Public health and carrageenan regulation: a review and analysis

The status of carrageenan in the regulatory sphere influences how and where it may be used, with implications for seaweed farmers, carrageenan manufacturers and consumers. Over the period 1935 to the present the status of carrageenan has been effected by changes in the regulatory environment that reflect new understandings about carrageenan, health and health risks as well as broader trade, social and political changes. This paper reviews regulatory progress from the 1930s to the present. It reflects, in particular, the shifting priorities in public health and their effects on the regulatory status of carrageenan. Four case studies of public controversies about carrageenan safety are discussed in relation to regulatory responses and their public health significance. It is concluded that current assessments of risk associated with carrageenan have, in some contexts, failed to take into account the full spectrum of safety assessments that have been carried out and the maturing of food additive regulations thereby allowing a myth of risk to continue.     

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.     

Hypotensive and edematogenic effects of carrageenan in the irradiated rat]

Iota carrageenan induces the same hypotensive effect in leucopenic and thrombopenic rats as in normal animals. This hypotensive activity depends on kininogen-kinins activation. In the irradiated rats, the inflammatory response to iota carrageenan is reduced. The blood cells are thus responsible of the major part of the late inflammatory effect. There is non parallelism between this hypotensive and the oedematogen activities of iota carrageenan in the rat.     

Recent developments in manufacturing and marketing carrageenan

Carrageenan has annual sales of over US$ 200 million, about 15% of the world use of food hydrocolloids. The market for carrageenan has grown exponentially at 5% per year for at least 25 years: 5 500 metric tons in 1970, and over 20 000 metric tons expected in 1995. The industry has become dominated by very large, multi-product companies with carrageenan factories in Europe and the US, but factories are now springing up in the Philippines and Chile, where red seaweeds grow in abundance. About 80 000 tons of dry red seaweeds are needed to produce 20 000 tons of carrageenan. About 40 000 tons comes from the Philippines, 15 000 tons from Indonesia, 15 000 tons from Chile, and 10 000 tons from elsewhere. Carrageenan growth depends on food fads like the McLean hamburger and food winners like processed pork and turkey. Carrageenan is a regulated food additive, and current health concerns focus on the minimum safe molecular weight for carrageenan when eaten. The most innovative development in carrageenans in recent years has been the introduction of a food grade version of lower cost natural grade carrageenan. Its acceptance, however, has been hampered by strong resistance from conventional carrageenan producers.     

Chemical and physical characteristics of carrageenan extracted from Eucheuma spinosum harvested from three different Indonesian coastal sea regions

Carrageenan extracted from Eucheuma spinosum harvested from three different coastal sea regions, where this alga has been mainly cultivated, were determined for their chemical and physical characteristics. The carrageenan was extracted from the seaweed using hot alkali followed by precipitation, drying, and milling. The carrageenan properties were determined in terms of yield, ash, mineral, sulfate content, functional group, molecular weight, and viscosity profile. Physical characteristics of carrageenan were evaluated by a texture analyzer for gel strength and a rapid visco analyzer for viscosity. The yield of carrageenan from Sumenep (34.81 ± 5.83%) and Takalar (37.16 ± 3.26%) was found to be relatively higher than that of Nusa Penida (25.81 ± 1.93%). The calcium content was higher than magnesium, potassium and sodium content, and no cadmium, lead, mercury, and arsenic detected in all carrageenan. The ash content was around 29%; while, the sulfate content was in the range of 30–32%, and those were not different in all carrageenan. The presence of sulfate content was identified by FTIR at absorption band of 1373 cm^?1. It was found that the molecular weight of carrageenan from Takalar were relatively higher and the gel strength of carrageenan from Takalar were significantly higher than that of carrageenan from Nusa Penida and Sumenep. Likewise, upon cooling from 80 to 20°C, the viscosity profile of carrageenan from Takalar characterized by higher viscosity compared to that of carrageenan from Sumenep and Nusa Penida. These results indicated that carrageenan from Nusa Penida, Sumenep, and Takalar were identified as iota‐carrageenan with similar physico‐chemical characteristics except for the gel strength, viscosity profile upon cooling from 80 to 20°C and the yield.     

Composition of carrageenan blends inferred from C-NMR and infrared spectroscopic analysis

Carrageenan blends mainly composed of kappa, iota and lambda carrageenan were investigated by ¹³C-NMR and infrared (IR) spectroscopy. ¹³C-NMR was shown to be a powerful tool for quantifying the kappa-iota ratio in a carrageenan blend. The technique, however, was not helpful for identifying lambda carrageenan. Consequently, IR spectroscopy was used to achieve a semi-quantitative determination of lambda carrageenan. By combining both techniques, the carrageenan composition of several commercial samples was established.     

