RADIATION NOVEL METHOD FOR THE FABRICATION OF GELATINCARRAGEENAN COMPLEXES

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RADIATION NOVEL METHOD FOR THE FABRICATION OF
GELATIN-CARRAGEENAN COMPLEXES
F.F.VIEIRA A.J.ALISTE N.L. DEL MASTRO
Radiation Technology Center, Nuclear and Energy
Research Institute (IPEN-CNEN/SP), Travessa R,
400 Cidade Universitaria, São Paulo, SP - BRAZIL
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INTRODUCTION
The complementary application of both chemical
and biochemical synthetic methods provides access
to a diverse array of biopolymers. There is a
oontinuing nned to modify the porperties of these
materials for enhanced and novel applications.
Properties of these complexes or blends strongly
depend on the components and parameters of
preparation. In the synthetic plymer area an
established approach for modifying material
characteristics is to make use of polymer blends.
Less frequently there is an attractive
interaction between chemically dissimilar polymer
providing single-phase materials.
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OBJECTIVE
This article presents the preliminary results of
a novel method for the fabrication of biopolymer
complexes using edible polymers. The
polysaccharide chosen for the study was
carrageenan and gelatin was taken as the proteic
component of the possible complex because its
gelation and water holding abilities. Instead of
using electrochemical synthesis as was described
recently we applied ionizing radiation to induce
complex formation.
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CURRENT RADIATION PROCESSING APPLICATIONS A)
RADIATION STERILIZATION OF MEDICAL DEVICES AND
DISPOSABLES B) FOOD IRRADIATION C) POLYMER
MODIFICATION. Safety evaluation of plastic
packaging materials for use in food irradiation.
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FOOD IRRADIATION

• Ingredients to be used for food processing
  should be decontaminated in order to prevent food
  spoilage and food-borne diseases. Irradiation
  with ionizing radiation is one of the most
  effective means to sanitize dry food ingredients.
  Also, radiation processing is increasingly
  applied to shelf-stable, ready-to-eat meals. Only
  certain radiation sources can be used in food
  irradiation
• Radionuclides (60Co or 137Cs)
• X-ray machines with maximum energy of 5 MeV
• Electron beams with maximum energy of 10 MeV.

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MATERIAL AND METHODS
Materials Five grams cellophane packaged samples
of commercial edible bovine powder gelatin was
employed (1). Commercial carrageenan samples
(Carragel NM Adicon) were employed. Adequate
solutions of both substances (1 gelatin and 1.5
carrageenan) were prepared by dissolution in hot
(80?C) water according our previous experiences.

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IRRADIATION
Gelatin and carrageenan solutions alone as well
as ternary water-gelatin-carrageenan systems
(97.51.01.5) were 60Co-irradiated with
different radiation doses 0 1 2.5 5 and 10kGy
by means of a Gammacell 220 (AECL), dose rate 7.3
kGy/h.
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VISCOSIMETRY The radiation effects were
measured following viscosity changes at 50?C
using a Brookfield viscometer model DVIII,
spindle SC4-18, with Rheocalc software. Viscosity
measurements were performed according to our
previous experience and the results are the mean
of at least 3 experiments.
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RESULTS
Figures 1a and 1b present viscosity values versus
dose of irradiated 1 gelatin solutions measure
just after irradiation and 24h later
respectively. It is possible to see an increase
in the viscosity values with the increasing
applied dose for dose values starting at 2.5kGy.
It was no statistically difference in both sets
of readings, showing no further reaction during
the first day after irradiation. In previous work
we had shown that when gelatin was irradiated as
a powder, a decrease in the viscosity of the
solutions prepared afterward was obtained as the
dose increased. In the present case, there was a
viscosity increase for higher dose indicating a
radiation polymerization, e.g. production of
collagen like structures. A six times increase in
the viscosity of the 10 kGy irradiated solution
when compared with the unirradiated samples was
obtained.
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Fig.1a - Gelatin just after irradiation
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Fig. 1b Gelatin 24 h after irradiation
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RESULTS (cont.)
Figures 2a and 2b show the viscosity changes
performed by the carrageenan solution when
irradiated with different radiation doses. A
notorious reduction of viscosity was obtained
with increasing dose being the viscosity reduced
by about 77 with the maximum dose applied, 10
kGy. Like other polysaccharides, carrageenan
displayed a similar rheological behavior after
irradiation whether irradiated as a powder or in
aqueous solution 6. It seems that
radiation-induced degradation occurred in both
cases and was the predominant phenomenon.
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Fig. 2a. Carrageenan just after irradiation
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Fig.2b. Carrageenan 24 h after irradiation
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RESULTS (cont.)
Figure 3a and 3b presents the results of the
irradiation of the ternary water-gelatin-carrageen
an systems (97.51.01.5). The viscosity
variation of the irradiated ternary system did no
correspond to neither of the component alone nor
to the sum of both of them.
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Fig.3a. Carrageenan Gelatin just after
irradiation
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Fig. 3b. Carrageenan Gelatin 24 h after
irradiation
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DISCUSSION
From the standpoint of food irradiation, the most
important changes in polysaccharides caused by
irradiation is the breaking of the glycosidic
bond, which results in the formation of smaller
carbohydrate units, and chain-type reactions.
Radiolytic products like acids, keto acids and
aldehydes could be found. On the other hand,
higher molecular weight derivatives are also
formed.
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DISCUSSION (cont.)
Although a mutual protection is exerted when
different substances are irradiated together, the
different viscosity versus dose patterns obtained
supports that a new complex has been formed and a
different balance among radiation degradation and
radiation polymerization phenomena prevailed.
These preliminary results will be confirmed by
diverse composition of the ternary system as well
as further calorimetry, thermogravimetry,
infra-red spectroscopy, mechanical properties and
sample composition analyses for different
intervals after irradiation.
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ACKNOWLEDGEMENTS
The authors would like to thank the Brazilian
Research Council (CNPq) and Sao Paulo State
Research Support Foundation (FAPESP) for support
of this research.