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DEPARTMENT OF FISHERI ES AND THE ENVI RONMENT
(\
TECHNOLOGY BRANCH
HALIFAX, NOVA SCOTIA
E.G.
BLIGH, DIRECTOR
OCTOBER 1977
NEW SERIES CIRCULAR NO. 65
MECHANICAL REr10VAL AND DETERMINATION OF COD
(PHOCANEMA DECIPIENS) FROM FISH FLESH
WOR~1
- J.C.C. WANG AND S. VARGA -
o
Cod taken from the Gulf of St. Lawrence and it's proximity is often heavily
infested with parasite (codworm).
The candling technique used by fish processing
plants to remove parasites from fillets is frequently unsuccessful and uneconomic.
Separation of parasites from fish flesh by the meat/bone separator and strainer had
been found successful.
All but a few small (0.1 cm) fragments of cod worm were
removed from the meat.
The number of parasites and parasite fragments in unstrained minced
fish flesh can be numerous.
These fragments are difficult to count by candling.
enzymatic method of worm separation greatly facilitates this task.
digested with a solution made up from 0.85% HCl and 0.6% pepsin.
The flesh is
This solution
selectively digest fish protein but not the parasite and its fragments.
(
parasites then can be detected and counted on fine mesh screen.
An
The undigested
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Introduction
The infestation of fish flesh with worms is unsightly and many consumers
find their presence objectionable.
Some species of fish such as cod from different fishing grounds vary
greatly in the extent to which they are infested with worms.
infestation takes place as follows:
The
the adult parasite lives in the stom-
ach of both the common seal and the grey seal, and fertilized eggs are passed
into the sea with the excreta.
The egg hatches to give a microscopic
worm which can survive in the sea for a week or two, but must be swallowed
by small shrimp-like animal or small fish if the life cycle is to be continued.
Cod becomes infested by eating the shrimp-like organism or small
fish containing the worm.
The parasite burrows through the stomach wall
of the cod and becomes encased either in the liver around the gut or penetrate
in the flesh when infestation is heavy.
Cod worms in the fillet often
become coiled like the spring of a watch and remain encased in a tough bag
produced by the fish tissues.
eats the infested cod.
The life cycle is completed when a seal
Since seals act as hosts to the worms at one stage
in the life cycle, the degree of infestation in cod thus depends upon the
number of seals in the fishing ground.
The most severe infestation in
the Canadian Atlantic Coast occurs in the Gulf of St. Lawrence and off the
Southwestern tip of Newfoundland and off Cape Breton Island.
cod
t~~eu f~vm
Fillets of
these areas may have a mean infestation rate of 17 parasite
per 10 Ibs. (Varga and Anderson, 1971).
There is considerable information pertaining to a disease syndrome of
the infestation of fish by cod worm (Cheng, 1976).
However, little is known
3
about the parasitic symptoms in humans.
It is speculated that since the
parasite is pathogenic to their intermediate hosts, it may also be pathogenic
to human hosts.
An acute abdominal syndrome in humans caused by the infes-
tation of anaselis nematodes, which are similar to cod worms, has been
reported in Holland (Kuipers, et ale 1960, and Van Thiel et aI, 1960).
Anaselis infections are mainly derived from the digestion of raw or poorly
cooked marine fish.
However, the worms are generally killed by ordinary
cooking procedures and by freezing.
The fish processing industry attempts to remove the cod worms from the
fish flesh by picking them as they pass over a candling table, but this
deworming process is not completely successful, especially when the flesh
is heavily infested.
Excessively infested fillets are often processed into
fish meal since the deworming would be too costly and often unsatisfactory.
o
The possible removal of worms from infested fish with a mechanical
deboner and strainer was examined in our laboratory.
The results have
shown that the efficiency of deworming can be 100% on whole worms and as
high as 90% on worm fragments.
The dewormed minced flesh could be used for
the production of fish cakes and/or other formulated foods.
Materials and Methods
Fillets infested with 10 worms/lb. were put through a Bibun meat separator
(type SDX 16).
respectively.
The holes on the separator drum were either 5.0 or 3.5 rom
The separated meat was then fed into a Bibun meat strainer
(type MS-25) which had either 2.0, 1.6 or 1.2 rom holes on its drum.
Worms infestation rates on the fillets were estimated by candling, while
the number of whole worms and worm fragments in the minced flesh as well as
4
in the refuse were determined by pepsin digestion method (anonymous).
This
o
digestion procedure consisted of mixing 1 part of minced fish with 10 parts
of enzyme solution (0.6% pepsin in 0.85% HCl) and incubation of the mixture
at 37 C for 8 hours or longer.
During incubation the mixture was shaken
occasionally and when the digestion of flesh was completed, the mixture
was filtered through a fine sieve screen (mesh size: no. 100 Tyler standard).
Material retained by the screen was washed several times with water and the
whole worms and fragments were counted.
Results and Discussions
The separation efficiency of cod worms by the meat/bone separator having
two different drum sizes is illustrated in Table 1.
The efficiency of the
meat strainer with three different screens is shown in Table 2.
As it can
be seen, the meat/bone separator removes only a small percentage of the worms
from the flesh.
Most of the worms remain intact in the products.
The
straining, on the other hand, is very effective in removing whole worms and
even small worm fragments from the minced meat.
The strainer with drum
having 1.2 rom holes removes practically 100% of cod worms and fragments larger
than 0.1 cm.
Thus the process consisting of meat/bone separation followed
by straining is highly successful in deworming infested flesh which otherwise
may be processed into fish meal rather than food.
The pepsin digestion method is well suited to determine worm and/or bone
count in fish flesh, either minced for filleted.
n
5
Acknowledgement
The authors wish to thank Mr. W.J. Brownlee, Chief, Maritime Inspection
Service District No.2, for supplying the infested cod fillets.
References
Anonymous.
The digestion of fish flesh by pepsin solution.
Cheng, T.C., 1976.
The natural history of anisakiasis in animals.
J. Milk
Food Technol. 39: 32.
Kuipers, F.C., P.H. Van Thiedl, W. Rodenburg, W.J. Wielinga, and R.T.
Roskam. 1960.
a worm.
o
Eosinophilic phlegmon of the alimentary canal caused by
Lancet pp. 1171-1173.
Van Thiel, P.H., F.C. Kuipers and R.T. Roskam.
1960.
A nematode parasitic
to herring, causing acute abdominal syndromes in man.
Trop. Geogr.
Med. 2: 97.
Varga, S., and W.E. Anderson.
1971.
Parasite infestation of cod fillets
before and after candling in the Maritimes Area, Internal Technical
Report, Inspection Branch, Fisheries and Marine Service, Environment
Canada.
April 1971.
pp. 12.
c
Table 1.
Separation of parasites from cod fillets by a
Bibun meat/bone separator.
Hole diameter on
separator drum
%
parasites in
refuse
% parasites in
minced flesh
(rom)
0
3.S
10-lS
8S-90
S.O
3-S
9S-97
Table 2.
Separation of parasites and fragments from minced cod flesh by a Bibun meat/bone
strainer.
Hole diameter
on strainer
drum (mm)
c
Number of intact
codworms
Refuse
Minced/
strained
flesh
Number of codworm
fra~ents
Minced/
strained
flesh
Refuse
Size of codworm
fragments (cm)
Minced/ Refuse
strained
flesh
Percentage
separation
efficiency
of
fragments
2.0
None
66
553
68
0.2-0.5
0.5-1. 8
11%
1.6
None
99
147
44
0.1-0.2
0.5-1.0
23%
1.2
None
102
9
80
0.1
0.5-1.0
90%
o.
o