04 October 2013
So, if you haven't already heard of Sous Vide cooking I'd highly recommend reading a bit about it. In a nutshell, it is cooking food in a water bath at a certain temperature with the idea being that the food cooks slowly and evenly resulting in a perfect steak, or whatever it is you are cooking.
With a steak for example, you will usually have a temperature gradient across the meat resulting in a pink centre and increasingly darker and cooked meat towards the edge. With sous vide cooking, the steak is cooked exactly to your specifications throughout the meat evenly. You then finish off the crust of the steak quickly with a blowtorch or in a pan.
However, sous vide cookers for domestic use are very expensive indeed. But, with a bit of time and not a great deal of effort you can make your own for a fraction of the price. Many people hack slow cookers, crock pots or rice cookers into DIY Sous Vide cookers. I happen to own a slow cooker that rarely gets used so I thought I would see if I could repurpose it into a Sous Vide cooker to make the perfect steaks.
So the first thing to do was to find out if the slow cooker could reach the temperatures necessary for cooking sous vide style. Typically you want temperatures ranging between 50-60°C for the perfect steak and up to 80° for other items. So I had a DS18B20 temperature probe lying around so I hooked it up to an Arduino and set it to take a temperature reading every 5 minutes and print that to the serial monitor. That way I could see over time how long it took to get to temperature and if it could reach at least the temperatures necessary for a perfect steak.
Over the next 2 hours the cold water I put into the pot was heated slowly up to around 65°C so I knew it would be ideal for how I like my steak (rare). I decided to leave it on overnight and see just how hot it got. The next morning the temperature was just over 97°C, which was a surprise.
So, I now know that the cooker can be used to cook meat sous vide. All I need to do next is to create a control unit that keeps the water bath at the exact temperature necessary. I will work on that at some point in the not too distant future and will give you all an update.