purposely cooked them to be “medium-rare!” I’m positive that he told me at the time that he was going to make them rare! He’s a cheater!) The second problem was what Ian already mentioned (though he used some smartypants frenchiefrench word for it): it didn’t get black enough on the outside. Throwing it in the pan worked, I guess, but it also was enough heat or time or whatever to take away some of the steak’s original rareness. I do hope these two problems can be overcome, though, because it was pink as fuck and wacky-tender and anything that’ll make Ian make me steak is something I’m all for.
Also, Ian made creme brulee! Everyone likes creme brulee! Especially Erwin, it turns out. Our cat is a gourmand! Or at least a pig. </jessica>
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