Annual Report of The Atlantic Fisheries Experimental Station to The

DFO - L brarV I MPO - Bibliothèque
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12069715
CONFIDENT IAL
ANNUAL REPORT
of
THE ATLANTIC FISHERIES EXPERIMENTAL STATION
THE FISBERIES RESEARCH BOARD OF CANADA
1941
Aîlpendices
Page No
Canning Fish
Salt Fish
Fresh Fish Preservation
Cod Liver Oil
Smoked Fish
List of Publications
1
14
36
58
67
69
- 13
- 35
- 57
-.66
- 68
, 70
REPORT OF
THE ATLANTIC FISÉERIES EXPERIMENTAL STATION
HALIFAX, N. S.
for 1941
By S. A. Beatty, Director.
For the past three or four years the staff of the
Atlantic Fisheries Experimental Station has been reduced
considerably below the normal level.
In fact, during a con-
siderable part of 1940, the research staff of the Station
consisted of two senior and two junior workers, During the
latter part of the year the staff was increased by the addition
of Dr. W. J. Dyer and Dr. A. J. Wood.
From January to May we
were without the services of Dr. D. B. Cooper, but at the end
of that period his duties were assumed by Dr. E. P. Linton, who,
because of his previous knowledge of the work, was able very
rapidly to take it over and to pursue it aggressively. During
the year of 1940 Mr. G. J. Sigurdsson joined our staff as a
voluntary worker to investigate problems of bacterial metabolism,
On the completion of his studies for the degree of Master of
Science this spring, he was taken on as a temporary assistant.
Dr. Hess finished his work undor the Lobster Controller in
September of this year, and under an arrangement between
the Lobster Controller and the Fisheries Research Board his
two assistants Mr. A. Hollett and Mr. R. E. S. Homans were
assigned to problems concernitg the canning of lobster, in
our laboratory.
These staff increaseS are reflected in a much
greater output of werk and while a large part of our staff
is still unfamiiiar w ith the practical aspects of the industry,
a considerable part of our work of the present year is capable
of commercial utilization and some of it has already been made
use of,
In spite of our increased personnel the number of
problems is not much larger than last year.
The choice of
new problems was determined by the needs of the country and
Empire in the prosecution of the war y the needs of the industry
itself, the basic work essential to studies of practical nature
and the training and capabilities of our personnel.
Hence
emphasis was placed on urgent problems that appear to permit
of rapid solution,
This is not considered a wise permanent
policy, but the rapid changes in the industry and the pressing
needs resulting from the war outweigh the desire for a long
range policy that might ; after some years, show greater
progress.
The advice of members of the Executive was made
available through visits by the Chairman and the Secretary of
the Board.
While the Subexecutive met only once during the
year, the work of the Station has been kept before the Chairman
as frequently as possible.
5
The results of the More important studies are
given by the researchers themselves in the Appendix to this
Report.
The following summary shows the coordination of the
work, and the possible and actual industrial applications.
Canned fish
Under the Canned Lobster Controller, Dr. Hess has
had two years' experience in the grading of canned lobster.
This work has shown the need of a system of inspection based
in part at least, on objective standards.
The development
of suitable standards is a very difficult task, and within
the time available only a start has been made.
It has been
shown that the Armstrong penetrometer, which has been used to
advantage in the inspection of canned salmon, gives a reliable
measure of the texture of the meat.
It was demonstrated also
that the salt content of the pickle can be determined rapidly
and with sufficient accuracy by direct titration of the diluted
pickle.
The colour of the canned meat is a very important
factor in the de -tDrmination of the value.
No mea, have been
devised to assay this factor accurately because of the colour
characteristics,
It has been found that the pigments can be
extracted and matched against arbitrary colour standards.
This method will probably never be used in routine work, but it
may provide a means of checking grading officials, or of settling disputes between graders and owners.
The development of
such standards is almost essential to the proper grading of the
lobster pack.
This work should be prosecuted as vigourously
4
as possible if greater emphasis is to be placed on the
grading of canned lobster.
Several questions have been raised by the work of
Departmental officials in connection with the lobster
industry, and as many of these have been answered as time
permitted.,.
The enforcement of size limits in the canning areas
has made it necessary to determine the change of body length
as a result of boiling.. It has been shown Uhat lobsters of
minimum legal size do not shrink more than one eighth inches
and hence that lobsters less than six and three eighth inches
in length after boiling,were captured illegally..
A serious error in the determination of drained
.weight of canned lobster has been shown;, that the drained
weight, as determined at presànt, is dependent to a very large
extent on the temperature of the canned moat, and that it is
possible under present practice to obtain differences from
cans, identical except for storage temperature, of as much as
three quarter ounces.
It is suggested that not only the time
of drainage but also the temperature of the product at the
time of examination be fixed.
The occurrence of magnesium ammonium phosphate has
received special attention..
These crystals do not form under
all conditions, and it would appear that if the conditions
resulting in their formation were known the fault would be
5
eliminated entirely,
The phosphate content of the muscle
stays constant throughout the whole moulting period but that
of the blood undergoes wide fluctuation being highest juot
before moulting.
One might infer that the stage of
moulting might be a factor in the formation of the crystalm,
but calculated from the solubility of magnesium ammonium
phosphate in water at the hydrogen-ion concentration of the
can contents, there is always sufficient phosphate to
produce a growth of the crystals.
Analyses for magnesium
show much smaller concentrations.
At present it would
appear that sea water or impure salts may be the source of
the magnesium in the crystals.
The study is being continued
and the role of magnesium should be determined shortly.
If
sea water or impure salts are proven the source of this magnesium, it should be possible to eliminate this defect.
Experimental packs of canned lobster designed to
show the effect on the finished product of; over cooking, overprocessing, the inclusion of weak, soft-shelled, or dead
lobsters, have been made.
These will be examined at intervals
and the results will be made available at the completion of
the work .
The problem of transportation of fish to England,
without low temperatures, of a quality and at a price the
British people are willing to pay, has received considerable
attention,
Experiments with a more palatable dried fish than
6
that produced at the present time will receive attention in
a later section of this Report.
The utilization of our
numerous canneries might provide larger volumes of canned
fish.
Because the British market prefers the Icelandic
type of pack, it was deemed wise to gain some experience with
it,
Successful packs were made and we are now in a position
to supply necessary information to any interested parties.
