Cooking food makes it more digestible and makes chewing easier ( 1 ). Raw, certain foods have anti-nutritional factors that cooking will destroy. For example, explains Dr. Juliette Pouyat in the guide The Right Choice for Cooking, “The starch of pasta or rice becomes digestible after cooking in water thanks to a modification of its structure more favorable to the action of the amylase which breaks starch into glucose molecules. The temperature will also denature proteins, open their folded structure, and facilitate the action of digestive enzymes.

We also cook food to make it edible, destroy harmful microorganisms, and preserve it better. Cooking also makes it possible to obtain pleasant aromas that come from chemical reactions grouped under the name of Maillard reaction. But this reaction is double-edged: it leads to flavors that are highly appreciated by the consumer but the molecules involved are suspected of promoting the development of certain cancers or inflammatory reactions.

Cooking can, however, lead to a deterioration in the nutritional quality of the food, with a loss of vitamins, denatured by heat, and the appearance of undesirable compounds. For healthy cooking, the benefits of steam cooking are often praised.

What is the point of steaming?

With gentle steam cooking, the temperature does not exceed 100°C and the initial taste of the food is preserved. “It has the advantage of minimizing loss by diffusion of vitamins and minerals and makes it possible to create a humid environment which does not favor the formation of Maillard compounds,” explains Juliette Pouyat. This cooking method avoids the use of fat, which allows for healthy cooking.”

Cooking vs. Microwaving and Other High-temperature Cooking

The benefits of steaming were demonstrated in an experiment carried out at Zhejiang University in Hangzhou (China) where scientists compared five common cooking methods for broccoli ( 2 ): steaming, microwave, boiling, stir-frying alone, and stir-frying followed by boiling.

The results showed that all cooking treatments except steaming resulted in significant losses of chlorophyll and vitamin C and decreases in total soluble protein and soluble sugars. Glucosinolates, beneficial molecules found in cabbages like broccoli, were significantly altered by all cooking treatments except steaming.

Practical questions in the kitchen

Potatoes, broccoli, asparagus, carrots… What foods for steam cooking?

Almost all foods can be cooked with gentle steam: vegetables, meats, fish, cereals (wheat, barley, quinoa), legumes (flageolets, chickpeas, beans, lentils, etc.), fruits.

Pressure cooker, casserole dish… Which steam cooking device?

Gentle steam cooking can be done with electric steam cookers, stainless steel pots with holed baskets, or with the Marion Vitaliseur. But a saucepan and a suitable lid can also do the trick (see below).

To steam food under pressure, you need a pressure cooker. There is a wide variety of pressure cookers of this type, some offer programs that adapt to the type of food to be cooked. In these devices, food is steamed at a pressure higher than atmospheric pressure and at a temperature not exceeding 100°C. “Certainly, this high temperature is unfavorable for the preservation of vitamins but the cooking time is shorter, points out Juliette Pouyat. In addition, certain pressure cooker models (the Nutricook from SeB for example) are capable of evacuating 90% of the air in the utensil, which helps avoid too much exposure of the food to the oxygen in the air.” However, oxygen is the cause of undesirable reactions: degradation of certain vitamins and lipid peroxidation. By reacting with oxygen in the air, antioxidant substances (vitamin C, vitamin E, polyphenols, etc.) and polyunsaturated fatty acids lose their nutritional value. These reactions can also generate highly reactive compounds that will attack other molecules.

How to steam when you don’t have a steamer?

You can use a large saucepan. Pour about 2 cm of water into the bottom of the pan and bring to a boil. Place the food and close it with a glass lid, preferably with a small hole so that steam can escape. Otherwise, open the lid from time to time.

There are also steam ovens equipped with a special compartment for putting water. The oven uses the heat generated to cook the food.

How long does it take to steam?

The steam cooking time varies and depends on the type of food cooked but also on their size and the desired cooking (crunchy or tender vegetables). “ The cooking time for cereals and legumes also varies depending on the soaking which precedes cooking,” explains Juliette Pouyat.

Cooking: 1 hour

Ingredients for 4 persons

• 4 steaks or tuna steaks
• 1 small bowl of fresh-shelled coconut beans
• 3 zucchini
• 3 spring onions
• 300 g hulled green beans
• 1 bunch of basil
• 1 clove of garlic
• 5 cl of olive oil
• Gray sea salt or herbal salt

Preparation

Pour 15 cm of water into the Vitaliseur pot, cover, and bring to a boil. Pour the coconut beans into the steam basket and place them over boiling water, cover, and cook for 50 minutes.

Meanwhile, wash the vegetables, basil, and garlic. Cut the zucchini, spring onions, and beans into equal-sized pieces, i.e. 1cm cubes.

Prepare the pesto: mix the chopped basil, garlic, oil, and a little salt for 20 seconds. Remove the herbs stuck to the sides and mix again.

When the 50 minutes are up, taste the beans and adjust the cooking time. When they are to your liking, add the green beans, cover, and cook for 4 minutes, then add the zucchini and spring onions and cook for 3-4 minutes.

Remove the cooking basket and pour all the vegetables into the soup bowl with the pesto, mix, and cover to retain the heat.

Place the tuna steaks in the steam basket, cover, and cook for between 2 and 4 minutes depending on the desired doneness.

How to steam vegetables?

For steam cooking in a pressure cooker: fill the bottom of the casserole dish with a little water, place the vegetables, and close the casserole dish. Cook over low heat until the valve whistles. Calculate the cooking time depending on the food prepared (around 10 minutes for green beans for example).

For steaming in a steamer: follow the manufacturer’s instructions. Generally, you have to fill a water tank and place the food in the different cooking compartments. Cooking time depends on the food.

In conclusion

The advantage of steam cooking is that it preserves vitamins and minerals that could be lost in other cooking methods. With gentle steam, the low temperature limits the production of toxic molecules.