Carrageenan lambda-type

The lambda type is nongelling, and functions as a thickner. Iota-carrageenan has been recommended (45) for use in formulating low fat ground beef due to its abihty to retain moisture, especially through a freeze—thaw cycle which is typical for ground beef patties. Oat bran and oat fiber can also be used to improve moisture retention and mouth feel. Modified starches can be used as binders to maintain juiciness and tenderness in low fat meat products. Maltodextrins (dextrose equivalent less than 20) may be used as binders up to 3.5% in finished meat products. Other carbohydrates such as konjac flour, alginate, microcrystalline cellulose, methylceUulose, and carboxymethylceUulose have also been used in low fat meat products (see CELLULOSE ETHERs). 

During cooling of hot solutions of /c- or t-type carrageenans, gelation occurs because the linear molecules are unable to form continuous double helices due to the presence of structural irregularities. The linear helical portions then associate to form a three-dimensional network in the presence of the appropriate cation. All salts of lambda-type carrageenans are soluble and non-gelling. 

The three preferred carrageenan t3q>es are kappa, iota and lambda. The kappa and iota types only dissolve in a heated water medium, whereas the lambda type is soluble in cold water. Gels created from different carrageenan types may be fluid, elastic or rigid and are heat-reversible. Gelling temperatures and gel strength are also influenced by added ingredients such as salts and proteins. 

All of them are soluble in hot water but form gels on cooling, except the lambda type which remains wate soluble at low temperature. Emphasis will be placed below on the properties and characterization of 1,- and K-carrageenans. 

Lambda ( -type) carrageenans have found use as thickeners [78]. The carrageenans have been found suitable to be utilized as gelling, thickening, suspending [24] and sustained release agents [4]. 

Commercial carrageenans are composed primarily of three types of polymers kappa-, iota-, and lambda-carrageenan. 

Carrageenan products, of which a large number are usually available from a single supplier for different specific applications, contain different proportions of the three main behavioral types (kappa, iota, and lambda) produced by starting with mixtures of red seaweed species. Other substances, such as potassium ions and sugar (for standardization), may be added to the obtained powder to produce the commercial product. 

Carrageenans are anionic polyelectrolytes prepared from red seaweed. There are three types k- (kappa), i- (iota), and 1- (lambda) carrageenan commercially available (Figure 26.3). 

Lambda does not gel and is used to thicken dairy products. It has an ester sulfate content of about 32-39 % and no content of 3, 6-AG. X-type is readily soluble in cold or hot aqueous solution. X-carrageenan exhibits the highest antioxidant and free radical scavenging activity. 

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