Carrageenan Concentration Research Articles

Carrageenan–oligochitosan microcapsules: optimization of the formation process

The formation of new microcapsules based on polyelectrolyte complexes between carrageenans and oligochitosan has been investigated. The optimization of the process, which includes the selection of the most suitable solvent and investigation of the influence of reaction conditions on capsule properties, is presented. Iota-carrageenan (1.2–2% wt.) prepared in HEPES buffer was found to be the most suitable for the formation of mechanically stable capsules. These new capsules combine extremely high deformability (>90%) and elasticity with permeability control and can be applied in various bioencapsulation technologies. It has been shown that the reaction time influences the mechanical properties, whereas carrageenan concentration and the temperature during the capsule formation effect both mechanical and porosity characteristic of the membrane. Moreover, the temperature influences the kinetics of the diffusion through the complex iota-carrageenan/oligochitosan membrane. In general egress is faster above the sol–gel transition point, indicating applicability in thermo-induced releasing systems.

Effect of the concentration of agar, alginate and carrageenan on the stability, toughness and nutrient leaching in artificial diets for abalone

In order to evaluate the effect of different binders on the quality of artificial diets for abalone in terms of stability, nutrient leaching and toughness, three phycocolloids (agar, alginate and carrageenan) were used at different concentrations (0.5%, 1.0%, 1.5%, 2.0% and 2.5%), mixed with fish meal or abalone viscera silage as protein sources. Both stability and pellet toughness were influenced more by the protein source than by the type and concentration of the binder, as diets containing abalone viscera silage lost 20% dry matter, compared to the 10% lost in diets containing fish meal. However, nutrient leaching was not affected by the phycocolloid concentration. This result coincides with previous reports that leaching speed does not depend on stability. In general, all the binders used were effective at low concentrations (0.5%); therefore, the use of phycocolloids at low concentrations is recommended. Attention should also be given to the ingredients used, as these may have a greater influence on stability and toughness than the binders themselves.

Viscoelastic properties for kappa- and iota-carrageenan in aqueous NaI from the liquid-like to the solid-like behaviour

The dynamic mechanical behaviour of a series of concentrations of kappa-carrageenan (KC; 0.35–1.6% w/w) and iota-carrageenan (IC; 0.2–1% w/w) in 0.2 M NaI has been investigated. The flow behaviour of KC within the concentration range 0.004–0.8% (w/v) was also described. The high intrinsic viscosity of KC in 0.2 M NaI (23.4 dl g −1) and the great increase in viscosity with increasing concentration, in comparison with linear flexible polysaccharides, is well consistent with the stiffness of KC helices in NaI. The variation of the ‘zero-shear’ specific viscosity of KC in 0.2 M NaI with the degree of space-occupancy ( c[ η]) displays two critical concentrations at c*≈0.09% w/v ( c*[ η]≈2) and c**≈0.4% w/v ( c**[ η]≈10). Different viscoelastic behaviours were exhibited from the liquid-like to the solid-like depending upon the type of carrageenan. From the application of the time–temperature superposition, classical frequency–temperature master curves could be obtained for KC, but not for IC. Moreover, for KC, a concentration–frequency master curve could be constructed for the concentrations below 1.5%, indicating a ‘solution-like’ behaviour in this entire concentration range, although systems above 0.8% were visually gel-like. It is proposed that the rigidity of the KC helices is responsible for the slow relaxation rates of the gel-like samples. At higher concentrations (beyond 1.6%) a frequency–temperature superposition was no longer possible. In contrast to KC, IC behaved as a typical viscoelastic gel with a very weak frequency dependence of the storage modulus at all temperatures. This indicates the existence of associations beyond simple entanglements for IC. Creep experiments performed at higher carrageenan concentrations in 0.1 M NaI further corroborated the differences in the viscoelastic behaviour between KC and IC.