Inhibition of carrageenan edema by carrageenan itself]

The influence of two kinin forming agents: iota carrageenan and ellagic acid, on the paw oedema induced by 48/80, an amino-liberator, or by carrageenan iota, has been studied, in the Rat. Ellagic acid and carrageenan, by intraperitoneal injection, reduce the paw oedema induced respectively by 48/80 and carrageenan itself. This inhibition depends on a non-specific "counter-irritation" and not on kininogen stores depletion. Ellagic acid, by intravenous injection, diminishes the oedema induced by carrageenan; swelling due to 48/80, is not affected. So kininogen activation plays some role in the inflammatory processes induced by iota carrageenan. Carrageenan by intravenous injection, suppresses his own inflammatory action but does not influence at all the similar action of 48/80. The anti-inflammatory effect of carrageenan does not exclusively depend on kininogen stores depletion.     

Molecular and rheological characterization of carrageenan solutions extracted from Kappaphycus alvarezii

This study evaluates and relates the molecular and rheological characteristics of native carrageenan obtained from Kappaphycus alvarezii seaweed. Native carrageenan was extracted by a differentiated methodology by atomization drying process, which reduces the time for obtaining carrageenan dry powder and minimizes costs and environmental damages. Rheological properties of native carrageenan were compared with a commercial carrageenan grade. Molecular properties were performed by SAXS and GPC analysis and the rheological properties by DMTA and stress relaxation tests. Molecular analysis proved a folded and compact molecular structure and indicated the presence of chains with different molecular weights for native carrageenan. The results obtained showed that the helix-coil transition occurs at temperature about 50°C. The native and commercial grade carrageenan presented the characteristic of viscoelastic materials and their gel properties show a higher contribution from solid elastic component, and the initial force (F(0)) was higher in commercial carrageenan than native one.     

Effects of alginates and sodium carrageenates mixed with soy proteins on the coefficient of protein efficiency

Male 21 d-old Wistar rats, were fed for 4 wk with diets containing casein or soybean proteins (10%) with 0.5, 1, 2 or 3% sodium alginate or sodium carrageenan or without any alginate or carrageenan. Daily protein intake and weight gain of casein-fed rats were not significantly different (P less than 0.05) from those of rats fed soybean meal with alginate, whatever the dose received. Rats fed 3% carrageenan in soybean meal had significantly higher feed intake than that of rats fed casein. At the levels studied, alginate had no effect on the Protein Efficiency Ratio (PER), but carrageenan did. The addition of increased quantities of carrageenan to soybean meal followed by heating the mixture led to a progressive and significant decrease in PER at all levels of carrageenan compared to casein feeding. The addition of 3% carrageenan to heated soybean meal, corresponding to 0.62% of meal diet, led to a significant decrease in PER. These results confirm the precipitating role of carrageenans on proteins.     

Tensile and Tear Strength of Carrageenan Film from Philippine <Emphasis Type="Italic">Eucheuma</Emphasis> Species

The tensile and tear strength of carrageenan film from Philippines Eucheuma species were investigated using NEC tensilon universal-testing machine according to American Society for Testing Materials methods. These properties are important for assessing carrageenan film as packaging material. The and types were used in the study. The effect of glycerine on the tensile and tear strength including elongation was also evaluated. Addition of glycerine tended to lower the tensile strength of the film and increase its elongation properties including the tear strength. Carrageenan film without glycerine was much stronger. Glycerine made the film more flexible and easy to deform. The composite film of carrageenan and konjac gum did not exhibit elongation. It also showed higher tensile strength than did the composite film of carrageenan and xanthan gum. Compared with -type carrageenan film, -type carrageenan film without glycerine was more comparable to low-density polyethylene (LDPE) film in terms of tensile strength as was the composite film of carrageenan–konjac gum. The -type carrageenan film with glycerine was more comparable to LDPE film in terms of tear strength. The elongation reading for carrageenan film was lower than that for LDPE film. Morphologic studies showed that the carrageenan film had sets of pores distributed randomly at different places as compared to LDPE film. It also showed that the carrageenan film was more fibrous than LDPE film.     

Reduction of nitro-substituted 1,2-dihydro-3H-1,4-benzodiazepine- 2-ones by E. coli cells immobilized in carrageenan

Reduction of nitro-substituted 1,2-dihydro-3H-1,3-benzodiazepine-2-ones by E. coli cells immobilized in carrageenan was studied. The corresponding amines are the sole products with a 100% yield as compared to the native cells. Conditions for immobilization of E. coli cells in the home-produced carrageenan was worked out: the cell to carrageenan ratio is 1:10 (w/w), granulation in toluene at 0-(+)4 degrees, treatment with 0.3-0.4 M KCl. The carrageenan-immobilized cells are stable upon storage, repeated usage (after 10 cycles about 80% of the initial activity is retained), and when being used in column fermenters.     

