Healthy Gourmet: the slow cooking revolution
A revolution is under way: the cooking rules of the past are being overthrown by a modern approach that draws on scientific insights to make food tastier and healthier.
Fear not: this does not mean that Sunday's roast will be served with the consistency of jelly or that a family reunion will feature pumpkin caviar. It is about understanding what happens to food as it cooks in order to make great meals consistently.
At the heart of this revolution is accurate temperature control. Home cooks have been relying on exotic tips and tricks in their quest to cook food perfectly. For example, using a toothpick to check if the cake is ready, or comparing the consistency of the steak with the muscle in the palm of the hand. But these solutions are approximations at best. Measuring temperature precisely is the only reliable method.
Take Thanksgiving as an example: it is often a source of frustration for the dinner host, with the turkey not turning out as succulently as hoped. The recipe calls for a given amount of cooking minutes for each kilogram; you follow the advice religiously, but it still turns out overcooked. The reason for this is that meat does not conduct heat well. The shape of food affects internal temperature more than weight, as does the percentage of water in the fibres, the amount of fat, whether or not bones are present, and so on.
The solution is simple: use a digital thermometer to control the core temperature. At 55 degrees Celsius, a steak is medium rare, at 65 degrees it's medium, and at 70 degrees it's well done. Always.
The same approach applies to fish: they are best when the cooking time is short. Heating denatures the proteins of fish, distorting the nutrients and drying the tissues. This process starts at 45 degrees Celsius, but is drastic at 60 degrees. Do not let the core temperature of a tuna fillet exceed 50 degrees.
The secret of many tasty foods is scientifically called the Maillard reaction. The molecules that trigger the sense of flavours that make food tasty are generated by the reaction of amino acids with sugars. This happens only at certain temperatures, notably between 140 and 180 degrees Celsius.
The traditional cook will make a steak on a pan which is not hot enough or will overcrowd the pan. These errors will prevent the surface of the steak reaching the 140 degrees Celsius needed for the Maillard reaction. The cook will end up with a piece of meat that is dry - because the proteins will coagulate, letting out the juices - and hard, because the fibres will contract.
The modern cook, aided by a digital thermometer, will cook the steak briefly and at a high temperature. He will not turn the steak immediately, for fear it will attach to the pan, but will wait no more than two minutes, until the reaction occurs and the steak detaches itself from the pan.
Taking care to control temperature is also a matter of healthiness, not just taste. Beyond 180 degrees Celsius, toxic molecules form on the surface of the steak.
A pressure cooker is another valuable piece of equipment, particularly to prepare tasty and healthy stocks and sauces. When these are being boiled, because they are full of water, they do not reach the temperature necessary to generate the chemical reactions needed to create flavours. To make stocks and sauces tasty, the tendency is to cook them until they are dried out: of water and of nutrients. A pressure cooker avoids this problem, as the temperature inside is significantly higher than that of a boiling pot. Look for pressure cookers of the new generation; they have a spring valve that keeps the aromas inside.
Sous-vide equipment is the crown jewel of the modern cook at home: ingredients are vacuum packed and immersed in a water bath, where they remain until the food is at the same temperature as the surrounding water. The water is maintained at the target temperature, within a range of a single degree Celsius, by a computer-controlled heater. This process allows for results which are difficult to achieve by traditional means, allowing uniformity of temperature throughout the food.
Another advantage is that it does not matter how long the food stays in the water, it cannot overcook. This frees the cook at home from one of the most difficult things to master in the kitchen: timing. Longer cooking time allows for textures in food never dreamt of before: try cooking beef ribs at 58 degrees Celsius for 72 hours for mouth-watering results.
Cooking at controlled low temperatures can be done without a computer-controlled heater, albeit the process is more laborious. This week's recipe shows how to cook an egg at 65 degrees Celsius for one hour - the signature dish in many Michelin-starred restaurants. Just a pot and a thermometer are needed.
Eggs cooked at home often come out with a gummy white and a dry yolk. The tendency to overcook them is because the yolk takes longer to cook than the white. The final consistency of an egg is determined by the coagulation of its proteins. At 65 degrees Celsius, only one of the proteins of the egg white coagulates, leaving an incredible smooth texture. At this temperature, the yolk is cooked as well and has a gratifying creamy consistency.
Four litres of water
- Put the water in a pot over the smallest burner and cook until the water reaches 70 degrees Celsius, using a digital thermometer to check.
- Switch off the heat and put a lid on the pot.
- Wait until the temperature of the water drops to 65 degrees.
- Delicately place the two eggs in the water, taking care to keep them separated.
- When the thermometer reaches 64.5 degrees, cook on minimum, until the temperature goes back to 65 degrees - it will take about a minute.
- Turn off the heat again, until the temperature drops to 64.5 degrees (about 10 minutes).
- Repeat the process for one hour.
Andrea Oschetti is a private chef. cuoreprivatechef.com