For the same reason experimental packages of dried
fish and dried vegetables for fish cakes were made.
The
feasibility of putting up such a product has been shown, but
it still remains to be seen whether or not the industry as now'
equipped can dry either in salt fish dryers or fish meal plants,
a fish product equal in quality to that produced on a laboratory
scale, or whether our finished product is acceptable to British
consumers,
Salt fish production
When the work on the production of salt fish was, undertaken some three years ago,
drying of the product.
the first problem attacked was the
It was realized that a study of salting
should precede that of drying, but pressure from the trade
itself, and a lack of suitably trained researchers dictated our
course.
With the addition of Dr, Dyer to our staff it has been
possible to start the work on salting,
The first problem attacked was to _determine the
factors influencing the penetration of salt and the withdrawal
of water under conditions similar to those obtaining in the
7
trade itself.
The rates of salt penetration and moisture
removal, and the effect of some of the factors influencing
these rates are given in Appendix No. 41
The work has gone
almost as far as is advisable at this time. During the coming
year, the effect of the ions ordinarily contaminating fishery
salts will be determined,
In the Annual Report for l93,8, Appendix No , 2, Dr.
Hess reported that the growth of certain halophiles is more
rapid in the presence of high concentrations of solar salts
than in the presence of equal concentrations of chemically pure
salts.
It has been found that the difference in the growth
rate is also very striking at lower concentrations of salt,
solar salts permitting the most rapid growth, chemically pure
salt the least, and the effect of mined salts about half way
between the other two
The studies of the rate of salt penetration offer a
plausible explanation of the occurrence of putty fish.
Large
cod fish have been subjected to conditions similar to those
under which the "putty! forms in the trade.
It has been found
that this type of spoilage is the result of holding the fish at
high temperatures for a time sufficient to allow bacterial penetration into the deep tissues, and salting at a temperature
sufficiently high to allow these bacteria to decay an area in
the centre before the salt reaches that area in a concentration
high enough to stop their action.
•
8
During the past summer, the temperatures were sufficiently low that practically no puttied fish was produced.
A careful survey is being made for the occurrence of these
fish in packages being
ë ut
for boneless, As the fish are
cut, the buyers inform the Station, the proportion of
putty$
the producer, and the time of purchased
a6Curate
We have had
alb temperature records for a typical putty producing area for
the summer of
1940.
The Director has already discussed reme-
dial measures with the majority of the important producers and
will attempt to visit all of them before next June.
Those
interviewed have expressed a willingness to co-operate with
us, in an endeavour to eliminate these losses, or to reduce
them to a negligible amount, We expect that even with
normal
temperatures next year, the amount of putty fish will be small.
One year's successful operation should be sufficient to finish
the problem in so far as the Station is concerned.
A start has been made towards the development of a
salt fish, sufficiently low in salt to be acceptable to the
British market,
and sufficiently dried to stand transshipment
without refrigeration,
The preliminary work gives every indi-
cation that a product only slightly inferior to fresh fish can
be produced.
Present equipment plus additions for brining
could produce dried fillets equivalent to about
2,5,000,000
pounds round fish annually and at a cost lower than bacon.
There would be a saving of about
80
per cent of the original
9
weight of the fish, and the finished product is almost 40
per cent protein.
The work is being prosecuted as rapidly
as possible,
The work on drying of hard salted fish has been
practically finished except for the effect of humidity of
the air.
The data shown in Appendix No. 10, gs well as
previous data show that an efficient dryer should operate in
two stages, the rapid removal of water until the surface
effect makes rapid air flow no longer of advantage, and the
removal of the rest of the water in a dryer of low air
volocity and large capacity,
This work has been seriously interrupted by the
application of the results to commercial practice and by staff
changes.
It is hoped that it can proceed without further
interruption to its completion, probably three months hence.
The study of the drying characteristics of fish of lower salt
content should be much more rapid, as the major difficulties
have been overcome, and the limits can be narrowed more rapidly.
The dataon air temperatures and humidities d our
coast has been supplemented through the co-operation of the
Department of Transport, Eastern Air Command, Halifax.
1
We
obtained in all continuous readings throughout the summer from
nine stations covering all the Maritimes as far north as
Caraquet,
These results have not been worked up and cannot be
worked up by our present staff without thestoppage of work
10
urgently needed, .
It is hoped that assistance can be
obtained to put at least a minimum of these results in an
available form during the present fiscal year.
Fresh fish preservation
For the past year little was done on studies on the
bacterial decomposition of fresh fish because of our reduced
staff.
The work was resumed this year and is making progress.
Previous work was done on gross samples with the flora picked
up by the fish during processing
.
The present attack was made
by studying the action of bacteria, one strain of organism at
a time, on simple media, using the resting cell technique.
The degradation of glucose has been studied quite intensively
and lactic acid is now under investigation.
Glucose has been
broken down to lactic acid, acetic acid, and formic acid,
ethyl alcohol, carbon dioxide and
=e—methyl carIiiol.
The
type of breakdown is influenced by the hydrogen-ion concentration, more lactic acid being produced in acid reaction.
results suggest that the sugar is first broken into two
of three carbons each,
The
»tee&eideA
omo
Because of its slow rate of breakdown
lactic acid is probably not one of these.
The breakdown of
lactic acid itself may throw further light on this type of fermentation,
Some years ago, the quality of the fish in the retail
stores in Toronto,
poor.
Gbviously
Mlntreal
and Halifax was found to be very
either radical changes in the processing of
11
freezlng of the
the fish, or thc%fish are necessary to bOlig the qlality
up to a minimum level.
As a result of the action of the
Department of Pensions and National Health in enforcing the
Pure Food Laws with respect to preservatives, the quality
has fallen off.
The producers are endeavouring to increase
the sales of properly frozen fish but the prospect of disposal
of the major part of cod and haddock fillets in the frozen
state is not bright.
Therefore any enhancement of keeping
time must be brought about by (1) reducing the bacterial contamination, (2) speeding up the time between capture and
final disposal, (3) maintaining minimum temperatures,
But
in spite of all reasonable care in handling it is felt that
the trade c annot better the product to the minimum standard
of quality,
During the year, the use of bactericides and bac-
teriostats were studied, and the only useful contribution to
the list previously known were glucose and ethylene oxide,
Glucose appears to have some peservative effect due to its
trimethylamine oxide and protein sparing action.