Identification of carrageenan in mammalian tissues: An analytical and histochemical study

Synopsis Methods have been developed for the analytical estimation and histochemical demonstration of carrageeman in the granuloma induced in rats and guinea-pigs by subcutaneous injection of degraded carrageenan.The analytical method for the determination of carrageenan in tissues involved a preliminary clean-up procedure. The tissues were defatted by solvent extraction and incubated with papain and trypsin to remove proteins. Carrageenan and naturally occurring acid mucopolysaccharides were isolated using cetyl pyridinium chloride. The subsequent separation and estimation of carrageenan was carried out by electrophoresis on cellulose acetate paper. Following electrophoresis the cellulose acetate strips were incubated with hyaluronidase to remove acid mucopolysaccharides, and stained with Toluidine Blue. The stained band corresponding to pure degraded carrageenan was quantitated on a scanning densitometer. The method was capable of detecting 0.25 g of degraded carrageenan in tissue.The most suitable method for the histochemical demonstration of carrageenan in paraffin embedded tissues was found to be Alcian Blue at either pH 1 or a CEC (critical electrolyte concentration) of 1.0 M MgCl₂ (pH 5.8). At this pH or CEC, both the carrageenan and the strongly acidic glycosaminoglycans were stained. Prior digestion with hyaluronidase and neuraminidase eliminated the staining of the tissue polysaccharides so that the carrageenan could be visualized within macrophages and in the extracellular space. Mast cell granules retained their staining properties after mucolytic digestion; but morphologically, mast cells could be distinguished from macrophages containing carrageenan.     

Spatial and temporal variations of Chondrus crispus (Gigartinaceae, Rhodophyta) carrageenan content in natural populations from Galicia (NW Spain)

Qualitative and quantitative differences in carrageenan composition of gametophytes and tetrasporophytes of Chondrus crispus were observed in this study. Carrageenans in gametophytes belong to the kappa family (κ-, ι-, ν- and μ-carrageenan). The dominant fractions were κ- and ι-carrageenan (more than 50% of the total carrageenans). In tetrasporophytes, the presence of λ-carrageenan was confirmed. Carrageenan content in gametophytes (37.4?±?1.68% DW) was higher than in tetrasporophytes (29.13?±?0.76% DW). Spatial and temporal variation in carrageenan content in both life cycle phases appears to be related mainly to seawater and air temperatures, insolation, water movement and desiccation. The highest values of carrageenan content were recorded in those localities where higher values of precipitation, wind speed or water movement occurred. A bimodal temporal pattern on carrageenan content was observed. Fronds showed a high carrageenan content in spring and autumn. During these seasons, the content was over 40% in gametophytes and 30% in the tetrasporophytes. In summer and winter, these values down in both life cycle phases below 30%. In general the highest carrageenan contents were related to highest seawater temperatures. On the contrary, high air temperature and high insolation appeared to be unfavourable for carrageenan production. GLM models were obtained to predict carrageenan production from natural C. crispus populations, along Galician coast.     

Cation specificity of the order—disorder transition in iota carrageenan: effects of kappa carrageenan impurities

The temperature dependence of the optical rotation of carrageenan segments (iota, kappa and iota/kappa mixtures) in different salt solutions (tetramethylammonium or potassium chloride) has been studied. In solutions of pure iota carrageenan (90% iota structure) no evidence of any pronounced cation specificity nor of any thermal hysteresis in the iota carrageenan order-disorder transition was found. However, mixtures of iota and kappa carrageenan displayed a cation specificity similar to that previously observed in iota samples of lesser chemical purity, indicating that kappa impurities in iota samples may be located in regular sequences, rather than randomly in the carrageenan primary structure. Our findings strongly suggest that the order-disorder transitions of iota and kappa sequences in mixed samples occur independently.     

Interaction of polymorphonuclear leukocytes, bradykinin and carragenin. Transference reaction in the rat

1. Injected in the paw of the rat, polymorphonuclear leucocytes do not increase the oedematogen action of bradykinin, but increase the action of lambda carrageenan. 2. This potentiation of carrageenan action is not modified when PG biosynthesis in leucocytes is inhibited by indomethacin or aspirin. It does not appear in rats previously treated by indomethacin or aspirin. 3. Our results suggest that rat polymorphonuclear leucocytes increase the inflammatory reaction, when they are stimulated by carrageenan, by the release of a phospholipase A2 activity which induces PG biosynthesis in rat paw tissues.     