Phase behaviour of pure micellar casein/κ-carrageenan systems in milk salt ultrafiltrate

The phase behaviour of pure casein micelle/κ-carrageenan/water systems has been studied using turbidimetry, microscopy and rheology. The phase state diagram of these systems has been established at 5 and 60°C and the mechanisms are discussed. There is a significant difference between the phase diagram at 5°C and at 60°C in relation to the carrageenan concentration. At a temperature of 5°C, the data demonstrate that, depending on the relative amount of each component, the system behaves like a liquid, which can be either stable or unstable. Polymer adsorption on casein micelles at low κ-carrageenan concentration is suggested. This phenomenon is followed by depletion at higher concentrations. Interestingly, this later instability occurs at a very low concentration of κ-carrageenan (∼0.01%, w/w). As the κ-carrageenan concentration increases, the system gets trapped into a gel state. It is proposed that a casein/κ-carrageenan composite network is formed in which κ-carrageenan molecules act as bridges between casein particles. At a temperature of 60°C, when carrageenan chains adopt a coil conformation, depletion flocculation occurs when the concentration of carrageenan is around 0.3% (w/w).

Effects of carrageenan type on the behaviour of carrageenan/milk mixtures

The apparent hydrodynamic diameter of casein micelles was determined as a function of hydrocolloid concentration at 60°C and during cooling to 20°C. The systems studied contained skim milk 100-fold diluted in permeate in the presence of either lambda-, iota-, kappa-carrageenan or guar gum. These measurements show that all three forms of carrageenan adsorb onto casein micelles, whereas guar gum does not. Lambda-carrageenan (which is always in the coil conformation) adsorbs at all the temperatures studied, whereas the iota and kappa forms adsorb only at temperatures below the onset of the helix–coil transition. The results agree with the idea that adsorption of carrageenan occurs only above a certain minimum charge density. Phase diagrams were established at 60°C for the three carrageenans and the rheological behaviour was followed on cooling and at 25°C. The results suggest that the lambda-carrageenan bridges the casein micelles at low carrageenan concentrations, leading to the sedimentation of carrageenan/milk mixtures at 60°C and structure formation on cooling. At 60°C, iota- and kappa-carrageenan induce depletion flocculation of casein micelles above a critical carrageenan concentration. On cooling, systems containing iota-carrageenan clearly form a network at the helix–coil transition temperature. The network is formed by mixed carrageenan/casein micelle crosslinks. In the presence of excess carrageenan, this network is reinforced by carrageenan/carrageenan crosslinks. For the kappa-carrageenan/casein micelle mixtures the existence of mixed carrageenan/casein micelle crosslinks is less obvious but seems likely.

Gel formation in heat-treated bovine serum albumin– κ-carrageenan systems

The effect of different concentrations of κ-carrageenan on the gel strength, gelation kinetics, and gel microstructure of bovine serum albumin (BSA) gels was investigated at different conditions of pH and ionic strength with and without the addition of potassium chloride. Two types of strengthening effects were observed: a major strengthening effect at the isoelectric point of BSA and slightly above, low ionic strength, and high carrageenan concentration (∼0.4–1.0% (w/v)); and a minor strengthening effect at higher pH and all ionic strengths at lower carrageenan concentration (∼0.2–0.4% (w/v)). The liquid that could be removed from the gels by centrifugation had a lower carrageenan concentration than the original gels at low pH and ionic strength, suggesting associative phase separation. The gelation kinetics of these gels differed from that of pure BSA or carrageenan gels, suggesting strong interactions between the polymers. At high pH or ionic strength, the gel centrifugates were enriched in carrageenan, and the gelation and melting of carrageenan could be observed in the heat-denatured BSA– κ-carrageenan gels by dynamic oscillation measurements. These effects are explained by segregative phase separation. The results also show that the presence of potassium ions during the gelation of BSA is important for the strengthening effect at associative conditions. This strengthening effect was observed up to higher pH values when sodium ions were partly replaced by potassium ions, and vanished completely when the potassium salt of carrageenan was replaced by the sodium salt. This suggests that synergistic interactions are present between the carrageenan and the BSA gel networks, but not between BSA and carrageenan in the sol state.