It is
probably more effective than benzoic acid, and it is the only
preservative found that complies with Pure Food laws, but it
is not r ecommended as being sufficiently effective,
Ethylene
oxide has been found to be very effective as a bactericide e
killing off as much as 99 per cent of the .contaminating floral
under conditions readily duplicated in commercial practice,
Preliminary feeding experiments in concent ra tions higher than
that used on fish show no visible toxicity to mice.
Because
12
this method may be effective in the prevention of s:lime on
bacon, our data has been given the National Research Council.
If the procees is âpplicable to the bacon trade, it is hoped
that further studies in both laboratories on the possible'
toxicity of the gas or any end products of the gas will be
made.
At the commencement of the present hostilities it
was expected that the lobster trade would be seriously
affected, and we were asked to determine the feasibility of
shipping frozen lobster meats to markets on this continent.
These experiments are now finished.
Frozen lobster cannot
be made to resemble in physical characteristics, by known
method of freezing or storage, the uncooked frozen meats.
Whether or not the consumer is willing to accept this prodluct
remains to be proven, but it is definitely inferior to the
fresh meat.
Cod liver oil production
The production of cod liver oil has almost reached
the maximumpossible with equipment now available to the trade
but only a small proportion of the livers produced aboard the
schooners can be used for the production of medicinal cod
liver oil.
The oil produced aboard the schooners engaged in
the salt fish trade is of very low quality, fit only for
industrial uses, while on the schooners engaged in the fresh
fish trade, in spite of the use of preservatives, the greater
13)
part of livers is fit only for the production of a veterinary oil.
The livers from these sources shoùld produce
under normal production a minimum of 160,000 gallone,worth
as a finished gestearinated product between 0.00,000 and
400,000,
It has not been possible to persuade captains of
fishing vessels to put aboard the ordinary steaming equipment because of the large volume of fresh water required
for the boiler,
It has been found that fine disintegration
of the livers eliminates the need of steam, the oil separating at a temperature of about 170 ° F.
This temperature
can be obtained by means of closed coils in the cooker, the
condensate being returned to the boiler.
This modified
equipment will require about half the steam horsepower of
the steam cooking, and eliminates the problem of large,
volumes of boiler water,
The livers can be ground suffic-
iently fine by means of a hammer mill, but the power demand
is somewhat high for equipment aboard the schooners,
A
grinder of our own design is under construction and it can
be reported on orally at the Annual Meeting.
A source of
supply of suitable boilers has been found and plans for a
cooker are under way.
It is hoped that this equipment will
be ready for trial aboard fresh fishing schooners before the
salt fish production starts this spring,
In connection with the preservation of livers, it
has been found that sterile livers during storage produce a,
14
darker oll than those heavily contaminated with bacteria,
Therefore any liver preservative must be not only bacteriastatic but must also prevent the action of the liver enzymes
themselves.
Experiments have shown that if intimately mixed with
finely ground liver, soda ash to one per cent of the total
weight of liver acts as an excellent preservative
Several
types. of grinders, suitable for this purpose have been found.
The companies during the present year have produced
a large quantity of oil not glite of medicinal grade.
Steam
distillation as practiced for the deodorisation of fats in
general was found to produce an oil of excellent flavour, while
even fresh oil was improved.
Equipment is being installed
for the deodorisation of these oils, adding about 50,000
gallons to our production of medicinal oilt
This is not the
direction in which we ordinarily would have desired the industry
to move, but we believe that improvements in the quallty of
un
livers brought in will render itA necessary to tcleaniupf Oil
of low quality.
A number of plant control experiments wore made on
the destearination of cod liver oil.
As a result of these
experiments one firm has remodelled its whole production equipment and- is installing destearination equipment.
A second firm
will probably install such equipment during the coming calendar
year,
15
Throughout the Whole of this work, the results
of the investigation at Prince Rupert have been of great
assistance, and Bulletin No. 59 has enabled the trade to
get a clear picture of the processes involved.
The work in co-operption with the Department of
Pensions and National Health on the vitamin value of some
of our fish liver oils has been finished in so far as this
Station is concerned,
We have assisted the Department of
Fisheries in the transport of raw material to OttaWa for
further assays.
Fish smoking
No experimental work was dune during 1940! A type
B smoke-house, erected from plans furnished by the Station,
did not function. While the faultwas found to be due mainly
to errors in construction, the smoke velocity was Pound to be
at a minimum for this type of smoking.
Examination of a
second house which had functioned properly for some years
Showed velociti.es much less than we had previously believed.
Since the margin between failure and successful operation is
so narrow, it is probably not wise to recommend further installations.
As a result of the experience in air flow gained
during the work on drying, it ehould be possible to produce a
smoke-house with a positive smoke-flow,
The interest in the
production of smoked fish is reviving. It is not deemed wise
to allow an investigation into fish smoking to interfere with
the work on drying, It is our present intention to modify
16
our mnall plant model fish dryer into a
smoker.
controlled flow
This can be done with little labour,
If the
experiment succeeds we shallbe given a stop gap until the
work on drying reaches a stage that will permit us to drop
it.
I not, it would in our opinion, be wisest to finish
the work on drying before that on smoking is given serious;
attention.
Due to the illness of the Director during the
winter and spring, field work of the Station has suffered«
Nova Scotia and Prince Edward 'bland were covered thoroughly
but no work was done in New Brunswick.
The east coast of
New Brunswick and the Grande Riviere Station will be visited
during early December.
The short courses for cannery foremen given during
February and March were poorly attended, and until more
interest is shown they should not bo repeated.
Dr. Hess and the Director attended the Conference
for Fishery Inspectors at Shediac during September, 4eading
discussions on canning, cannery grading, the inspection and
grading of canned lobster, salt fish preparation, and control
of tredt and tdun , and !putty', und fish plant sanitation.
The staff supplied technical information in the
construction of equipment for fish freeaing, fish smoking,
cod liver oil production, deodoriaation and destearination of
oils, general plant sanitation in the production of salt and
fresh fish,
17
tr. Hess cooperated with the Department of
Fisheries by reinspecting samples in all cases of underweight canned lobster detected by Fisheries Inspectors
during the 1941 season, as part of our suggested sc hema
for the s tandardization of weight inspection.
Three Progress Reports were issued during the year
and material is at hand for another issue which will appear
early in the New Year.
