X-Carrageenan

O Neill (30) has shown that carrageenan is a mixture of at least five different polysaccharides. The two main components are x-carrageenan, which consists of sulfated n-galactose and 3,6-anhydro-n-galactose residues in a 1.2 (or 1.4) to 1 ratio, and A-carrageenan, which is almost entirely made up of a-... 

X-Carrageenan [9064-57-7], Ppted from a soln of 4g in 600ml of water containing 12g of potassium acetate by addition of EtOH. The fraction taken, ppted between 30 and 45% (v/v) EtOH. [Pal and Schubert JACS 84 4384 7962]. 

Model building in the computer is used to analyze the conformational effects of steric interactions between atoms of the polymer skeleton for x-carrageenan, t-carrageenan, A-carrageenan, agar, chondroltin, chondroitin sulfates, dermatan sulfate, keratan sulfate, hyaluronic acid, and related polysaccharides. Over 99% of the conformations are thus excluded and virtually all of the remainder for each polysaccharide lie close together. Predictions are also made from disaccharide crystal structures and checked against experimental results. 

Fig. 3. —Comparison of the Variation of Optical Rotation with Temperature for Native -Carrageenan (—) and Segmented x-Carrageenan (—) in the Presence of Locust-bean Gum. [Heating and cooling curves are distinguished by the arrows. Measurements were made at 546 nm with solutions that were 1 % with respect to locust-bean gum and 2% with respect to carrageenan. The gel point (G) and liquefaction point (L) are shown.]...

In aqueous solutions at elevated temperature, carrageenans exist as random coils. On cooling, a three-dimensional polymer network builds up, in which double helices of x-carrageenan form junction points of the polymer chains. 

In combination with galactomannans, x-carrageenan shows an unusual synergism, which is marked by an enhancement of the gel strength. This phenomenon is believed to be due to a carrageenan-galactomannan interaction. 

Mainly the gel-forming properties of x-carrageenan are used for pharmaceutical purposes. Due to the high viscosity of the. -carrageenan, it is employed as an emulsifying and stabilizing agent. 

Lipolysis in milk is affected by inhibiting and activating factors. As discussed above, proteose peptone fraction of milk can inhibit milk LPL while apolipoproteins stimulate the enzyme. This is particularly important in spontaneous lipolysis however, proteose peptone 3 has been shown to inhibit lipolysis induced by homogenization, sonication, and temperature activation (Arora and Joshi, 1994), while protein components of the milk fat globule membrane inhibit lipolysis caused by bacterial lipase (Danthine et al., 2000). Several exogenous chemical agents can also inhibit lipolysis (Collomb and Spahni, 1995). For example, polysaccharides such as X-carrageenan at 0.3 g/1 effectively inhibits lipolysis in milk activated by mechanical means or temperature manipulation (Shipe et al., 1982) and lipolysis caused by the lipase from P. fluorescens (Stern et al., 1988). 

C. J. Lawson and D. A. Rees, Carrageenans. Part VI. Reinvestigation of the acetolysis products of X-carrageenan, revision of the structure of a-l,3-galactotriose , and a further example of the reverse specificities of glycoside hydrolysis and acetolysis, J. Chem. Soc. C (1968) 1301-1304. 

J. Prado-Femandez, J. A. Rodriguez-Vasquez, E. Tojo, and J. M. Andrade, Quantitation of K-, i- and X-carrageenans by mid-infrared spectroscopy and PLS regression, Anal. Chim. Acta, 480 (2003) 23-37. 

Tarrega, A., Costell, E., and Rao M. A. 2006. Vane yield stress of native and cross-linked starch dispersions in skim milk effect of starch concentration and X-carrageenan addition. Food Sci. < Tech. Int. 12(3) 253-60. 

Michon, C., Cuvelier, G., Launay, B., and Paiker, A. 1996. Viscoelastic properties of X-carrageenan/gelatin mixtures. Carbohydr. Polym. 31 161-169. 

Zhang, J. and Rochas, C. 1990. Interactions between agarose and x-carrageenans in aqueous solutions. 

X-Carrageenan (lambda-carrageenan) is a nongelling polymer containing about 35% ester sulfate by weight and no 3,6-anhydrogalactose. 

In the case of topical gels, a combination of i, K-, and X-carrageenans produces a spreadable gel with acceptable tactile sensation, resulting in drug release that is more likely to follow diffusion kinetics. 

In the present work we have studied the dynamics of formation and structure of the air-water interface in the presence of (3-lg - - PS at 20°C and at pH 7 in a drop tensiometer. As PS with interfacial activity we have used propylene glycol alginates (PGA). To evaluate the effect of the degree of PGA esterification and viscosity, different commercial samples were studied. Xanthan gum (X) and X-carrageenan (X-c) were studied as nonsurface active polysaccharides. 

Even in the presence of potassium chloride, /x-carrageenan has little, if any, tendency to gel. 

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