Alginate is an ionized linear polymer, consisting of guloronic and mannuronic acids. It is mainly used to bind water and impart texture in food, pet food and non-food applications. The use of Alginate in food products can be traced back to more than a century ago. Its use in the production of food has steadily and dramatically increased over the last 30 years.
Types and Qualities of Alginate:
- Alginic acid (E400)
- Sodium Alginate (E401)
- Potassium Alginate (E402)
- Ammonium Alginate (E403)
- Calcium Alginate (E404)
- Propylen Glycol Alginate (E405)
Each Alginate originates from the same type of seaweed, however it is the extraction process that leads to the different types of alginate. Sodium Alginate (E401) and Calcium Alginate (E404) are the most commonly used in food products. The following theory will focus on Sodium and Calcium Alginate.
Sodium Alginate dissolves at ambient temperatures and gels instantly when divalent ions, like calcium or magnesium, are added to the solution. The gel is thermo-irreversible, which is desired in some applications. If monovalent ions are added to the Sodium Alginate solution, it will still create a gel, but the gel will be soft, spreadable and thermo-reversible.
Calcium Alginate is typically used in combination with other Alginate types or sequestrants. It creates everything from a thixotropic liquid to a firm gel depending on the conditions. The dose/usage level of Alginate and the ratio of water determine the amount of liquid that can be bound and the texture characteristics of the finished product.
In many applications, Alginate can do much more than just bind water. It can also:
- Provide heat stability
- Provide a specific texture
- Increase sliceability
- Provide body to an application e.g. as a fat replacer
- Improve flavour release
- Provide freeze/thaw stability
Alginate is extracted from the family of brown seaweeds known as Phaeophyceae. It is regarded as a texturizing ingredient and can be used in quantum satis (the amount which is needed) in food products worldwide.
- It conforms to FDA (Regulations 21 CFR 184.1724) and the Food Chemicals Codex standards. We recommend that the food manufacturer using the product ensures that this product is in compliance with the local regulations in force, particularly in the country where the finished product is to be consumed.
- It conforms to EU regulation 2012/231/EU, the Code of Federal Regulations and the Food Chemicals Codex standards. We recommend that the food manufacturer using the product ensures that this product is in compliance with the local regulations in force, particularly in the country where the finished product is to be consumed.
As described earlier, Alginate is an extract from brown seaweed. The species of seaweed is one of the determining factors of the type and functionality of the Alginate.
- Laminaria (also called Kelp) is a wild growing, cold water seaweed. This has a high concentration of guloronic acid which creates firm and brittle gels.
- Lessonia (also called Kelp) is a wild growing, cold water seaweed. This has a high concentration of manuronic acid which creates strong and elastic gels
Both seaweed types tend to grow in water at a depth of approx. 8 meters and are manually harvested and dried thereafter.
The production of differs according to Alginate type. We will focus on the most important:
- Calcium Alginate
- Sodium Alginate
In the process to obtain Alginate, the dried seaweed is washed and the Alginate is extracted by use of hot water and sodium carbonate. This Alginate slurry is filtered in order to get rid of the insoluble cellulose and other impurities. The cellulose + minerals from the process + filter aids are typically used for field fertilization in local areas. The hot Alginate slurry contains a great quantity of water. The water is usually removed by:
- Addition of Calcium. The Alginate will precipitate as Calcium Alginate. The precipitated Calcium Alginate is filtered away from the water. The remaining water is evaporated by hot air. The dry material at this point, is milled into Calcium Alginate powder.
- If acid is added, the Calcium Alginate dissolves and turns into Alginic Acid. When sodium carbonate is added to the Alginic Acid, it is neutralized and turns into Sodium Alginate. The Sodium Alginate is filtered away from the slurry. The remaining water is evaporated by hot air. The dry material from here is milled into Sodium Alginate powder.
As mentioned before the Alginate is a polymer containing guloronic and mannuronic acids.