Because the additions to our staff
have been made relatively rocently,, the volume of publications is not large, but the work in several fields is
approaching a stat -1 that should result in a larger list for
the coming yeart
18
Scientific Staff of the Atlantic Fisheries
Experimental Station
1941
S. A. Beatty, Ph.D.
Director
Ernest Hess, M.A., Ph.D,
Associate Bactc,eriologist
W, W. Johnston, M.A., Ph.D.
Assistant Biochemist
E. P. Linton, M.Sc., Ph.D.
F.C.I.C.
Asst, Physical Chemist
A, L. Wood, BoSao, B.E.
âcientific Assistant in
Engineering
W. J. Dyer, M.Sc., Ph.D.
Scientific Assistant in
Biochemistry
A. J. Wood, M.S.A,,
Scientific Assistant in
Bacteriology
G. J. Sigurdsson, M.Sc0
Temporary Assistant in
Biochemistry
APpENDICES
SECTION
CANNED -
FISH
(With the assistance of Mr. A. H011ett , and
Homahe of the staff of the Cannsd LotietPr Controller)
Al
Appendix No ,l
LUSTER
The course of the investigations undertaken
during 1941 was determined in the main by the types of
defects unrsovered in the grading of canned lobsters
ln ,ler
the Canned Lobster Control Scheme of 1940,
WEIGHT OF CANNED LOBSTER MEAT
In the determination of the weight of the meat in
canned lobster, as set forth in the "Regulations govrning
the inspection of canned fish and shellfish and the oeeration of canneries", the cans are freely drained for a period
of not less than one minute r and not e7ceeding one and onehalf minutes.
While this arbitrary time limit has been set e
no account has been taken of the effect the temperati)re of
the can contents has on the amount cf pickle draining off
during this pericd,
Experiments have shQwn thpt the viscosity of the
pickle depends partly on the amount of so l uble protein subatances present, and increases with age of the can
as shown
in an earlier publication, but mal-Ily on the temperature of
the pickle
In most older cans ex&mined the pickle formed a
gel at 10 ° C
and even at 15 ° C, the picke is not freely
flowing in many cans * At 18-22 ° C, the pickle flow- fairly
freely, and at
a9°C
A a
it is very fluid so that the average
amounts of pickle draining off are of the order of 1 2 5 mle
at 10 ° C., 29 ml. at 15 ° C., 38 ml. at 18.5 ° C. and 50 ml, at
22°C 0
As only a fraction of the pickle adheres to the meat
itself, a part of it adhering to the can and the parchment
lining, these figures do not represent the differences in
weight of lobster meat at different temperatures,
These
amount to the following average values, taking 180,5 ° ,
an arbitrary normal: 28 ° C.
as
- 855 gme; 22 ° C, .... -4525
gin .; 15 ° C. .... 4. 4.6 gm,; 10 ° C.
+ la gme
The total
difference between 10 ° C, and 29 ° C , may therefore be an average
of 20.5 gm, or nearly 3/4 ounce,
In newly packed cans this
value would be about halved since there is less variation in
viscosity with temperature in them,
In fairness to all concerned (packers and consumera)
tests for canned lobster should be made only on cane
have been held within a certain temperature range --
weight
tha
18-23 ° C. -- for several days, or, if this is not feasible,
the results should be corrected according to the temperature
of the can content at the time of examination.
It has also been assumed by some packers that the
weight of drained lobster meat would be favourably affected
if the cans were inverted some time before opening -tem,
Accurate tests on this point have shown that no signifIcant
change in weight occurs based upon such a manipulation,
E. Hess and A. Hollett
A3
STRENGTH OF PICKLE
In the old Regulations governing the operntion of
canneries, the maximum strength of the salt brine which is
added to canned lobster was set at 2 - per cent,
This was
erroneously based on the fact that the total salt content
of fresh lobster is approximately 2i per cent without taking
into consideration that not all of this salt is sodium chloride
and that it therefore gives to the muscle a much weaker salt
flavour than a ai per cent sodium chloride content would do,
In addition, during the processing of the cans
this brine is considerably diluted by water that is cooked
out of the lobster mea, and some of the salt is absorbed by
the lobster meat to give it a pleasing salty flavour,
Tests have shown that a brine containing 8 per cent
sodium chloride when added to the can will result in a pickle
in the finished product after several weeks' storage of not
more than a per cent, and this final concentration Tas
found most pleasing in a tasting panel,
E, Hess and A, Hallett
MAGNESIUM AMMONIUM PHOSPHATE CRYSTALS IN CANNED LOBSTER
During 1941 an investiganan of the probable
causes and contributingfactors in the formation of ma€;nesium
ammonium phosphate crystals in canned lobster was begun
A4
Phosphoruà content of lobster muscle and blood
In order to arrive at the limiting factors which
affect the formation of these n struvite n crystals in canned
lobster, the natural variation of the phosphorus content of
lobster muscle and blood was considered, as it has been
observed that lobsters canned in certain areas show a much
greater tendency toward crystal formation, than those put up
in other regions, a fact which can hardly be attributed to
different canning technique, although the latter factor ba
not ignored in the investigation.
With this in view, a determknation was made of the
inorganic phosphate and organic phosphorus content of the
blood and muscle of lobsters during the pre-molt p post-mclt
and inter-molt periods,
Analyses have revealed that there is a wide variation in the phosphorus content of the blood.
(Ail figures
given here have been computed as phosphorus),
Immediately
preceding the molt, due no doubt to the absorbtion of phoephorus from the shell, it reached its highest peak, when the
total phosphorus content of the blood was found to be 27 mgp
per cent of which 13 mg. per cent was fm the form of Inorganic
phosphate,
During the inter-molt period, the concentrations
were approximately half the above figures,
It was after
molting, when the new shell had not hardened, that the loweat
phosphorus content was found,
Inorganic phosphorus in the
blood dropped to less than one mg, per cent and the total
A5
was less than 3,5 mg 0 per cent. In general there was a
greater concentration of phosphorus in the blood of the
male than in that of the female for the same period.
It was found that the concentration of phosphorum
in the muscles was not affected by the molt cycle and that
it was relatively constant,
The inorganic phosphorus
content was about 0,17 mg 0 per cent, the organic about 0411 mg.
per cent,
Analyses were also made of both the pickle and the
meat of cannedrlobster 4 some cans of which contained deposits
of struvite crystals.
