All carrageenan are dispersible in cold water, and when heated above 80C they are completely dissolved. During cooling process Kappa and Iota carrageenan form double helix molecular structures cross-linked by potassium and calcium ions, forming a tridimensional gel-type network.
Synergies
of Carrageenan in Starch Based Systems.
Carrageenan is obtained by extraction with water or alkaline water of
certain species of the class Rhodophyceae (red seaweed). Important species
are Eucheuma cottonii, which yields kappa-carrageenan, and Eucheuma
spinosum which yields iota-carrageenan.
Carrageenan shows thixotropic behavior. Carrageenan solutions and gels are stable at neutral and slightly acid system. The combination of elevated temperature and acid conditions will produce hydrolysis of carrageenan resulting in a loss of viscosity and/or gel strength.
In meat systems, carrageenan helps to retain water in the interstitial spaces of the gel formed, achieving a higher hardness in the final product.
Carrageenan
have strong interaction with milk proteins, being able to form very
firm gels at very low concentrations. This synergism is given by the
direct interaction between carrageenan and k-casein. This interaction
takes place in a wide range of pH and is strengthened by cations.
Carrageenan increase the hardness, brittleness, gelation and melting
temperatures of their gels in water with the addition of potassium and
calcium ions.
Sodium and potassium salts of polyphosphates and
citrates enhance solubility of carrageenan in cold and hot solutions
and reduce their viscosity due to divalent cations chelation.
Synergism with Starch Iota carrageenan increases the viscosity of
starch systems by as much as 10 times the viscosity of the starch alone.
When kappa carrageenan is added to starch systems no increase is noted.
Carrageenan has a strong functional synergism with starches and can
be used in starch-based foods to retain moisture. Mixed carrgeenan/starch
systems have unique properties which are a cost-effective answer to
improving the quality of high starch formulations. The strong functional
interaction between starch and carrageenan allows the starch content
of soups, pie fillings and pudding to be reduced whilst improving the
organoleptic properties of the system. Additionally, starch/carrgeenan
combinations offer resistance to shear degradation and low processing
viscosity while maintaining excellent stability during thermal cycling.
| Figure compares the effects
of shear on a starchonly system with starch/iota carrageenan
and starch/kappa carrageenan systems. The starch system exhibits
a loss in its viscosity when subjected to shear. The presence
of 0.5% kappa or iota carrageenan allows a starch system to
recover its pre-shear viscosity.
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