Distribution and regulation of cyclooxygenase-2 in carrageenan-induced inflammation.

1 We characterized the regulation of cyclooxygenase-2 (COX-2) at the mRNA, protein and mediator level in two rat models of acute inflammation, carrageenan-induced paw oedema and mechanical hyperalgesia. 2 Carrageenan was injected in the hind paw of rat at low (paw oedema) and high doses (hyperalgesia). COX-2 and prostaglandin E2 (PGE2) levels were measured by RT-PCR and immunological assays. We also determined the distribution of COX-2 by immunohistochemistry. 3 The injection of carrageenan produced a significant and parallel induction of both COX-2 and PGE2. This induction was significantly higher in hyperalgesia than in paw oedema. This was probably due to the 9 fold higher concentration of carrageenan used to provoke hyperalgesia. 4 Immunohistochemical examination showed COX-2 immunoreactivity in the epidermis, skeletal muscle and inflammatory cells of rats experiencing hyperalgesia. In paw oedema however, only the epidermis showed positive COX-2 immunoreactivity. 5 Pretreatment with indomethacin completely abolished the induction of COX-2 in paw oedema but not in hyperalgesia. 6 These results suggest that multiple mechanisms regulate COX-2 induction especially in the more severe model. In carrageenan-induced paw oedema, prostanoid production have been linked through the expression of the COX-2 gene which suggest the presence of a positive feedback loop mechanism.

Casein micelle/iota carrageenan interactions in milk: influence of temperature

The behaviour of iota carrageenan/skim milk mixtures was studied at 60°C and on cooling. At 60°C, iota carrageenan flocculates casein micelles by depletion. Comparison of the gelling properties of iota carrageenan in skim milk and permeate during cooling and heating shows that the presence of micelles increases the gelation temperature, the gel rigidity, and the gel melting temperature. These observations lead to the hypothesis that a double network is formed. It is suggested that the first is because of casein micelles bridged by adsorbed carrageenan. This network is responsible for the differences in properties between gels in permeate and skim milk. The second network requires a minimum carrageenan concentration and has properties very similar to those of an iota carrageenan gel in permeate. The apparent micelle size was determined as a function of temperature in milk 100-fold diluted in permeate in the presence of iota carrageenan or guar gum. These measurements confirm the existence of a specific attractive interaction between carrageenan and casein micelles. The interaction seems to require a certain charge density on the polymer. An attractive interaction between casein micelles and iota carrageenan only occurs when the latter is at least partially in the more densely charged helical form.

The influence of locust bean gum and dextran on the gelation of κ-carrageenan

The interaction of κ-carrageenan with locust bean gum and dextran has been studied by rheology, differential scanning calorimetry (DSC), and electron spin resonance spectroscopy (ESR). Rheological measurements show that the carrageenan gel characteristics are greatly enhanced in the presence of locust bean gum but not in the presence of dextran. Carrageenan/locust bean gum mixtures show two peaks in the dsc cooling curves. The higher temperature peak corresponds to the temperature of gelation and its intensity increases at the expense of the lower temperature peak as the proportion of locust bean gum in the mixture increases. Furthermore, the DSC heating curves show enhanced broadening when locust bean gum is present, indicating increased aggregation. These results are taken as evidence of carrageenan/locust bean gum association. The gelation process has also been followed by ESR using spin-labeled carrageenan. On cooling carrageenan solutions, an immobile component appears in the ESR spectra signifying a loss of segmental mobility consistent with chain stiffening due to the coil → helix conformational transition and helix aggregation. For carrageenan/locust bean gum mixtures, carrageenan ordering occurs at temperatures corresponding to the higher temperature DSC setting peak and the temperature of gelation. Similar studies using spin-labeled locust bean gum show that its mobility remains virtually unaffected during the gelation process. It is evident, therefore, that carrageenan and locust bean gum interact only weakly. It is proposed that at low carrageenan concentrations the gel network consists of carrageenan helices cross-linked by locust bean gum chains. At high carrageenan concentrations the network is enhanced by the additional self-aggregation of the “excess” carrageenan molecules. For carrageenan/dextran mixtures, only one peak is observed in the dsc cooling curves. The onset of gelation shifts to higher temperatures only at very high (20%) dextran concentrations and this is attributed to volume exclusion effects. Furthermore, there is no enhanced broadening of the peaks in the DSC heating curves as for the carrageenan/locust bean gum systems. It is therefore concluded that carrageenan/dextran association does not occur. The difference in behavior between locust bean gum and dextran is attributed to the greater flexibility of the dextran chains. © 1996 John Wiley & Sons, Inc.