Computer modelling of kappa carrageenam-mannan interactions

Molecular modelling has been used as a theoretical approach to investigate the kappa carrageenan structure and its interaction with mannan chains. Calculations revealed the existence of six minima for the kappa carrageenan structure in solution. Two of them were very close to the structure found in the solid state. The methodology allowed the calculation of the theoretical counterpart of the structures based on x-ray fibre diffractions studies. In the second step of this study, we have shown that there is the possibility of interactions between kappa carrageenan double helices and mannan chains. This interacting process is allowed by the flexibility of the mannan chains and structural changes of the kappa carrageenan double helices. The calculations suggest that the disaccaride mannan fragment might be required for recognition. The result of our investigation are in good agreement with a model of gel structure based on experimental data. This approach could be applied to simulate and predict other associations in molecular assemblies.     

The carrageenan controversy

Except for Japanese nori, the production of seaweed hydrocolloids consumes the largest amount of macroalgae annually, and carrageenan is the largest consumer of this group. However, carrageenan has run into rough water with food processors and consumers, especially those who read ingredient labels. Carrageenan is being singled out on the Internet as being unsafe for human consumption, even though it is approved for food use by all major food regulatory agencies worldwide. Most recently, it has been approved for use in liquid infant formula, a particularly sensitive application when it comes to food safety. How did this negative attitude toward carrageenan evolve? It can be traced to a research group at the University of Illinois who claim that carrageenan upregulates inflammatory genes of the intestinal epithelium. There is no evidence that this in vitro model applies in vivo and a growing body of research is showing it does not. Nevertheless, it was picked up by various bloggers feeding on contradictory issues and quickly went viral. This paper describes the evolution of the “carrageenan controversy” and provides information for food producers and consumers on new more robust studies confirming that it is safe to consume foods containing carrageenan. This article also presents actions being taken by carrageenan producers and users, to reduce the noise in the public domain from the controversy.     

Analysis of the conformational properties of κ‐ and ι‐carrageenan by size‐exclusion chromatography combined with low‐angle laser light scattering

The conformational properties of κ‐carrageenan in 0.2M LiI and ι‐carrageenan in 0.2M LiCl were analyzed by size exclusion chromatography combined with low‐angle laser light scattering. Fractionated samples with narrow molecular weight distributions (M_w/M_n ∼ 1.4) were used, and M_w in the disordered states were 35,000 (κ‐35) and 200,000 (κ‐200) for κ‐carrageenan and 65,000 (ι‐65) and 170,000 (ι‐170) for ι‐carrageenan, respectively. The analyses were performed across a temperature range where the conformational transitions occurred, and at extremely low concentrations (2–50 μg/mL) due to low amounts of samples injected and the subsequent dilution occurring during the separation. The results indicate that a twofold increase of the molecular weight (M_w) occurs for κ‐carrageenan upon inducing the ordered conformation. For ι‐carrageenan an additional increase in M_w may take place, which is attributed to the strong tendency for aggregation of ordered chains especially at high molecular weights. The results thus suggest that both κ‐ and ι‐carrageenan are double (or multiple) stranded in their ordered conformations, within the concentration range studied here. © 1999 John Wiley & Sons, Inc. Biopoly 49: 71–80, 1999     

Nociceptor functions in intact skin and in neurogenic or non-neurogenic inflammation

Acute neurogenic or non-neurogenic inflammation was elicited in skin patches innervated by the saphenous nerve of anaesthetized Sprague Dawley rats. Lambda carrageenan was used to induce non-neurogenic inflammation, mustard oil (allyl-iso-thio-cyanate) or antidromic nerve stimulation to induce neurogenic inflammation. Antidromic nerve stimulation yielded plasma extravasation but no significant sensitization of unmyelinated nociceptor units. In contrast, mustard oil and carrageenan yielded plasma extravasation and sensitization of nociceptors, though carrageenan sensitized only part of them. Sensitization resulted in ongoing spike discharges and in a shift of response curves to lower temperatures when controlled radiant heat stimuli were applied to the receptive fields. Responses to mechanical stimuli with v. FREY hairs were not significantly altered. Effects of neurogenic and non-neurogenic inflammation on unmyelinated nociceptor units are compared.     

Cellulose/carrageenan/TiO<Subscript>2</Subscript> nanocomposite for adsorption and photodegradation of cationic dye

Cellulose/carrageenan/TiO₂ nanocomposites were simply prepared by the co-dissolution of cellulose and carrageenan, and the dispersion of TiO₂ in 1-ethyl-3- methylimidazolium acetate, followed by reconstitution with anti-solvents. The cellulose/carrageenan/TiO₂ composite showed a much higher adsorption capacity for methylene blue (MB) than the cellulose and cellulose/TiO₂ composite. The cellulose/carrageenan/TiO₂ composite also degraded MB more efficiently in aqueous solution than the cellulose/ TiO₂ composite. The MB adsorption capacity of the cellulose/carrageenan/TiO₂ composite increased linearly with increasing carrageenan content in the composites.