In no instance was the inorganic
phosphorus content of the pickle or meat less than 0.05 mg ,
per cent,
Ëxince the solubility of magnesium ammonium
phosphate is about 0,02 - mg, per cent, it is evident that
unless e due to the presence of colloidal substances, the
solubility is greatly increased, there is present in the
meat and pickle sufficient inorganic phosphorus for the
deposition of fairly large quantities of struvite crystals;
in fact in far larger amounts than are aCtually found in
canned lobster,
This statement would be equally true if
the pickle were slightly acid at pH 6.9 whereas potentiometric
determinations have shown that the average hydrogen ion concentration of canned lobster pickle is pH 7.0, with very limited
variations,
The fact emerges, therefore, that phosphorus is not
a limiting factor in the formation of magnesium ammonium
phosphate crystals in canned lobster.
•.6
Magnesium content of lobster muscle
Preliminary alalyses have indicated that the concentration of magnesium in lobster muscle is much less than
one-tenth that of phosphore&Q.
Since magnesium is present
in sea water in greater concentration than this, it seems
probable that the washing of meat in sea water preliminary to
canning, and its use in the making of pickle may have a contributing influence on subsequent struvite crystal formation
in the canned product *
In fact, some experiments carried
that
out several years ago showed , the crystal formation was more
A
prevalent in cans in which sea water or fishery salt was used
in the pickle, than when dairy salt was used. Further investigations are being conducted along these lines.
E. Hess and A. Hollette
TEXTURE, FLAVOUR AND APPEARANCE
A series of experimental lots of canned lobster were
prepared to study the effect of such factors as overcooking of
live lobsters, overprocessing, inclusion of "sick", soft
Shelled or dead lobsters upcn the texture of the canned lobster
meat. Another series was put up to investigate the influence
of sea water and fresh watwr on the appearance (colour of
pigment and white meat) and flavour of the canned lobster meat,
particularly after prolonged storage.
These cans await
periodical examination.
E. Hess
A. Hollett
R. E. S. Homans
A/
OBJECTIVE TESTS FOR GRADING CANNED LOBSTER
In the routine grading of canned lobster during
the 1940 and 1941 seasonm only three objective tests were
used, namely determination of vacuum, weight of total lobster
meat and weight of "fine meat".
As the use of as many objective tests as possible in
the grading of any product is desirable the possibilities.ef
other tests for canned lobster have been explored.
Texture
The Armstrong penetrometer (as used in the inspeotton
of canned salmon) was tested on canned lobster, using the tail
part, i, e,, bottom part of the can e
The results appear to
give a reliable index of the average firmness of the tail
meat. They differ from the organoleptic test in so far as
the latter emphasizennot so much the average firmness but judges
the whole can by the softest tail present.
A change in the
standard for the organoleptic test would bring the two into
closer agreement,
Flavour or saltiness
The use of a salinometer is not feasible on account
of the presence of appreciable quantities of soluble proteins
and derivatives in the pickle,
Titration of a small amount of highly diluted pickle.
with a wuak solution of silver nitrate can be carried out in a
few minutes and the results are reliable.
AS
Odour
If conditions are properly arranged the odour o an
be judged with fair accuracy.
One of the difficulties
encountered in judging the odour of canned lobster is that
the odour, once the can has been opened e is extremely volatile.
To overcome this a piece of glass apparatus has been constructed
which is fitted over the can immediately after opening. This
prevents the escape of the odour.
The estimatEhon of the odour
is facilitated by the use of an attached glass tube e the open
end of which fits the nostril.
The nostrils are used alter-
nately in estimating the concentrated odour sniffed through the
tube.
Colour
Various attempts have been made to devise an objective
test which will serve satisfactorily in the estimation of pigmentation in canned lobster. Such a method has been worked out,
based on the acetone extraction of a weighed quantity of fineIy
ground lobster claw meat,
extract is then made.
A colorimetric determination of the
Suitable colour standards„ using a
mixture of amaranth and napthol
„Span also be prepared
which will accurately indicate the degree of pigmentation
thereby replacing the need of a colorimeter,
The results
obtained by using these methods indicate that they are suitable
as a referee method in the grading of colour in canned lobster.
Investigations are now being carried on to determine
A9
the feasibility of measuring the degree of pigmentation by
comparing the finely ground claw meat on a tintometer,
Such a method is extremely simple andrapid enough to serve
as a routine objective test,
Whether any or all of these tests are feasible and
valuable for routine grading romains to be determined. Their
immediate vIlue rests in their use in cases of dispute between
different graders or in borderline cases between two different
grades b
E. Hess
R. E. S, Homans
A. Hollett
EFFECT OF COOKING ON BODY LENGTH OF LOBSTERS
In the course of their duty of - enforcing lobster size
limits Departmental Officers are occasionally reaching lobster'
canneries at a time when no live lobsters are on han d ? but
batch of 'freshly cooked canning lobsters may be available for
inspection.
The question then arises whether the length of the
cooked lobster may be assumed to be the same as it was before
cooking,
The result of a test on a considerable number of sinall
canning lobsters (6,1/4 . 6e,3/4,,1ody length) was that about
one-third did not change in length during cooking l about onethird shrank 1/16 of an inch , and one-third shrank 1/8 of an
inch, From this it may be concluded that freshly cooked
AIX>
lobsters of less than 6.5/8 inches body -1,neth were under
legal size (6i inches) before cooking,' but that-botretere .,..
between 6.3/8 and 6* inches may or may not have been 61
inches long before. cooking*
E. Hess
AU
Appendix No , 2
ICELAND PACK CANNED FISH
As it was reported to us that the se-celad "Icelunge
pack of canned cod (haddock, hake) was more acceptable in the
English market than our flaked fish, "Chicken Haddies", the
preparation of this product was tried.
The essential dif-
ference in the twe products is that in the preparation of
"Chicken Haddies" gutted fish are skinned, brined and steamed,
and the edible parts picked out afterwards by hand and packed
into the cans, while in the "Iceland pack" the fish are fillotted and the skinned fillets are brined and cut into pieces
the length of the can height, (1 lb. flats).
The fillet
pieces are rolled, usually two together in a piece of parchment paper, steamed, drained and packed, three wrapped packages to a can.
In tàis method the fish muscle does not
flake apart and conseggently gives a product of a much more
attractive appearance, and suitable for a greater variety ot
ways of serving than the flaked fish.
