122
Spoilage in dried Shrimps
that all transactions in shrimp meat are character-
ized by a desire to dispose of the commodity in
the quickest possible manner and this is mainly
due to the very low keeping value of the product
prepared in the manner described above.
Panikkar's observations on the prawn industry
of the Malabar coast with special reference to
Travancore [1937] have thrown some light on the
bionomics of a few of the species constituting the
fisheries, methods of their capture and preserva-
tion. He has also given a short account of the
history of the industry, in which he has casually
mentioned the handicaps of the present trade
and emphasized the need for improving the
methods of production and preservation on
scientific principles. Referring to the low keeping
value of the cured shrimps, he has remarked that
they remain fit for human consumption only for
about four months and that they are spoiled
afterwards. But he has neither given the factors
leading to the output of such inferior products nor
the cause of the spoilage. Nor has any attempt
hitherto been made for investigating the cause of
spoilage and formulating measures for its pre-
vention.
It is well known that cured shrimps deteriorate
very quickly and that this spoilage
is
mainly due to the attack of minute organisms
mistakenly termed 'lice' by the local fishermen
and merchants. It is estimated that this spoilage
is definitely responsible for the deterioration
of a large proportion of the total
export,
involving considerable loss to the industry.
A study of this spoilage and suggestion of
remedial measures for its prevention are two of the
important and urgent necessities of the shrimp
trade and the present work was undertaken with
this object in view.
METHODS OF INVESTIGATION
For the purpose of investigating the causes of
spoilage commercially cured shrimp and samples
prepared in the laboratory were used. The
laboratory samples were prepared from back-
water specimens belonging to the family Penæidæ.
In curing them in the laboratory, they were boiled
in a small quantity of water for about ten to
fifteen minutes and then dried in the open sun.
The duration of drying was varied from one to
three days in order to obtain samples under
different degrees of desiccation. Thus for
example, certain samples were dried for one day,
others for two days and still others for three days.
Similarly, in order to study the influence of
different concentrations of brine on the spoilage,
samples were treated in brine varying from
2-8 per cent. In all cases the samples were
artificially inoculated with the parasites for
studying the reaction and respective degrees of
resistance.
As dried shrimps are usually sold in the shelled*
and unshelled conditions, both the types of pro-
ducts were prepared and by combining various
factors involved in the methods of preservation,
the following list of samples was obtained.
1a.
1b.
2a.
2b.
3a.
3b.
4a.
4b.
5a.
5b.
6a.
6b.
7a.
7b.
8a.
8b.
9a.
9b.
10a.
10b.
11a.
11b.
Commercially cured shrimps . .
Commercially cured shrimps . .
Lake shrimps dried for one day . .
Lake shrimps dried for one day . .
Lake shrimps dried for two days . .
Lake shrimps dried for two days . .
Lake shrimps dried for three days .
Lake shrimps dried for three days .
Shrimps cured in 2 per cent brine .
Shrimps cured in 2 per cent brine .
Shrimps cured in 3 per cent brine .
Shrimps cured in 3 per cent brine .
Shrimps cured in 4 per cent brine .
Shrimps cured in 4 per cent brine .
Shrimps cured in 5 per cent brine .
Shrimps cured in 5 per cent brine .
Shrimps cured in 6 per cent brine .
Shrimps cured in 6 per cent brine .
Shrimps cured in 7 per cent brine .
Shrimps cured in 7 per cent brine .
Shrimps cured in 8 per cent brine .
Shrimps cured in 8 per cent brine .
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
unshelled
shelled
All the samples were kept in separate containers
and changes in their conditions noted. In ex-
periments of this type, where reaction of various
methods of preservation to attack of the para-
sites is to be studied, it is necessary to keep all
samples under almost identical conditions and this
was achieved by using uniform grade of shrimps
and containers and maintaining uniform tem-
perature. By adopting these methods, sources
and chances of infection were rendered constant
as far as possible, so that whatever differences are
noticed with regard to the time taken for the
infection to set in, they are to be attributed to the
resisting properties of the respective samples.
The history of each sample was carefully
studied and recorded in a tabular form (Appendix
II).
Infected samples and freshly cured ones were
placed side by side in separate containers and the
fresh lot watched for probable sources of infection.
Appendages of possible transmitting agents of
the vicinity such as ants and flies were also
examined under a microscope.
Reaction of the attacking organisms to condi-
tions of humidity was also investigated by keeping
the infected shrimps in desiccators from which
moisture had previously been removed by means
of anhydrous calcium chloride.
SPOILAGE
The onset of spoilage in shrimps is generally
marked by the gradual change in the colouration
*Samples in which the shells have been removed