J. Biol. Macromol., 5(3), 47-52 (2005) Gelation and gel properties of polysaccharides gellan gum and tamarind xyloglucan
Department of Food and Nutrition, Faculty of Human Life Science, Osaka City Univeristy,
3-3-138, Sumiyoshi-ku, Sugimoto, Osaka City, Osaka, 558-8585, Japan
Received September 5, 2005, accepted September 14, 2005 Keywords: Gel, Gelation, texture modifier, gellan, xyloglucan, rheology, DSC
Polysaccharide is used widely in food, cosmetic and pharmaceutical industries. The main use is to give appropriate texture to the products. Thus the polysaccharides used in such way are called texture modifier. Here two important texture modifiers, gellan and tamarind xyloglucan are introduced. The former one is a microbial polysaccharide with gelling ability. Gelling ability makes gellan valuable since only a few polysaccharides can form a gel. Most polysaccharides do not form a gel by themselves; however, some can form a gel under appropriate conditions. The latter one is a plant polysaccharide which forms a gel under appropriate conditions. Gelation and gel properties of gellan and tamarind xyloglucan are described.
suspension . The polysaccharides used
in these ways are called texture modifier and
enhance the quality of product by thickening
creation of various kinds of texture modifier
and gelling, and by reducing the undesired
defect of water release (syneresis) in some
products, and by stabilizing emulsion and
Gelling ability is an important property as
a texture modifier and some polysaccharides
can form a gel at low concentrations (~1%).
There are only a few polysaccharides which
have a gelling ability by themselves at low
Life and Environment, Nara Women’s University, Kitauoya Nishi Machi, Nara
concentration whereas a lot of non-gelling
polysaccharides are used as a thickener and
calorimetry (DSC), epigallocatechin gallate
In the present article, recent insight about
the gelation and gel properties of gellan gum and tamarind xyloglucan shall be
described. Gellan gum is a polysaccharide
1,4-β-D-glucuronic acid, 1,4-β-D-glucose,
which can form a gel at low concentrations.
Gelation mechanism and gel properties of
O’Neil et al. and Jannson et al. [3, 4].
gellan have not been clarified well at the
Gellan gels in the presence of appropriate
amount of cations are transparent, resistant
polysaccharide obtained from tamarind seed,
to heat in the wide range of pH . Brittle
is a valuable thickener and stabilizer. We
suitable for gel products with new texture.
particle, called a microgel, has a specific
gelling conditions of tamarind xyloglucan
texture like fluid gel which was produced
gellan gels, gelation and gel properties have
fundamental questions still remain to be
polysaccharide produced by micro-organism
previously known as Pseudomonas elodea.
properties of gellan gum, a collaborative
research group was organized conjunction
quality. The primary structure of gellan
gum is composed of a linear tetrasaccharide
affiliated to the Society of Polymer Science,
Fig. 1. (a) The storage Young’s modulus and (b) the circular dichroism spectra of 1 wt % K-gellan gels affected by the immersion in NaCl solutions or distilled water.
used to study its properties with various
dramatically under gel state at a certain
techniques. The results of the collaborative
studies were published in special issues of
Food Hydrocolloids 7, 361-456 in 1993,
differential scanning calorimetry (DSC) and
Carbohydrate Polymers 20, 75-207 in 1996,
and Progress in Colloid and Polymer Science, 114, 1-131 in 1999. Light
helix-coil transition of gellan; thus, we
concluded that a helix-coil transition can
from two single chains to one double helix
occur even in gel state. Since gellan is a
polyelectrolyte, gel properties are influenced
helix to two single chains on heating [7, 8].
gel formation occurs after the coil-to-helix
modulus of the gel increased and circular
dichroism spectra changed as shown in Fig.1.
This was also attributed to the helix-coil
gelation mechanism is described in those
Gel properties also remain to be clarified.
We found that rheological properties change
Fig. 2. The appearance of 1 wt % tamarind xyloglucan in the presence of epigallocatechin gallate (EGCG).
polysaccharide in the primary cell walls of
two-dimensional nuclear Overhauser effect
obtained from the endosperm of the seed of
the tamarind tree, Tamarindus indica, a
member of the evergreen family, that is one
mixtures of polysaccharides can form a gel
of the most important and common trees of
India, Bangladesh, Myanmar, Sri Lanka, and
prepared in order to test whether or not the
Malaysia . Purified, refined tamarind
mixture shows a specific interaction leading
to a synergistic gelation. From viscoelastic
permitted as a thickening, stabilizing, and
mixture formed a gel under the condition
where individual polysaccharide does not
(1→4)-β-D-glucan backbone that is partially
concentrations, indicating the synergistic
measurements, the gelation was detected as
xylose residues are β-D-galactosylated at
a peak that appeared at higher temperatures
than a peak arising from helix-coil transition
Although tamarind xyloglucan itself does
of gellan alone . It was also detected
not form a gel, gel can be obtained under
as a change in circular dichroism which was
appropriate conditions, such as by adding
not observed in tamarind xyloglucan alone
some substances or removing substituents.
xyloglucan and gellan might associate to
galactose residues from tamarind xyloglucan
[14, 15]. In order to seek novel gelling
Recent findings about gellan and tamarind
xyloglucan are the helix-coil transition of
prepared a mixture of tamarind xyloglucan
gellan in gels, the gelation of tamarind
xyloglucan by addition of epigallocatechin
gallate, and the synergistic gelation of a
mixture formed a translucent or opaque gel
mixture of tamarind xyloglucan and gellan.
(Fig.2) . Rheological and DSC studies
It should be noted that it is rare for the
showed that the gelation occurred on cooling
and gel melted on subsequent heating .
leading to gel formation. It is also notable
that only a few mixtures of polysaccharides
xyloglucan chains for a gel network, which
findings are expected to contribute to not
polysaccharides but also create new texture
modifiers suitable for social requirement.
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