Proper brining, steaming and processing procedure,
using suitable parchment, resulted in a very acceptable
product.
E. Hess
Ala
.toppendix No 3
POWDERED PIST1,.
101271i
MIXTURE
It has been suggested that in order to save weight
and space in shipping food, particularly fish, to Great
Britain during the war, dried ground fish might be used with
other dried and ground ingredients to have a ready-to...fry
material for fish cakes after simply adding water to the
mixture and forming the "battern into cakes,
A number of formulas were tried out usina:
Groundieckfsh
Ground dried cooked potatoes
Dried whole egg
Ground dried vegetables
Ground dried onions
Flour
Salt
with gratifying results.
Ground and dried cooked potatoes
were superior to potato flour.
flavour could easily be obtained.
Fish cakes with a pleasing
The only factor that
differed in comparison with ordinary home-made fish cakes
was the texture, which since all ingredients were of a finely
ground nature, had less body and was more of the consistency
A 13
of corn mea), pan cakes.
However this cannot be considered
a serious drawback, in view of the many advantages of the
product, particularly for export.
The tests were made with cooked fish and cooked
potatoes which had been air dried on a small laboratory
scale; it remains to be determined whether commercially
dried potatoes and fish are equally suitable.
In the
case of fish it would be a question of steam.drying in a
fish meal apparatus or air drying in a properly adjusted
artificial salt fish dryer,
E. Hess
SECTION II
SALT FISH--
A14
Appendix No. 4
SALT PENETRATION OF FISH MUSCLE
The increasing importance of salt fish in the
fishing industry along with the recent trend towards slack
salted fish, makes it essential that more knowledge be
obtained of the factors affecting the salting of cod and
similar fish.
Various workers have dealt with the salting
of herring but relatively little has been done on the less
fatty fish such as cod, hake and pollock.
The rate of salting is known to be.influenced by
several factors, e. go, kind of salt, temperature, brine con.
centration, thickness of fish, freshness of the fish, ratio
of penetration rate through skin and flesh.
Virtually
nothing is known of the giantitative influence of these
factors, and in experiments carried out through the past year
several factors have been defined.
Penetration rate in general
The results of a large number of experiments on the
penetration of salt into cod muscle immersed in saturated
brine (pure sodium chloride) at temperatures from 10 °C, to
2.0C, are summarized in figure 1„page A00, One to two weeks
are required for 'striking through', and the effect of thickness
of the fish is well shown.
One to three days are necessary for
A15
the salt content of the centre portion to reach 10 per
cent and the importance of this in allowing spoilage is
pointed out in the report on putty fish (see Appendix
7)e
Distribution of salt
The gradient of salt concentration from the
surface to the centre has been determined in practically
all cases,
This gradient is very steep particularly in
the first day or two after salting, when differences of 10
per cent or more per cm, may be observed,
Typical curves
are shown in figure ae page A a0,
Penetration through skin
Contrary to general opinion, several experiments
have shown that the aalt penetrates through the skin equally
as fast as through the cut flesh surface, the difference in
rate, If any p being less than the sampling error,
Temperature
Those in the industry have stated that fish strike
faster in warmer weather but no data. have been available,
Numerous experiments on the rate of salt penetration from O'C.
to 25'C 0 have shown considerable correlation with temperature.
For illustration a few results at temperatures of 5 ° C
20 ° C, are reported in the following table,
and
A 16
SALT CONTENT PER CENT
CENTRE
AVERAGE
Temperature 1 day 2 days 5 days 1 day 2 days 5 days
ec.
5.0
8.1
16.8
1,1
4.0
14,1
20°C,
7.2
10.2
16.8
3,5
7,2,
14.9
The difference are of the order of two and three
per cent, which in the case of the central part of the fish,
represents a200 per cent increase between 5* and 20°0, at
one day and almost 100 per cent at two days.
At five days
there is practically no difference, as might be expected.
urine concnntration
In pickled and brined fish this factor is especially
significant.
The experimental results, partially illustrated
in figure 3, page A 20, show that at two days the salt content
of the fish is about 1 per cent less for 84° pickle and a per
cent less for 70° pickle, than for Saturated brine, while the
difference is 2 and a per cent respectively at five days,
Freshness of fish
Since cod muscle softens appreciably with deterioration during storage, it would be expected that salt absorption
would be affected.
Experimentally, faster penetration was
found with increasing staleness of the fish muscle. Several
fish were stored at 0°C., 15°C., and 20°C., for about 24 hours
A17
until the fish samples at 20°C , were on the point of
The sample at 15 ° C. was slightly stale, and
spoilage.
the fish at 0°C. was unchanged ., as judged by organoleptic
tests.
The fish were then placed in saturated brine at
10 ° C., and the results of average analysis at l e 2 and 5
days are recorded in the table.
SALT CONTENT . P: R CENT
Condition
1 day
2. days
5 days
Fresh
8.4
9.9
16,2
Stale
9.1
12.3
18,6
11.1
12.9
19.2
of fish
Spoiled
While considerable differences are shown, the
increase in penetration rate is not sufficient to permit
pickling of fish in poor condition with any certainty of
success, as witness the considerable putty fish losses.
Moisture removal
In all cases molsture and salt were determined concurrently, moisture decreasing as the salt content of the protein-moisture-salt complex increased.
In fact the relation
between salt uptake and water loss is almost linear,
case of fish immersed in saturated brine.
in the
The relation cor-
responds nearly to the equation y = -1.34 x 82.0, where y Is
A18
per cent moisture and x is per cent salt , although con.i
àiderable variation is evident.
KnoWledge of the rate
of moisture removal is essential for calculation of the
rate at which salt is dissolved, due both to the absorption
of salt by the fish and to dilution of brine by the extractel
moisture, in a tank full of pickled fish,
To date the results of this investigation have been
very useful, and if further work is to be instituted
on
the
production of slack salted fish for overseas trade, they will
be essential,
Determination of the effect ef various salts
such as calcium and magnesium compounds, has still to be under.
taken, and also a comparison of the various impure commercial
salts is needed to complete this phase of the problem.
It should also be added that, due to pressure of
more directly pr actical problems at this period, insufficient
attention has been paid to a stUdy of the physical chemistry
of the migration of sodium and chloride ions in fish muscle,
and of thd chemical nature of the salt - water . protein
complex in salted:fish muscle.
