Although its exotic name may puzzle some consumers, agar-agar has long been known in japan where consumption and use of algae for culinary purposes goes back centuries. The gelling substance was discovered by accident in 1658. A cook at an inn discarded some left-over gelidium seaweed soup served at dinner. It froze, thawed and dried during adverse weather before finally being found by its creator. He then boiled and cooled the residue and discovered that the resulting jelly had enhanced culinary properties.
It is still possible to find hand-made agar-agar. Although the current manufacturing process still uses the same basic steps (boiling, freezing, thawing, drying), it has however been adapted to modern industrial methods, which obtain a more stable and safer product through effective extraction methods. But the raw material remains the same as when agar-agar was first discovered: rhodophyceae, red algae, including several genera other than gelidium are now harvested (gracilaria, pterocladia, gellidiella).
In the industry, algae are first washed and then treated with an acid or an alkali to facilitate extraction or to increase the final product’s gelling capacity. The plants are then boiled under pressure, filtered and cooled. Next, two methods are used to extract water from the product: either a freezing and thawing process or mechanical pressure is applied to the gel formed upon boiling. Finally, the plant gum obtained is dried and then ground according to the desired form: powder, flakes, bars or threads.
The advantage of this polysaccharide for the food industry and cooking lies in its ability to form a reversible gel which, unlike a gelatin-based gel, requires a low concentration and allows greater flexibility in the temperature at which it can be used. In fact, agar- agar gel only melts at a temperature of around 194°f (90°c) and congeals faster once boiled, as soon as its temperature drops to about 104°f (40°c). When mixed with cold water, agar-agar is insoluble. When it is boiled in water, its polysaccharide linear structure curls and forms helices that then join a more complex arrangement, trapping the water upon cooling.
The result is a brittle, cloudy gel, which allows cooks to sculpt delicious liquid mixtures in many unusual forms such as spaghetti, beads, or thin, tasty sheets that can be rolled. Agar-agar also offers the advantage of not requiring the addition of molecules or other ingredients besides water, since agar-agar molecules bind together due to the hydrogen ions already present in water. In addition, this hydrocolloid can be used with various sugars, proteins and more acidic foods such as fruit. It is worth noting that the addition of large amounts of sugar, up to 60% of the solution, will further strengthen the gel. The use of agar-agar is definitely flexible, but you have to be careful: tannic acid found in squash, apples or plums may hinder the formation of the gel if they are used in large quantities in the gel preparation.