Wonder guard
M Shobita Rao, SR Kanatt, Dr Ramesh Chander and Dr Arun
Sharma explain what makes radiation processed chitosan a
novel food preservative
Chitosan is the second most abundant
natural biopolymer on earth.
Chitosan, the deacetylated, non-toxic
derivative of chitin is a copolymer of ß-(1, 4)-
2-acetamido-2-deoxy-D-glucose and ß-(1, 4)-
2-amino-2-deoxy-D-glucose units (Figure 1)
and a naturally occurring component in shells
of crustaceans and cell walls of fungi.
Crustacean waste contains 14 to 35 per
cent of chitosan on a dry weight basis and
seafood processing industries generate more
than 1.2 x 105 metric tonnes of such waste
annually. Chitosan, though being abundant
and having numerous applications, has yet to
find utilisation on large scale because of its
limited solubility in water. Chitosan is soluble
in certain acid solutions, such as formic acid,
acetic acid and lactic acid. When dissolved in
acid solution, chitosan becomes polycationic
polymer, which possesses many functional
properties in food applications. These
applications include anti-microbial effect,
intestinal lipid binding and serum cholesterol
lowering effects, water binding ability, antioxidative
and preservative abilities in muscle
foods and emulsifying capacity.
Radiation processed chitosan
Chitosan has many applications in food
processing and preservation owing to its
diverse properties. However, its low solubility
at neutral pH, high viscosity and high
molecular weight limits its use in various
applications. Therefore, methods are being
developed to prepare low molecular weight
chitooligosaccharides with novel functions.
Several enzymic and chemical methods for
producing chitosan oligomers have been
described. The chemical methods include acid
hydrolysis with either cold nitrous acid or hot
hydrochloric acid; both of these methods
involve rather long and harsh treatments.
Enzymes from a variety of sources have also
been used for producing chitooligosaccharides.
Chitosan degrading enzymes can be isolated
from vegetable sources, bacteria and
actinomycetes. Chitooligosaccharides obtained
by chemical treatments and enzymatic means
have been reported to possess better
properties than the native chitosan. It is well
known that polysaccharides such as cellulose
can be degraded due to scission of glycosidic
bonds by radiation. Gamma radiation has
been reported to degrade chitosan into
oligomers depending on dose.
We, at the Food Technology Division,
BARC, have investigated the efficacy of
gamma radiation in preparation of such
chitooligosaccharides. It was observed that
irradiation leads to formation of
chitooligosaccharides with reduced viscosity
and enhanced antioxidant activity. Radiation
processed chitosan is a novel food preservative
as it is endowed with anti-microbial, antioxidative,
water binding abilities and
emulsifying capacity.
....C
O N T D
TO
READ FURTHER... SUBSCRIBE TO YOUR
COPY TODAY!!!
