Osmosis, discover what it is

Today we will talk about osmosis. What it is, what uses it has in haute cuisine and how we apply it at Agust Barcelona in our Japanese whisky marinated duck foie gras terrine with osmosed pear.

It has often happened to us that, when we go to a haute cuisine restaurant, we are unfamiliar with some of the more technical terms that appear on the menu, so we end up asking the staff for help or we choose another of the dishes available in the menu.


From a scientific point of view, it is the diffusion that takes place between two liquids or gases capable of mixing through a septum or a semi-permeable membrane. In this way, a balanced solution is obtained.

In an easy way, osmosis is the opposite of dehydration. By this technique, liquid is added to a product thanks to its permeability. The aim is to have a rehydrated product containing the characteristics of the liquid it has been mixed with.


Now that we know what osmosis is, let’s see how it relates to gastronomy.

This scientific technique is increasingly used in avant-garde cuisine to improve chefs’ recipes. Although it may seem a very elaborate technique, it is actually easy to use and, above all, very tasty, as it changes and gives new flavours and textures to the different products.

Let’s take a look at some practical examples:

Firstly, when cooking fish, meat or other food with water, if we do not add salt to the food before cooking, the natural salts and aromatic substances in the food will pass into the water in order to balance the inside and outside salt concentration. The result will be a very rich broth but a blander food, as all the elements will have been balanced.

On the other hand, if you add salt to the food before cooking, the mineral salts and aromatic substances will not pass into the broth, because the balance between the inside and the outside of the food will have already been achieved.

A final example would be when dry-pairing fish, such as salmon, where we add salt to the product in order to extract its water, completely changing its texture, colour and flavour. As a result, we prolong the shelf life of the product.


At Agust Barcelona we use osmosis to prepare our osmosed pear, the foie gras accompaniment.

To prepare the accompaniment of this delicious dish, we take the pear and peel it. We cut these ingredients into wedges and dip them in syrup. The syrup is prepared by mixing equal parts water and sugar.

At this syrup we are going to add a little cinnamon, aniseed and lemon and orange zest. We are going to boil all this with some Japanese whisky. Sounds delicious, doesn’t it?

We’re going to boil the ingredients for about three or four minutes to take the hardness out of the pear. Once done, we are going to set the pear segments aside and let them cool in the fridge.

In order for osmosis to take place, the pear must have been boiled. This makes it easier for it to absorb the liquid from the syrup sauce.

And that’s it!

Now the osmosed pear is ready to be diced and served with the foie gras. Now the accompaniment has a sweet taste with a touch of aniseed, but without alcohol, as we have evaporated it.

As a final result we have a dish with a wonderful and stupendous taste in the mouth.


We are waiting for you in our restaurant to enjoy an authentic and delicious gastronomic experience, not to be missed!