THE ANNALS OF ‘’VALAHIA’’ UNIVERSITY OF TÂRGOVIŞTE
Fascicle VIII
2007
STRUCTURE AND PROPERTIES OF CARRAGENAN
Corina Popescu*, Maria Iordan*, Boscornea Cristian**
*Valahia University of Tărgovişte, Faculty of Environment Engineering and Biotehnologies, Departament of Food
Products Engineering, Street Unirii, No. 18-24, Romania
E-mail: corinapopescu2003@yahoo.com
** Politehnica University of Bucuresti
Abstract
Carrageenans are used in a wide range of industries, especially the food industry, where their gelling
qualities and viscointensifying properties are greatly valued. The structure of Carrageenans has a major role when
it comes to characteristics and properties. Kappa and Iota Carrageenans have very similar structures and therefore
share many properties. These polymers have a backbone of galactose but differ in the proportion and location of
ester sulfate groups and the proportion of 3,6-anhydrogalactose. Kappa carrageenan is able to interact synergistically
with other gums, such as locust bean gum and konjac mannan, to modify further the gel texture.
Keywords: carrageenan, solubility, gelation, synergism
structural function of foods is known as
functional property, and it is expressed among
others as gelation capacity, viscosity
modification, and stabilization of suspensions,
emulsification, and abillity to retain water
(Medina-Torres, et al. [3]).
Alginate, carrageenans, xanthan gum, locust
bean gum, cellulose derivatives, starches and
pectins are some of the exemples of
hydrocolloids that have been studied in low-fat
meat products (Candogan and Kolsarici [1]).
Carrageenan is a generic term for a group of
commercially important galactan sulpfates
extracted from red seaweed. Red algae are
phylogenetically the oldest division of marine
macrophytes. They differ very much in
polysachharide composition from all the other
plants and usually contain sulfated galactans as
the main structual mateirial of cell walls and
intercellular
matrix.
Some
of
these
polysaccharides
known
as
agars
or
carrageenans have valuable gelling and
stabilizing properties and are prepared from
algae industrially on a large scale as
phycocolloids of great practical importance.
Many others have no gelling properties, but are
very promising, biologically active compounds.
The evidence on the structure of these
polysaccharides may be used to corrrelate the
structural details with physico-chemical
properties
or
biological
activity.
Polysaccharide-chemical may also supplement
classical criteria, such as morphology, anatomy
and life history studies, in the elucidation of
INTRODUCTION
In recent years, many consumers have limited
their dietary intake of fat and calories due to
diet and health concerns. Consumer interest in
reducing dietary fat and calorie intake has
encouraged meat technologists to develop lowfat meat product formulations having good
economical value and desirable palatibility.
Substuting water for fat in low-fat processed
meat products improves sensory and texture
characteristics wheres it leads to increased
cooking loss and purge. Because of the fact that
water addition alone could not provide all
quality characteristics to the final product, the
focus has been directed to the use of texturemodifying ingredients having good water
binding ability. Among these, hidrocolloids
with their unique characteristics in building
texture, stability and emulsification are of great
interest in low-fat proceseed meat area due to
their ability of binding water and forming gels
(Candogen and Kolsarici [1].
Foods are multicomponent in nature and many
of their functonal characteristics depend on
their macromolecular composition. Because of
this active role, macromolecules in foods have
been studied as individual species or
interacting with the surroundings. In many
cases, the macromolecules responsible for the
mechanical and physicochemical properties of
many food systems are polysaccharides
(hydrocolloids). The ability that these
macromolecules possess in binding part of the
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2007
intensive as the seaweed is collected by raking
or hand-gathering, mechanical harvesters have
been tested but have shown little to no
improvement in yield. The seaweed is then
washed to remove sand, stones and other
impurities. Then the seaweed is taken to the
production plant and extracted under alkaline
conditions to produce quality carrageenans.
This lasts several hours at temperatures close to
the boiling point of the alkaline solution. The
extract is then filtered and concentrated to a
final carrageenan concentration of 3%. It is
then precipitated by the addition of 2propanol, dried, and ground to the desired
particle size. Often additives are blended into
the final product, such as sucrose and glucose,
to increase viscosity or gelling properties. The
major device that affects the gelling properties
of the final carrageenan product is alkali used
and time of extraction used (Lamond [9]).
taxonomic position of several red algae (Usov
[6]).