Characterization of rheological properties of systems containing sugar substitutes and carrageenan

The effects of addition of κ‐carrageenan to solutions containing 40% (w/w) sugar substitute on the rheological properties of these systems were investigated at 25 °C using a rotational viscometer at rotational speeds of 6, 12, 30, and 60 rev min−1. The flow behaviour of the solutions was adequately described by the power law model with or without yield stress. The consistency index (K) and the flow behaviour index (n) were determined from shear stress vs. shear rate data. The flow parameters of the solutions depended on the carrageenan concentration. The apparent viscosities of the systems decreased with increasing shear rate, indicating pseudoplastic behaviour. The final carrageenan concentration was found to be an effective factor controlling the degree of sliminess of the model food systems studied.

Response surface analysis of chlortetracycline and tetracycline production with K-carrageenan immobilized Streptomyces aureofaciens

A full-factorial experimental design at three levels with two independent variables, carrageenan concentration (1.0, 1.5, and 2.0%) and potassium chloride concentration (0.3, 0.7, and 1.1 M) was studied in order to analyze the effect of both factors on the antibiotic production of K-carrageenan-immobilized mycelia of Streptomyces aureofaciens. The response surfaces obtained have indicated that both carrageenan and potassium chloride concentrations have a pronounced effect on the yield of chlortetracycline (CTC) and tetracycline (TC) produced by S. aureofaciens. By exclusively varying the immobilization condition, the tetracycline production can be enhanced more than eight times (12.3 mg g −1 biomass for immobilized cells vs. 1.5 mg g −1 biomass for free cells) in comparison with free-cell mycelial cultures.

SANS contrast in iota-carrageenan gels and solutions in D 2O

SANS of Na +-iota-carrageenan in D 2O/saline solutions was measured as a function of concentration, temperature and type of counterions (K + or Na +). High and low scattering-contrasted gels and solutions were detected. High contrast is caused by aggregation of low-hydrated chains at high concentration of carrageenan in the presence of gel-promoting counterions. The aggregates do not disappear at 60°C, although at this temperature the molecules should partialy lose their ordered conformation. The network formation, observed by SANS, does not happen in high-contrast system immediately after cooling and takes a few hours to be completed at 12°C. The minimum concentration sufficient for the high-contrast regime in 0.1 M KCl lies between 15 and 25 mg/ml.

Milk protein-carrageenan interactions

Factorial experimental designs were employed to study the major factors governing the gelation of milkl κ-carrageenan mixtures. The relative effects of carrageenan concentration, pH, ionic strength, casein proteins, whey proteins and κ-casein genotype on the mechanical properties of the gels were studied using dynamic rheological techniques. Gel transition temperature was governed mainly by ionic strength and carrageenan concentration whilst gel strength was influenced by carrageenan concentration and pH. It was found that the relative importance of the milk proteins to gelation varied with carrageenan concentration. It appeared that at high levels of κ-carrageenan (i.e. 0.1% w/w) gelation was predominately the result of association of κ-carrageenan helices to produce self-supporting gels. Milk proteins appeared to have little effect at high levels of carrageenan. However, milk proteins interfered with gel formation at carrageenan concentrations lower than 0.018% w/w, thus increasing the amount of micellar casein by twofold inhibited gelation. Serum proteins also suppressed gelation, albeit at lower κ-carrageenan concentrations. These results suggested that, in the presence of milk proteins, gel formation involved mainly carrageenan—carrageenan cross-linkages and not carrageenan—casein or casein-casein linkages. Nevertheless, the possibility of a strong interaction between κ-carrageenan and κ-casein on the micelles which has to be satisfied first, leaving insufficient carrageenan to provide network forming capability, cannot be ruled out.

