第 39 回日本バイオレオロジー学会年会

プログラム・抄録集

STUDY ON GELATION MECHANISM OF MIXTURE SOLUTION OF KAPPA AND
IOTA CARRAGEENANS BY MULTIPLE PARTICLE TRACKING METHOD
1

L. Geonzon1,F. Descallar1, R. Bacabac2, 〇S. Matsukawa1
Department of Food Science and technology, Tokyo University of Marine Science and Technology,
4-5-7, Konan, Minato-ku, Tokyo, Japan 108-8477
2
Medical Biophysics Group, Department of Physics, University of San Carlos, Cebu, Philippines

1. Introduction
Carrageenans are p extracted from species of redseaweeds, and are commonly used as gelling or stabilizing
agent. A generally accepted model of the gelling processof carrageenan solutions involves a coil-to-helix transition
followedbyaggregation

ofhelicesforming

aspace-spanning network[1]. Commonly used gelling
carrageenans are Kappa (KC) and Iota (IC) types. Several
studies shows that mixed KC/IC systems undergo two-stepgelation where two independent gel networks are formed
and a possible phase separation takes place in the mixed
system[2]. This study focuses on the gelation mechanismof KC, IC, and Mixed KC/IC carrageenans throughobservation of the microscopic rheology.
2. TheoryThe mean-squared displacement (MSD) of a particle byBrownian motion is proportional to the diffusion time ina homogeneous media. But in an inhomogeneous media
with tortuous passway for the diffusion, the particle may
exhibit subdiffusive motion as described by the following
equation [3](1)MSD  4 D n
where D corresponds to the diffusion coefficient and n is
the diffusive exponent which is related with the tortuosityof diffusion pass in the inhomogeneous media, 0 < n < 1.
3. Methodology
Sodium-type KC and IC were supplied by MRCPolysaccharide Co. with further dialysis. Solutions addedwith polystyrene beads and 10Mm KCl were stirred for
30 min at 90°C and the final concentration is 2%.
Carrageenan solutions kept at high temperature wereviewed using a 100x/1.30 Nikon oil-type objective withstage controlled using a Peltier thermo 0.68 ° C/min
controller with a cooling rate of. 15-20 particles weretracked using a 1.3M CCD camera and images were
processed using a free software ImageJ. The particles
MSD were calculated using a written Mathematica. Whenthe plots of MSDs showed a monodispersity, averaged
MSD was calculated and fitted on equation (1) to give Dand n for each temperature. When the MSDs showed abimodal dispersity, the MSDs were divided into twogroups to give two averaged MSDs and the fitting gave

two sets of fitting parameters of D and n. The fitting werecarried out on the data of τ=1-10s.
4．Results and Summary
From Figure 1a, IC and mixed KC/IC shows awider variance as gelation proceeds. Both figures at lowtemperatures, MSDs for particles in the mixture could be
divided into two groups to give different Ds and ns asshown two points connected with thin lines. This can berelated to a possibility of the phase separation withdifferent rheological properties. It is found that thedisplacements of embedded particles in the IC gelsdemonstrated higher diffusivity compared to that of KCgels while mixed system appears to have the lowest
diffusivity as this reflects the expected rheology. It ishypothesized that with decreasing temperature, particle
diffusion is inhibited due to the corresponding polymer
network stiffening. Thus, our observed differences inprobe diffusion behaviour
can be associated todifferences in the gelling mechanisms between thecarrageenan isoforms.

Fig. 1. Temperature dependences of D (a) and n (b). Connected squares
refers to a separation of D and n of mixture at low temperature

References[1] L. Du, T. Brenner, J. Xie, S. Matsukawa, (2016) A
study on phase separation behavior in kappa/iota
carrageenan mixtures by micro DSC, rheologicalmeasurements and simulating water and cations migration
between phases, Food Hydrocolloids, 55, 81-88.
[2] T. Brenner, R. Tuvikene, A. Parker, S. Matsukawa, K.
Nishinari, (2014) Rheology and structure of mixed
kappa-carrageenan/iota-carrageenan
gels,Food
Hydrocolloids, 39,272-279.
[3] M.L. Gardel, M.T. Valentine, D.A. Weitz,
Microrheology.Microscale Diagnostic Techniques. K.
Breuer (ed) Springer Verlag (2005)