Carrageeenans are extensively, gel or texture
enhancers, stabilisers, etc. These additives give
textural properties and protective effects to a
wide range of products such as frozen desserts,
chocolate, cottage chesse, whipped cream,
instant breakfasts, yoghurt, jellies, pet foods,
relishes, sauces and syrups (Tojo end Prado
[5]).
Source. The term “carrageenan ” describes a
class of sulphated galactan poliyaccharides
that occur as cell wall constituents in numerous
species of red seaweed (marine algae of the
class Condrus crispus found on the coasts of
Irland, England and Spain, Eucheuma species
near
the
Philippines,
Rhodophyceae)
(carbohidrates [10]).
k-Carrageenan is predominantly obtained by
extraction of the tropicalseaweed Kappaphycus
alvarezii, known in trade as Eucheuma cottonii
(or simply cottonii). Eucheuma denticulatum
(trade name Eucheuma spinosum or simply
spinosum) is the main species for the
production of ι-carrageenan. λ-Carrageenan is
obtained from diffrent species from the
Gigartina and Chondrus genera. The
sporophytic plants of these seaweeds produce
λ-carrageenan whereas the gametophytic plants
produce a k/ι-hibrid type of carrageenan. These
k/ι-hibridcarrageenans consist of a mixed chani
containing both k-and ι-units and range from
almost pure ι-carrageenan to almost pure kcarrageenan. The production of λ-carrageenan
implies the selection of samples in the
sporophyte stage while the extraction can be
carried out with hot water as the cyclization, in
alkaline medium,. to θ-carrageenan is difficult
and this product has essentially the same
properties as λ-carrageenan (F.van de Velde, et
al. [2]).
Structures. Structure of carrageenans are a
family of water soluble, linear, sulfated
galactans. The backbone of the polysaccharide
is formed of D-galactose units linked
alternately with α-(1-3) anb β- (1-4) linkages.
The carrageenans are clasified according to the
presence of 3,6-anhidro-D-galactose on the 1,4linked residue and the position and number of
sulpfated groups (fig. 1). Greek letters have
been assigned to varions ”idealised”
disaccharide repeating unites. However, natural
carrageenans containining only one type of
repeating disaccharide may not exist but
consist of molecular hybrids of two or more
idealised structures. The properties of such
hybrids depend very much on the distribution
of the different disaccharide unites along the
polymeric chain.
The
three principal types of industrial
importance are kappa, iota and lambda
carrageenans. Kappa (k) and iota (i) forms are
gelling polymers, white lambda (λ) is a nongelling, thickening agent (Tojo and Prado [5]).
Manufacturin. There are many different
methods used to extract Carrageenans from
seaweed and processing conditions are usually
considered trade secrets by the manufactures as
these produce the variables in the Carrageenan
properties. Firstly the Carrageenan-containing
seaweeds are harvested which is labour
Solubility. All carrageenan are soluble in hot
water. Sodium salts of both kappa and iota
carrageenans are soluble in cold water.
potassium and calcium salts do not dissolve;
however, they exhibit the ability to swell.
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Swelling is variable and is dependent upon the
particle density. iota carrageenan is sensitive to
calcium ions and it will swell to form
thixotropy results from the formation of
bivalent calcium bridges between the swollen
particles to form a losse 3- Dimensional
network (Budnis [7]).
The influence of temperature is an important
factor in deciding which carrageenan should be
used in a food system. All carrageenans
hydrate at high temperatures and kappa and
iota carrageenans in particular exhibit a low
fluid viscosity. On cooling, these carrageenans
set between 40–60ºC, depending on the cations
present, to form a range of gel textures (Imeson
[8]).
double helices then must aggregate to form a 3dimensional network. A general mechanism of
gelation is shown in Figure 2. The mechanism
indicates that both kappa and iota gels are
thermoreversible gels. The gels will become
fluid when heated above their melting
temperature and will reset upon cooling with
minimal to no loss of their original gel strength
(Budnis [7]).
