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Thursday, March 31, 2011

BBQ and Low Temperature Cooking

This blog actually started out somewhere else that I was going to go, but it took on a life of its own, so I just started following it. I hope to get to the direction I was heading in a future post!

If you've been reading this blog from the start, then you will be aware that I have been cooking BBQ for a long time - I started trying (!) in 1986. It was hard back then because we were living in Florida, there wasn't any BBQ insight available that would lend insight on how to make it, and there wasn't any Internet (although I did have a usenet feed via uucp to a UNIX system I was running at home - circa 1989).

BBQ, for the uninitiated, is cooking tough cuts of meat, at a low temperature, for a long period of time. Since, as all God's chosen (Southerners) know, BBQ is only pork - it ain't beef, and typical cuts are the shoulder , which when split yields the Picnic and the Boston Butt.

Butt butt butt you say, I thought the butt was at the rear end of the pig! Nope; it's at the shoulder/neck, where the shoulder butts up against the neck. The rear end is the Ham, and that's a whole different creature.

While you will see references as high as 250dF to cook BBQ, this is a poor way to make it. People that smoke their Pork at 250dF are doing it because they are in a hurry, and don't mind sacrificing quality for speed. Well, go to McDonald's and get a McRib. You'll also see references to 225dF, which is better, but no joy yet. Real BBQ has to be done below 212 (at sea level; lower if you live higher).

Think about this: I'm sure you've seen a pressure cooker in action. That pressure is created by boiling water, and water boils (at sea level, lower temperatures at higher elevations) at 212 dF. You've got to put a lid on that pot and lock it down to be able to contain that pressure - it's trying to burst out!

So what's going to happen to meat that you cook above 212 dF? It's going to heat the water in all the little cells, cause them to expand, burst through the cell walls, and flow out of the meat where it will evaporate. You just lost a lot of moisture.

But flavor is transported by fat; so what happens to the fat when you cook at 250dF? Pork fat [rules]starts to render out of the meat at 140 dF. The higher the temperature, the faster it renders. So if you are looking for low-fat BBQ, then continue to cook at 250 dF, or 225 dF.....and you are tossing a lot of that flavor out of the meat.

So why are people cooking at 250 dF and at 225 dF? It's because they are in a hurry. Well, I'm cooking BBQ for FLAVOR and I'm not in a hurry to get it!

Note that we are concerned with two different temperatures here. The first temperature we are concerned with is the temperature of the oven, while the second temperature is the internal temperature of the meat. The temperature of the oven determines, ultimately, the highest internal temperature the meat will reach. For instance, if I cook at an oven temperature of 145 dF, then the internal temperature of the meat can not ever go above 145 dF, regardless of how long we leave the meat in the oven....2 years later and it will still not be above 145 dF.

So the oven temperature determines the following things: it determines how fast the internal temperature of the meat will come to your desired temperature; it determines what the maximum internal temperature of the meat can reach; it determines the temperature difference between the outside meat and the inside meat; and, since temperature determines the amount of time you can leave the meat in the oven, it also determines the tenderness of the meat.

The higher the temperature of your oven, the faster heat will be transferred to your meat. It can only be transferred by going from the outside of the meat into the inside of the meat. So the outside of the meat is going to get hotter and this hotter temperature will gradually be transferred into the interior of the meat. The higher the outside temperature of the meat, the higher the difference between the interior of the meat, and the faster the transfer. If the meat is left in the oven long enough, then at some point, the interior temperature and exterior temperature of the meat will reach equilibrium, and no further transfer will take place; the whole of the meat is at a steady uniform state.

When people look at cooking temperature vs. time charts, for example when cooking a Thanksgiving Turkey, they are interested in two things: the oven temperature, and the time to leave the turkey in the oven at that temperature. That temperature and time solution is solving the following problem: trying to cook the turkey in the shortest time, while getting the interior of the turkey done. Too long at too high a temperature and the surface is dry and hard while the interior is just right. Too short at too high a temperature and the surface is just right while the interior is still raw. So the temperature that is chosen is that which will satisfy the need to have the surface not too dry while the interior has had enough time for the heat to migrate into the interior and bring it up to a safe, good temperature.

The larger the piece of meat, the greater the distance from the surface to the interior middle of the meat. The larger this distance is, the further the heat has to travel, and the longer it takes for the heat to do so. So big pieces of meat takes longer for the heat to migrate into the interior - another way of saying this is it takes longer for the meat to get done.

This is the reason fast food hamburgers are wide and thin - the heat migrates all the way through in just a few minutes; the whole thing is done, at the same temperature, in a really short amount of time, so you can blast it with a lot of heat. Thicker pieces and you've got to lower that temperature and cook it for a longer time to allow the heat to migrate to the center.

Harold McGee, in "On Food and Cooking" remarked that the real way to cook something would be to cook it at the desired temperature you want it to end up at. In other words, if you want your BBQ to end up at 160 dF, which the US Government says is safe, then you want to cook it at 160 dF. However, Alton Brown says that pork is at it's prime at 145 dF.

That means I may want to cook mine to 145 dF, as that is probably the best temperature for flavor. But I haven't tried this yet, because I haven't had an accurate enough low temperature oven and temperature controller yet....but I'm changing that! I have cooked a Chuck Roast at 165 in a low temperature oven. It came out tender and moist.

Pork cooked to 145 or even 160 won't look very appetizing; it will look gray - dull, and unappetizing. To improve that, you'll want to place that Pork into an oven (a smoker is an oven, just with some smoke in it) at 325 - 400 dF after cooking at 145 or 160, in order to create a Maillard Browning effect. But at 325 - 400 dF for how long? I'm not sure yet, but I'm researching; so in the meantime, you'll have to just put 'er in and watch till it gets to the point where it looks like you want it to look!

But back to how long to cook the Pork meat at 145 or 160 dF?

That brings us to Low Temperature Cooking.

Sous Vide has pioneered low temperature cooking for the average cook. However, we've already seen that BBQ is the basis for low temperature cooking, and Sous Vide is just adapting this approach, by putting it into a plastic bag, removing the air, and cooking it low and slow.

If you read about Sous Vide cooking, you will note one similarity with this approach and BBQ - how tender the meat is.

So, if our goal is to cook BBQ and have it at it's peak (which for me is 145 dF), and at it's NC style Pulled-Pork tender, then you need to cook it for at least 2 days, and maybe 3 days...I don't know yet, but I'm going to experiment to find out, and when I do I'll post an update here.

Which leads me to the post I actually wanted to make - low temperature cooking, which will be in a future post.

I'm designing and building a low temperature controller for a low temperature cooking oven.

When I've got it completed, I will post it here.

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