Tuesday, December 6, 2011

A Question

Imagine you are a charcoal grill. What would you need to know about a sirloin steak in order to cook it to an internal temperature of 140°F  or 60°C?


Gary Thompson said...

That's easy. Frozen or thawed?

El Gato said...

How thick is it?

Jon in Albany said...

No perfectly shaped briquettes or lighter fluid allowed.

dave said...

In addition to the above: temperature of the coals, distance from the coals to cooking surface, shape of the grill. And 140F in the dead center, but how even do you want it? There's a lot to consider when you start breaking it down.

Bob delGrosso said...

That's exactly the point: there are lots of variables. The reason I asked is to try to find out what I'm overlooking.

Air temp, atmospheric pressure, starting temp of the meat, the rate that the heat needs to be generated, plus all the factors mentioned by you and others must be taken under consideration. It's amazing...

Natalie Sztern said...

I would need to know if my 'owner' bought a good meat thermometer so that I don't get blamed for being too hot ... wouldn't a meat thermometer be the defining tool and all else simply benign modus operandi that appears in more grilling and BBQ books than one can imagine?

Coffeemike said...

Okay, chef, let's play with this.

Heat, sound, even light - it's all energy passing through things. That energy moves at different rates depending on the substance, how easily it is transferred. Example: Air vibrates more readily than water, which vibrates more readily than rock, so sound travels faster through air than through water than through rock.

In the case of thermal transfer like this, you're talking about a temperature gradient, how hot the outside heat source is versus the center of the meat. What you're playing with, in effect, is how large that gradient is and how long you subject the meat to it.

Consider the two extremes:
* Low temperature and sous-vide cooking rely on a water bath held precisely at the finished temperature. This process runs for a long time, not only to allow thermal changes to take place (breakdown of collagen and connective tissue, for example) but also to bring the product to a very even temperature. Steak cooked in a water bath will (should) be the same temp throughout when they come out. Low gradient to start, long time, even cooking.
* On the other end is tuna steak. Super high heat (very high gradient), just long enough to sear (short time), and when you slice it you have a very thin cooked ring around an essentially raw center.

So, work with this:
- On a standard charcoal grill, uncovered, heat is basically applied from one side. The other side is exposed to ambient air, basically.
- If you want a pronounced gradient in your finished stake (say, seared crust on the outside but rare or blue on the center) then you want to hit it with very high heat. If you prefer a good crust and shoe leather, you want a gentler heat.
- Chilled vs. ambient starting temperature for the meat changes the temperature difference between the outside source and the center of the meat, so chilled meat will obviously take longer to come up to temp than room-temp meat.
- Thickness comes in here, because on a thinner cut of meat, the center is closer to the outsides so heat has less distance to travel to get to the center.
- Flipping. There's some controversy in the burger world over whether better results come from a single flip versus very frequent (every 15-20 seconds) flipping. Remember that the heat is only being applied from one side, so the other side is getting a chance to relax. Constant flipping starts to behave like a rotisserie - small bursts of high heat followed by time to relax, so you get pulses of high heat but a lower overall heat transfer.
- I said earlier (this is a tiny comment box, sorry) that this was uncovered. If you cover your Weber, then you're creating a heated environment more like an oven, with a hot source underneath. Take that into account when thinking about cooking times and finishing meat.
- Thermometers are essential, but I don't need to tell you that.
- I have some trouble thinking that atmospheric pressure or altitude will have a significant difference in grilling, but I'm very happy to be wrong. Houston is low and flat, so I don't have a lot of places to go to test this theory.

Really it boils down to: the starting temp of the meat, the finishing temp you want, and how even you want it across the piece of meat. Which, I imagine, makes recipe writing nearly impossible.

Bob delGrosso said...

Altitude/ atmospheric pressure can have a significant impact on how any food cooks via changes in the rate that water turns into vapor and rate of combustion/ oxidation of fuel. At higher altitudes water is going to leave the food faster than it does at sea level. Also, as altitude increases oxygen content of the air decreases so fires burn slower and produce "less" heat.

Make sense?