This latter is intimately
bound up with drying problems.
W. J. Dyer
Fig. 1.
ABSORPTION OF SALT BY FRESH COD
SALTCONTENT
PER CENT'
Average Analysis of Whole Fish
=1Analysia of Centre Only
4--
3
4
5
6
DAYS IN PICKLE
7
8
9
10
11
1.
F1. 1.
Av, -,.
-
-
r
1 11 Fish
et
1" Fish.
3 1:
JT
1
Di =-1
8
,
r
--e,
6
6
4
4
2
2
0
0
0
-1
2
3
1
2
3
A 20
Fig. 2 , SALT DISTRIBUTION CURVES
la r. \
16'A
'-, . N.
,/
--„, , .
14-. \\''..
,
\ .,
;
,.
.
%-. la ;-',
1
\
•,,,
E-4
N
gli 10
, -. ,, .
E-4
\
;,
.:‘,..„
e
.
o
8-•
\
;
E-1
E
rn
\\
4-.
1
....
5 days
_...•-enr
)4
7vf
/
1
.--. .,e....
a days
....-
.
%
.,
'\..
1 day
._
.
A
..
,/
/
0,_
0
2
1
5
4
3
6
DEPTH - CM.
Fig. 3.
EFFECT OF BRINE CONCENTRATION ON SALT PENETRATION
ao
Cod -
18
all
thick - Average Analysis - 15 ° C,
15 days
16
SALTCONTENT OFFISH-%
14
,-
..---5 days
12
..,"
,:.
../
r. .--,-.„--
10
7
8 -
.,. -'. .
. . . . ,-*
,
, -.15--
-----
________----- ....„---.
,-----'
"
I. day
------------
_-- _...---
6
a, days
..„--
___:2„-----
-
....•
.....
,
/-
‘;
4
!-
1
L..
_1
1
o
14
84
70
SALT CONCENTRATION OF PICKLE - % SATN.
28
4Z
56
100
A
al
Appendix No. 5
.
SWELLING OF COD MUSCLE IN SALT SOLUTION
Our knowledge of the proteins present in cod
muscle and their behaviour in the presence of sodium chloride
is insufficient for anything but a superficial interpretation
of the salt penetration and moisture loss data on salt fish,
and of the drying of the cured product.
In addition, a study
of protein denaturation, and the effect of salt concentration,
time, temperature, and dehydration on this phenomenon seems to
be indicated for the slack salt fish problem, and perhaps also
for frozen fish flavour studies•
The effects of salt and hydrogen ion concentration e
singly and combined, on the swelling of finely ground cod
muscle have been determined, and a few results are plotted in
the figure, page A 22..
The curve obtained with ordinary
fishery salt lies between the one Ëiiiienfor pH 6 and that for
pH 8, and parallels the weight changes observed when cod muscle
is placed in brine.
The curve suggests that
f coagulation,
and in this case perhaps also denaturationt of the protein by
salt might not be appreciable if the salt concentration is kept
below about half-saturation.
These data may assume considerable
practical importance in attempts to market dried fish of low salt
content. •
They also show the need of basic work on the ahemistry
of the proteins In fish.musale,
W. J. Dyer
A 22
EFFECT OF pH AND
Na.C1
ON SWELLING
4.8,
5
446
Pi
4, k5.
4
o 4. , 2 i
to
VOLUME- a g. MINCED COD MUS CLEIN40
_1
W
4,0 4
1
l
3,8 1
pH 8
3,6 1
pH 6 »
-11
1
"-
\
\
\
. 2 - /7/
.///
Y
440 - J,
\ \
pH 5
7
l
2,8
•
26!
,
1
i
■ 1
a.4 .\
, \ //
2,2
\
\ ,
\\ \
/
1
Ns.
,/
\\,,
:
\'
, ...1
I
1,8 • 0
.
10
CONC. OF
,
15
L____
20
SOLN. - ge NaC1,
_1
25
30
per 100 g. H20
Satt .à,
Appendix No. 6
INVESTIGATIONS ON THE SALT TOLERANCE
OF CERTAIN FRESH FISH SPOILAGE BACTERIA
Hess (in press) has observed that certain of the
common fisherles salts possess varying powers to inhibit
the growth of the bacteria commonly associated with the
spoilage of fish.
In an attempt to obtain quantitative evaluation
of these, studies have been made on the tolerance of certain
purb,2cultures isolated from spoiling fish muscle to various
concentrations of these salts under several growth conditions.
Preliminary to the studies on salt tolerance the growth
requirements of the cultures have been investigated in some
detail.
The salt tolerance work has shown that solar salts
are
the least bacteriostatic, with mined salts in an inter.
mediate position and chemically pure sodium chloride showing
highest activity.
Perhaps of greater interest is the finding
that solar salts actually stimulate growth very markedly in
concentrations, commonly used for the treatment of fresh fish.
This stimulation may amount to several hundred per cent during
the first 48 hours of pactfflal growth.
A4
By transferring cultures through broths contining
increasing amounts of salt it has been possible to demonstrate.
that all the cultures investigated adapt themselves more
rapidly to growth in the presence of high concentrations of
solar salt.
The relationship of this finding to slime
formation in salt fish and to the development of putty fish
may be significant.
Qualitative observations have suggested that there
is a change in the metabolism of the cultures when they are
grown in the presence of solar salt.
Preliminary experiments
indicate that this may be due to traces of metallic impuritiea
in tâese salts,.
Further work is necessary for the ,.. ..omp:.,eta
elucidation of the stimulatory effect noted and for a propar •
evaluation of the various fishery salts.
A. J. Woo cR
A25
Appendix No. 7
PUTTY FISH INVESTIGATION
It was noted in the Annual Report for 1940 that
losses due to putty fish are considerable, and it is
especially pertinent at this time that these should be
avoided.
The condition is found in pickled cod and hake
during the warmer season, principally along the Prince
Edward Island and the Northumberland Straits shores.
The condition has been produced experimentally for
the first time, in large cod, at this Station.
As noted
by the industry, putty is obtained at temperatures over 70 ° F.
and its incidence is increased by diminishing the quantity
of salt used and raising the temperature of pickling. Other
work (see Appendix No. 4) has demonstrated that periods up
to three days are required for the salt concentration in
thick fish to reach 10 per ment in the central layers0
High
temperatures with low salt concentration mitigates in favour
of a rapid multiplication of various contaminating bacteria.
