How do we obtain red algae extract, also known as carrageenan?

Carrageenan is a biopolymer extracted from red algae, or Rhodophytes. These are marine algae primarily found in Europe (Atlantic Ocean, English Channel, North Sea). There are various varieties of red algae, such as Chondrus crispus, Mastocarpus stellatus and Furcellaria fastigiata.

Little anecdote : The name "carrageenan" comes from the Celtic "lichen carraghen" meaning "Irish moss". Sailors used to use it to make jellied desserts by adding handfuls of bleached seaweed to their milk.

Today, these compounds are still present in the food industry but are also widely found in skin and hair care. Carrageenans are sulphated polysaccharides that serve to thicken formulas and give them a consistency of a gel. Indeed, they present sulphated D-galactose residues. In contact with water, these biopolymers unfold and form a gel network. Furthermore, carrageenans also have benefits for the skin. They are humectants, meaning they have the ability to retain water, improving the overall appearance of the skin. They are also capable of stimulating the natural production ofhyaluronic acid and ceramides, strengthening the skin's barrier and limiting insensible water loss.

The process of extracting carrageenans from red algae involves several steps detailed below:

1. Red algae are harvested, cleaned to remove sand and non-algal residues, and sun-dried. The moisture content should not be less than 35% in order to preserve the quality of the carrageenans, whilst preventing the algae from deteriorating;

2. The algae, once dried, then undergo vigorous mechanical agitation in a warm, aqueous alkaline environment (presence of sodium or calcium hydroxide or sodium carbonate). These basic conditions ensure the formation of 3,6-anhydro bonds between the polymeric chains, which increases the gelling capacity of the carrageenans;

3. The reaction medium is filtered directly or centrifuged to eliminate all insoluble residues;

4. The solution obtained is then concentrated through evaporation or ultrafiltration;

5. A precipitation reaction in an alcohol (most commonly isopropanol) or with potassium chloride allows for the recovery of carrageenans in a solid form;

6. The carrageenans are pressed to rid as much liquid as possible, then dried and ground. This results in a powder that typically yields a high return of about 25% compared to the initial mass of dry seaweed.