Published in February 2014 issue of Prospect Magazine
I gave my mother a “sous vide” machine for her birthday because I’ve wanted to play with one for ages—Heston Blumenthal has said they “have the potential to be the biggest change in domestic kitchens since the microwave.” Until recently, these machines were cumbersome and expensive, strictly the preserve of commercial kitchens. But now you can buy smaller, cheaper versions and modernist foodies are adding them to their gadget collections. John Lewis reports almost tripling sales over the last two years.
Sous vide cooking involves compressing food in a vacuum-sealed bag (“sous vide,” “under vacuum”) and cooking it in a water bath kept at a precise temperature. Vacuum sealing requires a separate machine, so the home cook can use a Ziploc bag instead.
What happens to food when it’s cooking depends on the temperature and how long it’s in for. Meat cooks to rare at around 50°C, to rosy medium at 60°C and well done at 70°C. Non-leafy vegetables begin to soften at 85°C. But in the kitchen most methods subject food to vastly higher temperatures: water boils at 100°C, roasts tend to go into a 250°C oven and the oil in a frying pan is 200-250°C.
Consider your Thursday evening panfried sirloin: the outside is seared, but when you cut into it there is a layer of overcooked grey surrounding a pink juicy stripe of rare. This is because the sirloin has been subjected to high temperatures in order to force a bit of heat into the middle. It takes a lot of energy to transfer heat through a steak or a carrot; flesh is very good insulation. But a sous vide water bath can hold its temperature at precisely 57°C. Your steak goes in the bag in the water, and no part of it will ever overcook to grey, no matter how long it sits there.