If you’ve tried sous vide for yourself, you’ll know that it produces incredible, restaurant-quality results, but have you ever wondered exactly how it works?
Sous vide cooking itself is as simple as vacuum sealing your ingredients, selecting a cooking temperature and time and leaving them to cook, but there’s actually a lot of science going on behind the scenes.
The Problems with Traditional Methods
What it ultimately comes down to is the fact that water is a much more effective way to transfer heat to food than via air (in an oven) or a hot piece of metal (in the case of a pan).
The goal in cooking is usually to bring the food which you’re cooking to a specific temperature, at which it is considered to be perfectly cooked.
This means that if you’re using these more traditional methods of cooking, you’ll need to set the temperature a lot higher than the desired temperature of the food to reach this point.
However, with lots of foods, such as fish and steak, the margin for error is very small which opens up the risk of overcooking or burning the food if you’re not careful.
As an example, let’s say you’re cooking a steak on the grill which you want to be medium rare (an internal temperature of about 56˚C) with the grill set to about 210˚C.
This means that the outside of the steak will be well done well before the core reaches the desired doneness, forming a large temperature gradient between the surface and the core, even though you’re only grilling for a short space of time.
Alternatively, if you’re cooking in a pan, the surface of the pan could be about 30 degrees hotter than the centre, and if you leave the steak for just a little bit too long at these extremely high temperatures, it’ll be overdone and tough.
The Sous Vide Solution
However, this is where sous vide comes in. Because water transfers the heat a lot more efficiently, the food is cooked a lot more gently, and held at exactly the right serving temperature without exceeding it.
So for the example of our medium rare steak, it’ll simply be held at 56˚C (with an accuracy of as much as 0.1˚C) until it’s evenly cooked throughout, without ever overcooking, meaning you don’t have to worry about timing.
Holding the food at an exact temperature might make more of a difference than you’d think, because just a couple of degrees either way can make a big difference.
The importance of temperature control is best illustrated with eggs, with which the proteins break down at between 54˚C and 71˚C.
That’s quite a big range, and obviously, the eggs are going to cook a lot quicker the higher the temperature.
So, for example, if you cooked eggs sous vide at the lower of this range, you’ll get a loose white (runny and clear).
However, with just a few more degrees, the whites will start to solidify, but the yolk will remain runny.
A few degrees more and you’ll get something closer to a hard-boiled egg, so you can see just how important the accurate control that sous vide gives you is.
(Check out our Guide to a Perfect Egg to see exactly how to get your eggs just how you like them!)
Something you’ll also notice with sous vide is that it gives you a very tender meat. This is because it effectively breaks down the collagens and proteins which make food tough and chewy, but preserves the muscle and other important parts which provide texture and taste.
Vacuum packing is also an important aspect of sous vide cooking. This process is crucial because it stops air from insulating the food and slows the rate of oxidation, which can lead to unwanted colour changes and strange tastes.
It’s also important for locking all of the nutrients and other good stuff into the food, as these would be leached out into the water if they weren’t securely vacuum sealed.
This is especially good when cooking steak, as all the juices are retained and could even be kept and used in a sauce if you wished.
Now that you’ve got a slightly better understanding of exactly how sous vide works, what are you waiting for?
Check out our full range of home sous vide machines here and see the results for yourself!