Κ-carrageenan Solutions Research Articles

Growth and Viability of Bifidobacterium bifidum in Cheddar Cheese

Bifidobacterium bifidum (ATCC 15696) was grown in MRS broth containing cysteine HCl at 37°12, and the cells were harvested by centrifuging at 1300 x g for 15min at 4°C. Equal volumes of the cell slurry and a 2.5% solution of κ-carrageenan were mixed and transferred by drops into a solution of .3 M KCl at 20°C under an atmosphere of nitrogen. The gelled beads were separated, frozen, and lyophilized immediately. This preparation and a commercial powder preparation were added to Cheddar cheese curd at milling as two treatments. Treatments did not affect cheese composition. Soluble protein increased during ripening at 7°C but without differences between treatments; SDS-PAGE patterns of proteolysis were also similar. Lactic acid content of cheeses increased during ripening, but differences between treatments were minor. Acetic acid and ethanol, common metabolites of bifidobacteria, were not detected during ripening. Bifidobacteria remained viable and increased in numbers in cheese during this 24-wk study but did not affect the flavor, flavor intensity, texture, or appearance of the cheese compared with that of the control.

Sol-Gel transition of κ-Carrageenan as viewed through NMR

Abstract 23Na, 87Rb, and 133Cs NMR spectra were observed to study an interaction between these cations and κ-carrageenan. It was found that the NMR intensity of gel-forming cations undergoes a remarkable change in the vicinity of the sol-gel transition temperature, while the non-gel-forming cation which coexists together with a gel-forming cation does not show any change. These results suggest that gel-forming cations selectively interact with κ-carrageenan. Motion of water molecules in the gel and the solution of κ-carrageenan was studied by measuring the water proton spin-spin relaxation time. The results indicate three different types of water molecule: a free bulk water molecule, a water molecule strongly bound to κ-carrageenan, and a water molecule weakly bound to the gel network.

Diffusion and interaction in gels and solution. 5. Nonionic micellar systems

Studies are presented on the nonionic micellar systems hexaethylene (C 12 E 6 ) and octaethylene (C 12 E 8 ) glycol dodecyl ether in gels and solutions of κ-carrageenan. Aggregation numbers and size distributions of the micelles were studied with a fluorescence quenching method, while self-diffusion coefficients of the surfactants were determined with a tracer technique. It was found that the interaction between the surfactants and the polymers was repulsive, as revealed by a slight increase in micelle size in the presence of polymers

Rheology and fracture of mixed ι- and κ-carrageenan gels: Two-step gelation

It is shown that under certain circumstances, on cooling mixed ι- and κ-carrageenan solutions, the two forms gel separately at different temperatures, with the ι form gelling first. This ‘two-step gelation’ was only observed when both sodium and potassium ions were present, with a sodium/potassium mole ratio of between 1 and 100. For such mixed gels, a κ fraction as low as 2·5% of the total carrageenan has significant effects on their rheology, both at low deformation and fracture. In these systems, the κ form, gelling in the presence of an existing ι gel, produces measurable rheological effects at much lower concentrations than if it were alone. This behaviour can be used as a sensitive test of the ‘rheological purity’ of samples of ι-carrageenan.

Static light scattering from κ-carrageenan solutions

The polyelectrolyte behaviour of κ-carrageenan in NaCl and NaI solutions was investigated by static light scattering experiments. The solution properties of κ-carrageenan were found to be dependent upon the way the solutions were prepared. The dependence of the z-average radius of gyration and the second virial coefficient upon salt concentration exhibits normal polyelectrolyte behaviour in NaCl solutions for the range of ionic strengths considered. The persistence length as determined in the absence of long range interactions is found to be similar to values obtained for the majority of other polysaccharides. Within the same constraints of ionic strength a conformational change of the polymer chain is observed in NaI solutions without a noticeable change in molar mass. This observation is supported by measurements of optical rotation and the intrinsic viscosity.

Interaction of .BETA.-casein and .KAPPA.-carrageenan. I. Viscosity and turbidity under non-gelling conditions.

The relationship between gelling and casein stabilizing ability of κ-carrageenan was investigated using viscosity and turbidity measurements. At low ionic strength, 0.5% β-casein decreased the viscosity of 0. 1 % κ-carrageenan solution in the absence of calcium. In the presence of calcium, the viscometric behavior of κ-carrageenan-β-casein mixture was governed by the properties of β-casein rather than that of κ-carrageenan. A 0.1% κ-carrageenan solution formed a structure above 5 mM.CaCl2 at 5°C. Under the same conditions, the mixture began to gel at lower concentration of calcium than 5 mM. These phenomena suggested the participation of β-casein in the formation of the κ-carrageenan structure.

Conformational transition and aggregation of ϰ-carrageenan macromolecules in solution

Consideration has been given to the processes of conformational transition and aggregation in the aqueous solutions of ϰ-carrageenan depending on its concentration, the temperature of the system as a whole and the content of the potassium ions by the methods of polarimetry and spectroturbidimetry. It has been established that one and the same degree of mutarotation can be attained on variation of the concentration of both ϰ-carrageenan and potassium ions. The aggregation of the ϰ-carrageenan macromolecules occurs under the action of the potasssium ions and is independent of temperature.

On the sol-gel transition in solutions of Kappa-carrageenan

The disorder-order transition, which takes place at the gelpoint of κ-carrageenan solutions was monitored by optical rotation and light scattering measurements. The coincidence of both sets of experimental data affords good evidence that the sol-gel transition is accompanied by a conformational change. Transition temperatures were observed to be linearly dependent on the logarithm of the salt concentration and this result is explained by the formation of double helices. Heats of gelation were measured by differential scanning calorimetry. It was found that the enthalpy increases with ionic strength, which was ascribed to the occurrence of a secondary process in which double helices are assembled into larger aggregates.

The effect of simple electrolytes on the sol-gel transition of kappa-carrageenan

Summary The sol-gel transition in solution of κ-carrageenan to which different electrolytes had been added, was followed by light scattering. It was found that the gelling temperature is linearly dependent on the square root of the electrolyte concentration. Specific ionic effects on the sol-gel transition appear to be of minor importance. A simple electrostatic theory is presented to account for the √c-relationship.