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The Science of Agar Agar

The Science of Agar Agar

A closer look at agar agar, a carbohydrate-based substance derived from certain species of algae with a high jellifying capacity.

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In cooking, the conversion of a liquid to a solid is looked on as being more of an X-Man type power rather than a culinary skill. In actual fact, the only example we are really familiar with is that of freezing temperatures used to turn water, broth or fruit juice into ready-to-use ice cubes. But what about a substance that is able to determine the degree of solidity of a liquid?

As you well know, traditional gelatine serves this precise purpose but it tends to alter flavours and produce solids whose texture is not always so pleasant. This is because it is protein-based but, today, we are going to familiarize with a carbohydrate-based substance. We are talking about agar agar which derives from certain species of algae. It was discovered as long ago as the 1600s, even though a restaurant called El Bulli is responsible for its introduction to high class European cuisine. But what is agar agar and how to use it in cooking?

What is agar agar?

As mentioned above, what sets it apart from other substances of this type is the fact that it is composed of carbohydrates, mainly agarose and a little agaropectin. Agarose is a polysaccharide and therefore a sort of chain made up of repeating units of agarobiose, a disaccharide. It helps to know that this chain is what gives agarophyte algae their form. We can say that the jelly-like consistency of these algae, therefore, is due to the presence of agarose and agaropectin.

Over four centuries ago in Japan, it was discovered that agarophyte alga, when boiled, produces a substance which, duly filtered and dried, could be used to solidify any type of liquid. So, you can imagine agar as being a sort of net that is ready to trap liquid molecules and solidify them. Moreover, its jellifying capacity is so high that you need a far smaller amount than any other type of similar substance: in fact, 0.7-0.8% of its weight is sufficient to thicken a liquid, and the more you add, the denser it will become. The fact that such a small amount is required has some important effects: the liquid will retain its original appearance, its sensorial characteristics will be scarcely affected and the end product will be far more pleasing to the palate. There is a further characteristic which makes this ingredient even more interesting when applied to cooking.

Like all jellifying substances, before use, agar must be immersed in cold water, boiled, added to the other ingredients and left to cool. At this point, however, no matter what degree of solidity the end product has, it will only start to dissolve at 185 °C. This means that it will not melt in the mouth, offering a far wider scope than that of traditional gelatine.

How to use agar: pina colada dessert recipe

To enable you to appreciate the versatility of agar, here is an amazing recipe in which it is used: pina colada mousse. The basic ingredients of a cocktail, therefore, turned into a dessert. To make it, you will need one cup of coconut milk, one slice of pineapple diced into small cubes, 3 grams of agar in powder form (if you have cubes or sheets reduce them to a powder using a kitchen robot), one spoonful of lemon juice, two spoonfuls of sugar and one cup of whipped cream.

First of all, place the agar in a cup of cold water for at least 30 minutes. Mix the pineapple with one spoonful of the sugar and then heat a small saucepan containing the wet agar. Mix until it is well dissolved. In another pan, heat the remaining sugar and coconut milk on a low flame and, when the mixture reaches boiling point add the warm dissolved agar, continuing to stir for one more minute. Remove the pan from the heat and pour its contents into a bowl standing in ice, stirring vigorously for 8-10 minutes.

When the mixture has thickened nicely, add the pineapple, stir once more and serve in dessert bowls with a garnish of your choice. From liquid to solid, a delight for the palate!



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