Hydrocolloids are substances often used in the stabilizing, thickening and gelling in food and other products. Hydrocolloids are large molecular weight polysaccharides that can gel through interlinking of their polymer chains. In gelation, water is trapped within an intertwined network of polymer chains. Hydrocolloids can gel in a variety of ways, including heat-cool cycling and the addition of chemical agents.
One such hydrocolloid, carrageenan, is a family of linear sulfated food grade polysaccharides typically obtained from red seaweed. Carrageenans are present in the seaweed as gels under natural environmental conditions and have the unique ability to form an almost infinite variety of gels at room temperature, rigid or compliant, tough or tender with high or low melting point. Carrageenan solutions can thicken, suspend and stabilize particulates as well as colloidal dispersions and water/oil emulsions. The solutions are pseudoplastic, but quickly rebuild viscosity and suspending power upon standing. Carrageenan can be used in a wide variety of foods, including sauces and gravies, processed meats and cheeses, chocolate milk, dressings, desserts, and the like.
The carrageenan family has three main types (known as kappa, iota and lambda), which are well differentiated in terms of their gelling properties and protein reactivity. Kappa carrageenans typically produce strong rigid gels, while those made with iota products are flaccid and compliant. Although lambda carrageenans do not gel in water, they can interact strongly with proteins to stabilize a wide range of dairy products. Exemplary chemical structures for kappa, iota, and lambda carrageenan are disclosed in A. Imeson, Thickening and Gelling Agents for Food, (Blackie Academic & Professional 1992), which is hereby expressly incorporated by reference as though set forth in full herein. Kappa and iota carrageenans form helical tertiary structures, which tend to destabilize in the presence of sulfate substituents (it is the higher percentage of sulfate groups in lambda carrageenan that is believed to prevent it from gelling).
Production of carrageenan typically begins with the extraction of the material from the seaweed with alkaline aqueous solutions at elevated (i.e. about 50° C.) temperature. After extraction, the carrageenan is clarified to remove cellulose, (typically by filtration), concentrated, and recovered (often through an alcohol precipitation on freeze-thawing technique). The carrageenan is then typically ground to a powder for use. Exemplary procedures are described in U.S. Pat. No. 6,063,915, the disclosure of which is hereby incorporated herein in its entirety. In many instances, different carrageenans are blended in known percentages (e.g., 45 percent kappa, 45 percent iota and 10 percent lambda) prior to use in food.
Preparation of a carrageenan gel has typically commenced with the dispersion of the carrageenan powder in cold water, which is then heated to a temperature above 75° C. to dissolve. The dissolution disentangles the polymer chains and uncoils the helices thereof. The solution is then cooled to form a gel, during which time the helices recoil, thereby causing the carrageenan molecules to entangle and cross-link (electrostatic bonding between the sulfate groups and ions in the solution can also occur). This cross-linking increases the ability of the carrageenan to gel.
In some instances, the gelation of the carrageenan solution (and, in turn, the thickening or other alteration of the foodstuff to which it is added) is carried out during the preparation of the food itself (for example, if carrageenan is used to thicken a pudding, the pudding and carrageenan are heated, then cooled, at which point the pudding gels). However, in some instances, it would be convenient if carrageenan would gel and thicken without undergoing heating. This behavior would also be desirable for ready-to-eat chilled foods. It would also be convenient if other hydrocolloids could be similarly prepared.