- Laminaria, high amount of guloronic acid, low amount of mannurinic acid (high G, low M). High gel strength, brittle gel
- Lessonia, low amount of guloronic acid, high amount of mannuronic acid (low G, high M). Low gel strength, elastic gel
The guloronic acid is a negative charged (1-4) α –L-guleronate, which interacts with the positive charged ions. Divalent ions, such as calcium, cross link the molecules into a strong three dimensional network. The α linkage between the molecules orient the molecules into “hills” and “valleys”. The calcium ion links the “valley” from one molecule to the “valley” from the other molecule causing the Alginate to gel.
The mannuronic acid is a negative charged (1-4) β-D-mannurate, interacting as well as the guluronic acid with other ions, but to a much lesser degree. The β linkage creates a more linear molecule without “hills” and “valleys”. This explains in part why the Alginate type has soft and elastic gel properties.
It is very important to underline that Laminaria is not purely guloronic acid and Lessonia is not purely mannuronic acid. In both cases, there exists a combination of guloronic and mannuronic acid. The proportion and placement of the two acids varies according to the age of the seaweed, the seaweed quality and the area of harvest.
Gelling salts + synergistic gums
Alginate cannot achieve its maximum functionality without gelling ions, in practice known as gelling salts. Some gelling salts are more efficient than others, e.g. Calcium is very efficient to create a firm thermo-irreversible gel. Others, such as monovalent ions will encourage the Alginate to gel more softly into a thermo-reversible gel.
- Most important gelling ions in falling order: Ca++, Mg++, K+, Na+, H+
Typically, when Alginate is combined with other ingredients, a superior ‘gain’ or ‘potentiation’ is achieved. This can be explained as an a supporting effect. Explanations: Starch, guar gum and xanthan gum do not chemically interact with the Alginate molecule, but can optimize the distribution of the gelling salt allowing the Alginate to gel more homogenously, in a gelling jar.
Main functionality in applications
The main functionality of Alginate is to bind water. Hereafter, it may also have a secondary function to modify the texture of the gel according to specific requirements. All Alginates are stable and easy to use in a wide spectrum with regard to:
This makes Alginate suitable in most common food products or in other non-food products where water must be controlled.
Alginate is typically applied in one of the 3 examples below.
External setting: A Sodium Alginate solution is made, e. g. together with aromas and colours. How it works: The solution is treated directly with calcium. The Alginate gels instantly. Application example: artificial caviar and co-extruded sausage casing.
Internal setting: The Alginate is incorporated into a food application. The other raw materials in the food application contain the necessary ions and cause the Alginate to gel. Application examples: custard crème, jam and fruit fillings.
Internal setting or a self-gelling system: The Sodium Alginate is combined with a gelling salt and a gelling retardant. This is a balanced triangle of e.g. sodium Alginate, calcium sulphate and phosphate. How it works: when the system is hydrated, the Alginate dissolves. The Alginate gels hereafter with the calcium ions, which are released from the calcium sulphate. The phosphate controls the gelling speed. Too fast a gelling speed results in gelation in the mixer and the mixer action will break up the forming gel. This is called pre-gelling. When the mixer is emptied, it will be a highly viscous solution. This solution is a broken gel and cannot ‘re-gel’. If the pH value is lowered, the calcium ions will be release quicker from the calcium sulphate. This speeds up the gelling time. In other words, the composition of a self-gelling system needs to be balanced for a specific application in order to optimize the performance in terms of gel strength and gelling time. Application examples: fat emulsion, restructured meat and nuggets.
EUROGUM standardizes and mixes Alginates in order to ensure and secure consistent product performance. Alginate is a natural product and it is our expertise that allows us to consistently deliver on an established specification without variance. The performance of our products in your processes and in your finished products remains the same from batch to batch.
The performance of an Alginate product depends on, but is not limited to:
- Type of seaweed
- Age of seaweed
- Ion composition
- Viscosity of Alginate
- Process in general
- Mesh size of the powder
- Additional gelling salts and sequestrates
- Addition supporting gums
All these factors are important to consider when a new product is developed. This product can be developed as a result of a matching of an existing product, but also as a new product developed from scratch. EUROGUM specializes in producing customized blends, for all applications, with short delivery times, in order to satisfy the requirements of all our customers.