Gelation and flocculation of casein micelle/carrageenan mixtures

The specific attractive interaction between carrageenan and casein micelles is widely exploited in the dairy industry to tailor the texture of dairy desserts. However, in industrial practice it has been observed that the addition of carrageenan can cause casein micelles to sediment rapidly when the mixture is above the gelation temperature. To better understand this undesirable phenomenon, carrageenan/skim milk mixtures have been observed over a wide range of compositions at 65 and 25°C. Interactions occurred for iota, kappa and lambda carrageenan at both temperatures. At 65°C sedimentation was observed when the carrageenan concentration was above 0.2%. At 25°C either phase separation or gelation could occur. Depletion flocculation is suggested as a partial explanation for these observations. The effects of casein micelles on the viscoelastic properties of iota carrageenan have been measured in the absence of flocculation. Their presence decreases carrageenan s gelation concentration and increases both the gelation temperature and the elastic modulus.

Rheological studies of synergistic kappa carrageenan-carob galactomannan gels

The mechanical properties, Young's modulus and yield stress of different carob galactomannan-kappa carrageenan blends have been examined using an Instron testing machine as a function of the following parameters: 1. (1) Constant total polysaccharide concentration. 2. (2) Galactomannan concentration for a given carrageenan concentration. 3. (3) Carrageenan concentration for a given galactomannan concentration. 4. (4) Galactomannan molecular weight. 5. (5) Carrageenan molecular weight. The properties of the binary gels were compared to the kappa carrageenan gels. From the results, two types of gel structure could occur: a coupled network defined by specific junction zones (and involving unsubstituted mannose residues of the galactomannan chains) and also a gel structure with both polysaccharides associating independently.

Characterization of kappa-carrageenan gels used for immobilization of Bacillus firmus.

In this study, aimed at a biochemical and physical characterization of kappa-carrageenan gels used for entrapment of Bacillus firmus NRS 783 (a superior producer of an alkaline protease), effects of carrageenan concentration, gelation temperature, initial cell loading, and strength of the curing agent (KCl) on the properties of cell-free and cell-laden gels were examined. The physical properties of the differently prepared gels that were examined included density, free volume fraction, mechanical strength, and change in gel volume during gel curing. The biochemical characteristics studied included viability of gel-entrapped cells, cell leakage from cell-laden gels, and cell penetration into cell-free gels. For the range of carrageenan contents investigated [between 2% and 5% (w/v)], the mechanical strength of the gels with/without KCl curing was observed to increase with an increase in carrageenan content of gels. The mechanical strength of each gel increased substantially upon extensive curing. Free volume fractions in excess of 0.8 were observed for all gels. Of cells that were viable prior to immobilization, 90-92% remained viable after formation and extensive curing of gels for cell-gel mixtures prepared at 45 degrees C. Attempts at prolonged storage of cell-laden gel beads at 0 degrees C as stock cultures of immobilized B. firmus were unsuccessful due to a significant decline in cell viability during such storage. On the basis of the cell leakage studies, the average pore sizes of 2%, 3%, 4%, and 5% gels were deduced to increase in the following order of carrageenan content (w/v): 4%, 3%, 2%, and 5%. Commensurate with the decrease in the average pore size (or the increased tightness of the gels) with increasing carrageenan content, both the extent of cell leakage and the extent of net cell penetration decreased with increasing carrageenan content for the first three gels. Owing to non-uniform distribution of free space and much larger pores, the extent of net cell penetration in 5% carrageenan gels was considerably low, while the extent of cell leakage in 5% carrageenan gels was an order of magnitude greater than the extents of cell leakage in the other three gels.

