Healthy cooking techniques: steaming, oven cooking, pressure cooking and beyond the griddle

What changes in food when it is cooked?

Cooking makes food easier to digest and reduces some of its vitamins. Cooked legumes and grains are absorbed more effectively. In legumes, cooking also reduces antinutrients, substances that make it harder to absorb some minerals [4].

The greatest losses are of water-soluble vitamins, those that dissolve in water, such as vitamin C and B vitamins. They pass into the cooking liquid and are lost with it if you pour it away [4].

The opposite happens with some vegetables. After cooking, higher levels of beta-carotene or vitamin E are measured than in their raw state, depending on the vegetable [1]. That is why it is a good idea to alternate raw and cooked vegetables throughout the week.

The second variable is added fat. For cooking, preferably choose olive oil, but remember that each tablespoon adds energy. If you are trying to lose weight, the cooking method determines how much oil ends up on your plate.

The third is temperature. Above about 120 °C and with little moisture, acrylamide forms in foods rich in starch [2]. The European Food Safety Authority (EFSA) concluded that it may increase the risk of cancer. It is found mainly in fried potatoes, coffee and toasted products [2].

Steaming, boiling or poaching?

All three methods use water, and steaming results in less vitamin loss than boiling [1]. Steaming cooks food without immersing it in water and better preserves its flavour and colour. It works for almost anything, from broccoli and green beans to hake or strips of chicken.

You do not need a special appliance. All you need is a pot with a little water, a metal steamer basket and a lid. Many pressure cookers come with their own steamer basket.

Boiling still has its place. To reduce nutrient loss, use a small amount of water, add the vegetables once the water is already boiling and cut them into large pieces. Remove them when they are tender but still hold their shape. If you have vegetable stock, use it for soup or rice.

Poaching means cooking over a low heat without letting the water reach a boil, in water or stock. It is the method used for poached eggs and white fish in a little stock, which stays juicy without a drop of oil.

Oven and en papillote: dinners that need very little watching

The oven has a reputation for being slow, but it does the work while you get on with something else. A tray of diced pumpkin, onion, pepper and aubergine, with a tablespoon of oil and some spices, will last for two or three days. Meat and fish stay tender and juicy if you do not overcook them.

Roasting and baking also go above 120 °C. The same light-golden rule applies to oven-baked potatoes and bread [2].

En papillote means cooking food wrapped in a sealed parcel of baking paper. It cooks in its own steam and leaves no frying pan to wash. A salmon fillet on a bed of julienned leek and carrot, with lemon and dill, is ready in about twelve minutes at 200 °C.

If you miss the crunch of breaded food, find out how to get it in the oven in how to fry in the oven and reduce calories.

Is it healthy to cook with a pressure cooker?

Yes, and it is one of the most useful methods for eating well during the week. A pressure cooker uses little water and cooks food quickly; both help limit vitamin loss [4]. It also improves the digestibility of legumes and whole grains, which require long cooking times [4].

It is the tool that makes it easiest to cook legumes during the week. Lentils with vegetables and brown rice can be made in a single pot in less than ten minutes of cooking. Traditional stews can also be part of a healthy eating plan. What matters is the ingredients: more vegetables and legumes, and less fatty processed meat.

These are the approximate cooking times we use, counted from when the cooker reaches pressure and you turn down the heat :

• Lentils without soaking, 7 to 8 minutes
• Chickpeas or beans soaked for 12 hours, 9 to 12 minutes
• Vegetable or fish stock, 7 to 8 minutes
• Meat stock, 12 to 15 minutes
• Chicken pieces, 9 to 11 minutes
• Diced beef, 8 to 10 minutes
• Brown rice and potatoes, 7 to 8 minutes
• White rice, about 5 minutes
• Vegetables for purée, 3 to 4 minutes

Every pressure cooker is different, so if in doubt, err on the side of less time. If the food needs more cooking when you open it, finish cooking with the lid off or close it again for a few minutes. Fish should not be cooked under pressure. Prepare the stew base in the cooker and add the fish at the end, with the lid open.

Safety is simple. Fill it at least one-quarter full and never more than three-quarters full. Clean the valve and the rubber seal after each use, and replace the seal if it is stiff or cracked. Before opening, let all the steam escape.

Does the microwave destroy nutrients?

It removes less than boiling does. In a study comparing four methods for cooking vegetables, the microwave was one of the methods that preserved the most vitamin C, while boiling preserved the least [1]. This is one of the questions we hear most often in consultations, and the answer is reassuring. Microwaves cook quickly and use very little water, which helps protect vitamins.

A microwave heats the water contained in food. Once it is switched off, it does not leave radiation in the food. What you should take care with is the container. Use glass, ceramic or containers marked as microwave-safe, and cover them.

Stir halfway through so the heat is distributed evenly. A silicone steamer or a covered bowl works for vegetables, potatoes, sweet potatoes or fish in just a few minutes.

How do you stir-fry with little oil?

Use high heat, cook for a short time and keep the food moving, with a tablespoon of olive oil. That is how to make a good stir-fry. The vegetables stay crisp and keep their colour. A large frying pan or a wok helps because the food is spread out instead of cooking in its own juices.

Three combinations that work as a main dish or a filling:

• Courgette, onion, carrot and pepper with strips of chicken, for fajitas
• Cabbage, carrot and green pepper with prawns and a little brown rice.
• Pumpkin, broccoli and asparagus with cooked chickpeas

Stir-frying is quick, which is why it can sometimes end up on the menu every day. Alternating it with other methods changes the flavours and textures, and helps keep your menu varied for more weeks.

Healthy cooking means having four or five methods at your fingertips and choosing each evening the one that fits the time you have.

Air fryer or frying in olive oil?

For everyday cooking, use the air fryer; save frying in oil for now and then. An air fryer is a small oven with a fan. With a teaspoon of oil, it creates a crunch similar to deep-frying. It works for vegetable sticks, sweet potato, meatballs or fish.

It is still dry, high heat. Potatoes that come out dark from the basket contain more acrylamide, just like potatoes fried in a pan [2].

Frying in olive oil can be an occasional cooking method. If you fry food, do not let the oil start smoking and do not reuse it many times . Drain the food on absorbent paper and serve it with salad or vegetables.

How to reduce acrylamide at home

The Spanish Agency for Food Safety and Nutrition (AESAN) suggests a few simple steps, designed mainly for fried potatoes [3].

1. Store potatoes in a cool, dark place, outside the fridge [3].
2. Cut them into thick strips or cubes rather than thin slices [3]
3. Rinse them with plenty of water after cutting and dry them well [3]
4. Fry them below 175 °C [3]
5. Take them out when they are golden yellow and set aside the darker ones [3]
6. Whenever you can, boil them or cook them in the microwave instead of frying them [3]

The same colour rule applies to toast and to food cooked in the oven or air fryer [2]. Aim for a light golden colour, with no burnt areas.

What mistakes do we see in consultations?

• Thinking healthy means grilled. Grilling alone gets boring, and an eating plan that is dull is easier to give up.
• Pouring oil freely into the pan or onto the baking tray. Measure out a tablespoon and add a splash of water if the food sticks.
• Using the air fryer as an excuse to eat ready-made meals. The appliance does not change what is in the product.
• Leaving the pressure cooker at the back of the cupboard out of fear. Modern models have a double safety valve.

Almost always, the change is not about buying another appliance. It is about having two or three tried-and-tested methods for busy evenings.