The gelation mechanism is controversial, and
the domain model has been suggested to
explain gelation in terms of coil-to helix
transition followed by aggregation of domains
of double helices in the presence of gelinducing ions. The i-carrageenan displays a
greater hydrophilic character than the kcarrageenan because of the presence of
additional sulphate grout in the anhydrons
galactose residue. This also enhances its ability
to inhibit syneresis, even though its gels are
less rigid than those of k-carrageenan owing to
its lower aggregation capacity (Medina-Torres
[3]).
Figure 2.Thermoreversibility of
Carrageenan gels (Lamond, 2004)
Figure 1. Structures of kappa, lambda and
iota carrageenan
Hot solutions of kappa and iota carrageenans
set to form a range of gel textures when cooled
to between 40 and 60ºC depending on the
cations present. Carrageenan gels are thermally
reversible and exhibit hysteresis or a difference
between setting and melting temperatures.
These gels are stable at room temperature but
can be remelted by heating to 5–20ºC above
Carrageenan gelation mechanism. Kappa and
iota are gelling carrageenans. In order for
gelation to occur, the helix of a single
carrageenan molecule must come in close
proximity to a second identical single
carrageenan helix to form a duble helix. The
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2007
and types of carrageenan suitable to such food
applications (Budnis [7]).
the gelling temperature. On cooling the system
will re-gel.
The ionic composition of a food system is
important for effective utilisation of the
carrageenan. For example, kappa carrageenan
selects for potassium ions to stabilise the
junction zones within the characteristically
firm, brittle gel as shown in Fig. 3 (a). Iota
carrageenan selects for calcium ions to bridge
between adjacent chains to give typically soft
elastic gels in Fig. 3(b).
The presence of these ions also has a dramatic
effect on the hydration temperature of the
carrageenan and on its subsequent setting and
remelting temperatures. For example, iota
carrageenan will hydrate at ambient
temperature in water but the addition of salt
raises the gel point so that the solution is
converted into a gel with distinct yield point
which is used for cold-prepared salad
dressings. Sodium salts of kappa carrageenan
will hydrate at 40ºC but the same carrageenan
in a meat brine will only show full hydration at
55ºC or above. Gelation of kappa and iota
carrageenans with cations (fig. 3).
As a carrageenan dispersion is heated there is
no significant particle swelling or hydration
until the temperature exceeds about 40–60ºC.
As the particles hydrate the viscosity rises as
the swollen particles offer more resistance to
flow. Further heating to 75–80ºC produces a
drop in viscosity. On cooling, the solution
shows a marked increase in viscosity followed
by gelation below temperatures of 40–50ºC.
The hydration and gelation temperatures are
strongly dependent on the salts associated with
the carrageenan or added separately to the
solution. For example, levels above about 4%
sodium chloride can prevent full hydration of
carrageenan in meat products. In contrast, the
very dilute levels of around 200ppm of
carrageenan used to stabilise chocolate milks
and other dairy beverages may not form a
stabilising gel network until the temperature
drops below 20ºC. The presence of high solids,
such as in confectionery, effectively
concentrates the carrageenan and cations on the
aqueous phase so the gelation may occur at 80–
85ºC or higher placing limitations on the levels
Synergism whith other gums. Kappa
carrageenan is synergistic with locust bean
gum and konjak mannan. Hot solutions of
kappa carrageenn-locust bean gum strong
elastic gels with low syneresis when cooled
below 50-600C. Locust bean gum is a
galactomannan with a level of substitution of
one part mannose to four units of galactose.
However, this substitution is not regular and
regions of the locust bean gum are
unsubstituted. The mannose-free regions of the
locust bean gum are able to associate whith the
repeating helicalstructure of regions of the
locust bean gum are able to associate with the
repeating helical structure of carrageenan
dimers to form gels. The maximum interaction
and hence pik rupture gel strongth, occurs at a
rations betwen 60:40 and 40:60 kappa
carrageenan to locust bean gum. These polymer
combinations are used in very large quantities
in cooked meats and in gelled petfoods
(Imeson [8]).
These synergistic interactions enhance the gel
strength and water binding capabilities, as well
as modify the gel texture to be more elastic and
resilient (Budnis ).