The decrease of thaumatin's sweetness intensity upon interaction with carrageenan

Carrageenan was added at various ratios to thaumatin, a sweet protein, and the interactions between thaumatin and λ−, κ− and ι-carrageenan were investigated from the following standpoints: pH, turbidity at 550 nm, CD spectral change (Δ∈) and the decrease in sweetness intensity. Decrease in thaumatin sweetness intensity was observed with lower pH (<4) and higher carrageenan concentrations in the following order: γ− ≒ ι− > κ-carrageenan. There was no correlation between sweetness intensity decrease and turbidity. With the increase in carrageenan concentration, CD spectral change (Δ∈) was distinctly observed at pH 3–4. Thaumatin's sweetness intensity decreased simultaneously.

Effect of Manufacturing Conditions on Rheology of Banana Gelified Milk: Optimization of the Technology

ABSTRACTBanana Gelified Milk (BGM) was processed under four operating conditions: cooking time (15–85 min), cooking temperature (65–95°C), starch concentration (7–11 g.L‐1), and carrageenan concentration (2–6 g.L‐1). Rheological measurements were obtained using a concentric cylinder viscosimeter with shear rate ranging from 5 to 80 sec‐1. The consistency coefficient, the flow behavior index, the apparent viscosity and the yield stress were determined and compared to those of BGM prepared by an industrial process. An experimental design with 24 experiments was used to optimize BGM preparation. Proposed mathematical models showed that the apparent viscosity was mainly affected by carrageenan concentration. However, cooking temperature had greatest effect on yield stress. An optimized product was prepared reducing cooking time and temperature. Carrageenan was optimized to 3.5 g.L‐1. This provided a product with good texture and acceptable taste. This was confirmed by sensory evaluation.

Detection of food gums on polyamide strips using horseradish peroxidase—benzidine staining and laser-beam densitometry

Solutions of food gums were applied to polyamide strips, stained with horseradish peroxidase (EC 1.11.1.7)—benzidine (HRP-B) and scanned with a laser densitometer. The staining technique was effective for anionic gums, including algin, carrageenan, carboxymethylcellulose, gum arabic, pectin, propyleneglycol alginate and xanthan, but ineffective with the neutral gums, guar gum, hydroxypropylmethylcellulose and locust bean gum. Cellulose acetate strips were also examined but were less effective because of high background staining. For carrageenan a band containing 20 ng could be readily detected. Standard curves for carrageenan concentrations from 0.008 to 0.4% were linear, with r > 0.95 for samples run on the same strip. There was substantial variation from strip to strip, but consistent results were obtained when all bands (samples and standards) were on the same strip. Analysis of carrageenan that was added to milk and heated showed recoveries close to 100%.

Carrageenan-stimulated release of arachidonic acid and of lactate dehydrogenase from rat pleural cells

Cells isolated from the rat pleural cavity consist mainly of macrophages, mast cells, eosinophils, and lymphocytes. Isolated pleural cells labeled with [ 14C]arachidonic acid released appreciable amounts (∼12%) of radiolabel upon exposure to pharmacological concentrations of carrageenan (1–100(μg/ml). The release of radiolabel was decreased by an inhibitor of phospholipase A 2 ( p-bromophenacyl bromide) but not by an inhibitor of arachidonate cyclooxygenase (indomethacin). The released products were arachidonic acid and, to a much lesser extent, prostaglandin E 2 and leukotriene C 4. The release of radiolabel was associated with release of cytosolic lactate dehydrogenase over the same range of carrageenan concentrations. Time-course studies indicated that release of radiolabel preceded that of lactate dehydrogenase. Since p-bromophenacyl bromide blocked stimulated release of radiolabel but did not prevent release of lactate dehydrogenase, it is unlikely that increase in arachidonate causes carrageenan-induced cell damage. Nevertheless, the question of whether the activation of phospholipase A 2 in the pleural cells, most probably the macrophages, was sufficient to initiate the carrageenan-induced inflammatory response requires further study. Cytotoxicity which was apparent with as little as 5 μg/ml of carrageenan, may have been a significant consequence of carrageenan action.