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The Science of Green Vegetables

The Science of Green Vegetables

The age-old problem of green vegetables, often considered to be uninteresting, lies in the cooking methods used to treat them: here's how it's can be remedied.

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Let’s experiment: imagine a table set out with dishes of dwarf beans, broccoli and peas and another with rib of beef, John Dory fillets and a potato flan. Which one would you prefer to sit at? Apart from vegetarians, I think most people would prefer the second by far. And not only does this depend on the type of food being served but also on the way in which it is cooked: in fact the age-old problem of green vegetables, often considered to be uninteresting, lies in the cooking methods used to treat (or mistreat) them without any regard for their flavour, aroma and colour. How can this be remedied? Here are a few hints for cooking green vegetables in a way that does them justice and transforms them from mere side dishes to authentic protagonists of the dining table.

First and foremost, we need to know what happens to vegetables when we cook them. The keyword is obviously “heat”: in fact heat weakens the cell walls until they break down completely, releasing their content which largely consists of water, while the pectin of which the cell walls are made dissolves. This is why the cooking water tends to become sticky. These phenomena explain why vegetables such as dwarf beans become limp when cooked. Heat has other effects too, such as colour change. Green vegetables owe their colour to chlorophyll, a complex molecule containing a magnesium ion. A high temperature causes the hydrogen ions contained in the natural acids of vegetables and released during cooking to replace those of magnesium, which changes the bright colour of chlorophyll to a shade of rather dull and less appealing green. In brief, from a scientific viewpoint, cooking brings about a radical change in the vegetable. In some cases, this is what we set out to achieve but in others, we would like to cook our vegetables in a way that does not alter them excessively. So, what is the best way to go about this?

First of all, let’s get used to cooking them for a very short time, by throwing them into plenty of boiling salted water. Let this be your mantra: plenty of salted boiling water. In fact, if the pan contains a lot of water, when we add the vegetables, the temperature will not fall drastically and the liquid will regain boiling point rapidly. Furthermore, salt helps weaken the pectin structure and so makes the walls “disintegrate” sooner. In this way, the vegetables become softer in a shorter space of time. Besides, a reduced cooking time allows the hydrogen ions to replace only a minor part of the magnesium ions, which preserves the attractive colour of chlorophyll intact. It is interesting to note that, at a certain point, which varies according to a number of factors regarding the cooking method and type of vegetable, the colour of chlorophyll becomes even brighter than that of a raw ingredient. This is because the air bubbles, which are trapped in the fibres and play down the bright green colour of raw vegetables, all explode at that precise moment and reveal the true colour of chlorophyll. It is a question of a few seconds but if we learn to remove the vegetables from the heat when this happens, they will look more appealing when we serve them. Unfortunately, you have to rely on your own powers of observation, by lifting up a sample with a fork in order to assess the colour.

As soon as they are cooked, the vegetables must be drained and immediately plunged into a bowl full of icy water (filled with ice cubes to keep the temperature low). In this way, the cooking process is suspended instantly and the chlorophyll remains in optimal conditions. Furthermore, such conditions are also ideal from a nutritional point of view. It may take a little time to get used to eating crunchy dwarf beans, broccoli and peas, but at that point, it will be hard to resist the authentic flavour of a delicious dish of green vegetables.

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