The properties provided by the different types of carrageenans allow to achieve different sensory profiles in the end product, that are adapted to the specific preferences of each market; improving cohesiveness, consistency, appearance, cut, water retention and optimizing costs thanks to that this allows to reduce the content of total solids, protein and fat in the formula.
In the particular case of carrageenan, the molecules first adopt a simple helix conformation to which is added a second helix. The double helix formed in this way, constitutes the construction material of the three-dimensional structure.
Depending on the concentration and type of carrageenan in question, the three-dimensional structure can be visible to the human eye and possess mechanical properties such as firmness, resistance to the rupture, elasticity, among others. This is what is called gel.
As it is already mentioned in the section carrageenan, the properties of the gels depend on the specific type of carrageenan and can be reinforced by means of the synergy with other hydrocolloids or with proteins.
Carrageenans Kappa I, Kappa II and lota produce gels in water and in milk without the need of refrigeration.
The most attractive of carrageenan employment, as gel forming agent, is that by means of the combination of the different types is possible to obtain an endless number of textures; soft, elastic, firm and brittle.
The gels are stable at room temperature although they are thermo-reversible, since they present the phenomenon of hysteresis that consist in the difference of temperature between gel forming and melting; difference that in the case of carrageenans is very large, guaranteeing the maintenance of the shape of gelled products and their sensory properties even in conditions of high temperature.
In other cases, the structure is not visible, but it is detected with specific rheological methods and is what is called weak three-dimensional network.
The weak three-dimensional networks are very important because they are thyxotropic, i.e. when they are subjected to movement they flow and when this stops, they acquire again their structure, contributing to the immobilization of the components in the formula; being in liquid products an excellent action mechanism to obtain stability.
In general, at high temperature, carrageenan dispersions give low viscosity that facilitates the process; for example, pumping and packing of products without affecting the heat transfer speed.
The viscosity of carrageenan dispersions is given by the chemical structure , the poly-anionic nature, the high molecular weight and the conformation that these macromolecules acquire in aqueous medium, that is lineal without branches.
Of course, the viscosity also depends on the specific type of carrageenan, its concentration, temperature and the content and type of total solids. It has an exponential rise with the increase of concentration and molecules of bigger molecular weight and decreases with the rise of the content of total solids, mainly salts, temperatura and shearing forces.
In dairy systems, the three-dimensional network is the result of the protein-carrageenan interaction, while than in meat products carrageenan forms three-dimensional structures in the interstice, reinforcing the gel made up meat protein.
One of the most widespread applications, where carrageenan strongly dominates the market is in the suspension of particles of cocoa in chocolate milk and dairy drinks. This is possible thanks to the special reactivity of carrgeenans with the milk proteins previously described , that allows its use at very low concentrations as suspension agent.
Kappa II carrageenan reacts through two mechanisms:
- The viscosity supplied by carrageenan maintains the particles in suspension, preventing their sedimentation while the gel is forming
- Carrageenan reacts directly with the Kappa-casein of milk, forming a thixotropic gel, imperceptible to the palate that traps and maintains the particles in suspension
Due to the interaction between Kappa Casein and fat and cocoa powder, these elements enrich the three-dimensional network, contributing to the stability.
The main benefit of Kappa II carrageenan in comparison to Kappa I, is that its reactivity with milk proteins is “suitable” and moreover it provides viscosity and creaminess to the system, allowing to adjust the use dosage to the desired body easily and without the risk of undiserable clots formation when raising the used dose, therefore it results “appropriate” for dairy drinks that require mouth-feel and in milk shakes.
In spite of casein has a high thermal stability (121°C more than 30 minutes), it is not exempted of having thermal damage, especially when for any reason the product has to be sent back again to the termal treatment unit or dairy raw materials in powder, whose thermal stability has not been proven, are employed .
By itself carrageenan does not prevent the termal damaged of casein but it contributes to prevent the sedimentation of damaged protein by the mechanisms of viscosity contribution and the formation of a weak three-dimensional network and due to the lubricant effect provided, helps to reduce the perception of these particles in the palate.
What it has to be taken into account is that in situations of severe thermal treatment, the use dosage of carrageenan has to be reduced due to its interaction with whey protein increases, specifically with the -lactoglobulin, since this protein denatures thermically and to prevent a situation of undesirable clotting, it is advisable to lower the carrageenan use dosage.
This phenomenon is manifested by the separation of a layer of whey at the top, clearly visible and the loss of sensory properties, negatively affecting the quality of the product.
This problem is present especially in mixtures for soft serv ice cream during the period of storage that is of 4 weeks for pasteurized product and up to 3 months for the ultra pasteurized one.
To prevent this, it is necessary the employment of carrageenan , since it forms a three-dimensional network, where the double helices interact with milk protein, trapping the water and immobilizing it.
This three-dimensional network also contributes to the stability of suspension and emulsion, since it also immobilizes the suspended particles and the fat globules, obtaining in this way an homogeneous product that remains its whole shelf life.
This property is very appreciated in the food industry, since independent of the yield issue, the most important is the immobilization of water. This should not reach the surface of the product because there, in the presence of oxigen and nutrients, pollution can start microbial development and the alteration of the product.
Depending on the specific type of industry, different terminology is handled.
The meat industry talks about “humidity retention” for entire pieces such as restructured products, “drip loss” for marinated products, syneresis for fine pastes packed in pots as pâtés, terrines, mousses and “purge” for the sliced products vacumm-packed, which helps to break the structure, favoring the release of water.
In dairy products, only in the case of fresh cheese is talk about moisture retention and for the other categories the term syneresis is employed.
In all these cases, carrageenans contribute to prevent water losses.