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2007
with characteristic structural elements can be
obtained in reasonable high quantities. On the
other hand molecules enriched with uncommon
irregularities or non carrageenan constituents
might be retained and subsequently isolated by
a proper fragtionation technique (see below). In
this way, cryptic structures, that otherwise
would be masked below the noise level in the
13
C-NMR spectra can be identified.
Carrageenases
are
endo-β-galactanases,
cleaving the internal β-(1→4) linkages with
sulfate substitution pattern related specificity.
Oligosaccharides of the neocarrabiose are the
main products from molecules or molecular
regions that possess structurall regularities of a
certain length. By far the most popular enzyme
is k-carrageenase, which might be obteained
from several bacteria. it has successfully ben
produced in a stable form by large-scale
fermentation of Pseudomonas carragenovora
on k-carrageenan from Kappaphycus alvarezii.
In general it has been quie well established
among researchers that stable enzyme have
successfully been prepared by cloning in E.
coli, giving more stable enzymes, especially
important for ι-carrageenanse. Unfortunately at
the
moment
carrageenases
are
not
commercially available for routine structure
analysis (F. van de Velde, et al. [2]).
a) Mechanism gelation of K-carrageenan
b) Mechanism gelation of iota-carrageenan
Figure 3. Gelation of kappa and iota
carrageenans with cations (Budnis [7])
Protein Reactivity. All carrageenans are known
to be protein reactive. Reactivity is a function
of the isoelectric point (pI) of protein, the pH
of system, the weight ratio protein to
carrageenan, the type of protein, and the
molecular weight. The interaction between
proteins and carrageenan occur by a
combination of twe mechanisms. The
mechanisms are divalent bridging and ionic
bonding. Above the pI of the protein, the
carboxylic acid groups of the protein will be
ionized; therefore, the carrageenan does not
interact with the protein due to negativenegative repulsions (Budnis [7]).
REFERENCES
Journals:
[1]
[2]
Enzymatic
depolymerisation.
As
for
polysaccharides in general, the use of specific
enzymes is an ultimate tool for structural
analysis of carrageenans. By selecting a
suitable enzyme, well-defined oligosaccharides
[3]
31
Candogean, K. and Kolsarici, N. The
effects of carrageenan and pectin on some
quality characteristics of low-fat beef
frankfurters. Meat Schience 2003, 64,
199-206.
F. van de Velde, Knutsen, S. h., Usov,
A.I., Rollema, H.S. and Cerezo, A.S. 1H
13
and
C
high
resolution
NHR
spectroscopy
of
carrageenans:
application in reserch and
industry.
Food Schience & Technoligy 2002, 13,
73-92.
Medina-Torres, L., Brito-De La Fuente,
E., Torrestiana- Sanchez, B., Alonso, S.
Mechanical properties of gels formed by
THE ANNALS OF ‘’VALAHIA’’ UNIVERSITY OF TÂRGOVIŞTE
Fascicle VIII
2007
[4]
[5]
[6]
mixtures of mucilage gum (Opuntia ficus
indica) and carrageenans. Carbohydrate
Polymer 2003, 52, 143-150.
Tojo, E. and Prado, J. Chemical
composition of carrageenan blends
determined
by
IR
spectroscopy
combined with a PLS multivariate
calibration
method.
Carbohydrate
Reserch 2003, 00, 1-4.
Tojo, E. and Prado, J. A simple 1H NMR
method for the quantification of
carrageenans in blend. Carbohydrate
Polymers, 2003, 1-5.
Usov, A.I. Structural analysis of red
seaweed galactans
of
agar
and
carrageenan groups. Food Hydrocolloids,
1998, 12, 301-308.
Books:
[7]
Budnis,
W.
Carrageenan.
FMC
BioPolymer, 2000,
section 13, 1-34.
[8] Imeson,
A.P.
Carrageenan. FMC
Corporation (UK) Ltd, 5, 88-102.
[9] Lamond, T., Characterization of Seaweed
derived
carrageenans. CHEE 4006,
2004., 1-55.
Refernces sourrced via the worldwidw web:
[10] www.carbohidrates.htm
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