Thursday, May 6, 2010
Okay, maybe that's not exactly it, but it sure seems that way. According to Wikipedia, sous-vide means "under vacuum" and it's a method of cooking foods for a long time at controlled low temperatures with the food vacuum-sealed in a plastic bag. And the bag of food is usually in a waterbath, which keeps the temperature stable and constant.
The plastic bag technology is easy. I've got a vacuum sealer, but a zipper plastic bag with the air squeezed out is also an option. The controlled low temperature is usually the sticking point for people. The immersion circulators that the pros use are big and expensive, but the water temperature is tightly controlled, and the water is constantly moving so there are no hot spots.
Recently, there have been a number of posts on Serious Eats about differenet methods for creating a sous-vide environment, including one article about doing the cooking in a beer cooler. Since the cooler is insulated, it keeps the heat in long enough for food to finish cooking before the water temperature drops significantly. For longer cooking you can add hot water as needed to keep the temperature up.
One problem often cited with the home sous-vide method is that if the temperature isn't monitored - or at least checked once in a while - the temperature could fall below the safe temperatures and into the range where bacteria are growing instead of being killed.
Most bacteria stops multiplying at 125 degrees and starts dying off at 130 degrees, so you don't need to get chicken up to 160 or 165 degrees for it to be safe. The thing is, the bacteria is killed immediately at those higher temperatures, but down around 135 degrees, it might take an hour and a half to kill all the little monsters.
The idea is that with sous-vide, you can cook a piece of chicken to 140 degrees and keep it exactly at that temperature for as long as you want it there. If the chicken remains at that temperature for 35 minutes, it's perfectly safe. If it stays at that temperature for another hour, it's not overcooked because it never goes above the 140 degree mark. Which is another great thing. You can have the food fully cooked and sitting at the perfect temperature for hours with no loss of quality.
When we're talking about cooking to 140 degrees for 35 minutes, that doesn't mean it sits in a 140 degree bath for 35 minutes. First the interior of the chicken has to reach that temperature, and then it has to stay there for the 35 minutes. Which is why you want the water to stay at that target temperature for a relatively long period of time, which in turn gets the entire piece of chicken to that temperature and keeps it there.
What sous vide doesn't do is brown the outside of the meat. But that's easy enough to fix with a little stovetop searing after the meat is fully cooked.
In reading through the posts at Serious Eats, I had a sudden bright idea. If the meat was in a waterbath in a pot and the pot was in a warm environment, preferably the same temp as the cooking liquid, the pot wouldn't lose heat to the environment. If the environmental temperature could be controlled, then it should be possible to sous-vide cook something for an indefinite amount of time without the need to fuss with adding hot water to a cooler.
It made perfect sense, and I had an environment that could be controlled - my oven. Since my oven has low temperature settings for warming and food drying, it seemed perfect. The odd thing was that although my oven walls and the internal temperature of the oven were both reading the set temperature, the pot still seemed to be losing heat. I don't know if it was the cool food in the warm water that was sucking the heat, or if it was my choice of pot, but I needed to increase the oven temperature a bit to get the water temperature to stay stable at the correct temperature. But once I got everything stabilized, the water temperature, monitored with a remote probe thermometer, didn't budge at all.
For my first experiment, I used a Corning glass dutch oven. Next time, I'll try a cast iron dutch oven and see if that makes any difference in terms of heat retention or transfer or whatever's going on in there.
As far as the meal, I cooked three chicken breasts, with bone and skin. They were cooked perfectly, although there was some pinkness right next to the bone. The meat wasn't undercooked, and I've seen that same pinkness on overcooked meat that's next to a bone. For presentation sake, I think next time I'll bone the breasts before I cook.
This time, I didn't season the meat at all before cooking. I wanted to see what the method would produce. After, I seasoned them and browned them a bit with olive oil.
Next up, I'll have to try some steaks or chops, and in the future I might try something that cooks for a long time, to see if I can keep the temperature stable for the longer periods of time that it takes to cook tougher pieces of meat. According to what I've seen, that might be in the range of 48 hours. I think that the hard part might be going without baking anything in that oven for that period of time. But I think I can work around it.