Calcium or potassium salts are needed to obtain water gel, but they are not necessary for milk gels. This gelling mechanism is basic for kappa and iota carrageenan solutions. The presence of kinks in the chain, as well as the quantity, type and position of ester sulfate groups have important effects on gelling properties. Further cooling leads to aggregation of these junction points to build a three-dimensional gel structure. On cooling of the solution, a three-dimensional polymer network builds up in which double helices form the junction points of the polymer chains. ![]() At temperatures above the melting point of the gel, carrageenan polymers exist in solution as random coils. This phenomenon occurs due to the formation of a double helix structure by the carrageenan polymers. Hot aqueous solution of kappa and iota carrageenans have the ability to form thermo-reversible gels upon its cooling. Iota and lambda carrageenan are soluble hot. Concentrated Salt SolutionsĪll carrageenan types are insoluble in concentrated salt solutions (20% to 25% of sodium chloride) at room temperature. Iota carrageenan is only sparingly soluble in concentrated sugar solution at any temperature. However, kappa and lambda carrageenan are soluble in sucrose solutions as high as 65%, at temperatures above 70✬. Concentrated Sugar SolutionsĪll carrageenan types are relatively insoluble in concentrated sugar solutions at room temperature. Kappa and iota carrageenan are insoluble in cold milk, but may be used efficiently to thicken and/or gel cold milk solutions when used in conjunction with a phosphate such as tetra-sodium pyrophosphate (TSPP). Lambda carrageenan is soluble in cold milk, due to its insensitivity to the presence of potassium and calcium ions. The strength of the gel and its consistency depend on the solution concentration and the sensitivity of the carrageenan to calcium ions. On cooling all of these solutions tend to gel. Hot MilkĪll carrageenan types are soluble in hot milk but some types are strongly affected by calcium ions presence. Potassium and calcium salts from kappa and iota type carrageenan are not soluble in cold water, but will swell as a function of concentration and type of cations present as well as water temperature and condition of dispersion. In cold water, only lambda-carrageenan and the sodium salts of kappa and iota carrageenan are soluble. The normal amplitude of solubility temperature is between 40º and 70º C, depending on the solution concentration and the presence of cations. Chondrus and Gigartina skottsbergii are obtained respectively from natural seaweed beds in the North Atlantic and in Chile.Īll carrageenan types are soluble in hot water at temperatures above its gel melting temperature. Kappaphycus Alvarezii (Cottonii) and Eucheuma Denticulatum (Spinosum) seaweeds have been successfully cultivated on a commercial scale in the Philippines, Indonesia and Tanzania. After being harvested, seaweeds are placed under the sun to dry until they reach a humidity level that is ideal for processing. Seaweeds are usually harvested manually by fishermen in low depths at low tides or by diving using appropriate equipment. Some species like Chondrus Crispus and Gigartina skottsbergii produce mixed type carrageenan kappa/lambda or kappa/iota. The species that produce lambda type carrageenan generally belong to the Gigartina species. ![]() The specie that produces iota-type carrageenan is Eucheuma Denticulatum (former Eucheuma Spinosum). The species that produce kappa-type carrageenan are Kappaphycus Alvarezii (former Eucheuma Cottonii) and Hypnea Musciformis. Some species of seaweed may produce a mixed type carrageenan such as kappa/iota, kappa/lambda or iota/lambda. Seaweeds of different species and sources produce different types of carrageenan such as kappa, iota and lambda. The carrageenan content of commercial seaweeds varies from 20% to 40% of dry weight, depending on the seaweed species and the sea conditions, such as luminosity, nutrients, water temperature and oxygenation. Carrageenan is obtained from several kinds and species of seaweeds belonging to the Rodophyceae class.
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