Chemical and bacteriological examination of the putty portion
of the fish revealed a marked increase in the number.,: of
bacteria and a parallel increase in their metaboliC% decomposition products.
With the reason for the condition estab.
Mailed, it has been possible to follow its development with
A6
time,
To do this the total numbers of bacteria as well
as the number of bacteria capable of hydrolyzing casein in
agar were determined.
The caseolytic counts were made in
an effort to detect any macro-change in the bacterial flora.
The determination of trimethylamine served as an indirect
confirmation of the bacterial counts.
Changes in the amount
of soluble nitrogen were estimated by the use of the tyrosine
reaction.
Surface pH values were obtained at the time of
organoleptic examination. From the results of these determinations it was evident that the various values increased
steadily from the outset.
This usually required from one
to three days, dependent upon the rate of salt penetration
and temperature.
Heavy pollution of the fish muscle with bacteria,
rough handling, and holding at elevated temperatures prior to
salting, and during the first three days of salting is apparently the primary cause for fish losses from this type of
spoilage.
W. J. Dyer
A. J. Wood
A27
Appendix No. 8
DRIED SLACK SALTED FISH
Preliminary work has been carried out on the
preparation of dried fish of much lower salt content than
that produced heretofore.
This work was undertàken in an
effort to produce fish dried sufficiently for shipment
overseas and of a quality acceptable to the British consumer,
using equipment either already on hand or easily procurable.
Fish only eight hours in saturated brine have been
dried under a2rtificial conditions without any occurrence of
spoilage,
These fish before drying contain 8-10 per cent
àalt, though actually the greater part of the salt is near
the surface.
If these fish are dried to about 50 per cent
water content, the salt content rises to about 15 per cent.
This product would probably compare with bacon in keeping
quality, and its palatability is excellent.
The protein&
do not seem to have been denatured appreciably, at least not
sufficiently to affect adversedly moisttlre regain and cooking
ellality, some samples dried to about 50 per cent water content
comparing very favourably in flavour with the original flab..
To date only sufficient data have been obtained to
indicate a definite possibility that a satisfactory procesa
8
can be developed. Before production on a commercial
scale can be undertaken. e the optimum conditions for
salting and drying in r elation to palatability and keuing
quality of the finished product must be determined.
W. J. Dyer
A
ee
Appendix No. 9
TEMPERATURE AND RELATIVE HUMIDITY RECORDS
Temperature and relative humidity measurements for
various points in the Maritime'Previnoes.haye been continued
along the.lines'outlined in the 1940 Annual Report,
The psychrometers on loan from the Salt Fish Board
the Station at the end of the 1940
season
wercondit a
At the' beginning of June 1941, recorders were
installed at Halifax, N. Se, Lunenburg,
and Souris, P, - E. I.
Caraquet
N. B.,
Precautienp were taken in their installa
tien in an effort to avoid repetition of last season's difficulr
ties.
Accurate psychrometric data are being obtained by the
Meteorological office of the Department of Transport, and through
their kind co-operation their recerde from Hdlifax, Liverpool, •
Yarmouth, Sydney, N. S„ and Moncton, N. 13, are available to uele
Several methods for arranging the psychrometric data •
have been:investigated.
A very conVenient way of r °cording and
• prepgmting the information, is by plottl,ng dry bulb and dew point
temperatures and relative humidities on a time basis,
print of a , seetion of ene of these graphs is attached.
A sample
A complete
analysis of the data eve4lable require's the full services of one
man. ' At the present •Unle no worker is available to carry on this
analyaià,
E 0 P. Linton
A'e L. Wood
A 30
/00
...■••■■■■
■■■■■•••••
70
6.0
1■■■•■••■
416
,e/v (5, /71./e/7
tv, S.
rlicrhfo.
/ eihe.
20
—
1
0
90
1
DA ke P01774;
7F i np&roft,/ -e and
.1-/el;fax/
99/.
80
6o
•
ç•1
1:)
_re
30
(;)
"110./e
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144lay 2?
AF
ir. s, fve,hii,
-
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Al
Al
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fris
1+ -My 28i --*1-: ikey 29 ---,---.1-" /4:9/ _34:, .H, '''.-« .'.? d.‘, H
/7
A/
s.
..w.
7,747e. i M ev .
///7/f7
- )"W(/.
Appendix No. 10
SALT FISH DRYING
The investigation of salt fish drying has been
continued on cut samples of kench cured cod using the appa.
ratus designed for t his purpose.
An improved recording
balance using a Thyraton Relay has been developed which
records weight loss with an accuracy of one twentieth of a
gram,
?revious drying results have been reviewed and tabulated and were used to direct further investigations.
The
data showed that it was not always feasible P. duplicate
results.
At first these variations were ascribed to faulty
technique in using collodion to inhibit drying from the edge&
and back of the samples.
Paraffin wax,which prevents evapora-
tion, was substituted for the collodion but variations still
exist.
It appears that these discrepancies represent either
differences in the fish themselves or in the location with
respect to the grain of the fish, from which the sample is taken,
Fifteen drying experiments, each one including several
samples, were made at a constant relative humidity of 50 per
cent.
Dry bulb temperatures of 60 ° F., 70°F. and 80.F. and air
velocities of 200 and 450 ft./min, were used.' Samples were
out from the thick part of selected kench cured cod having an
A32
average water content of 56.5 per cent and 19 per cent
salt.
Four types ofexposed surface were studied.
Razor cut surface (Figure 1, curves A, B, C,)
These samples were free from skin and bone and the
exposed surface was carefully cut smooth and flat with
a razor.
Natural cut surface
(Figure 1, curve D)
This is the washed surface originally exposed when the
cod is split before curing°
Skin surface
(Figure 1, curve E)
In these samples only the washed skin surface of the
fish was exposed to the drying air.
Ground pressed surface
(Figure 1 $ curve G)
Salt cod free from skin and bone was ground to 1/8 inch
size and pressed into cakes.
Each experiment was continued for about two days using
constant drying conditions.
Various methods for analysing and plotting the
data were tried in an attempt to determine the drying coefficients and mechanism of drying for salt fish .
A signifi-
cant method of plotting is shown Ill figure 1, in which the
fractional free water content of the sample is plotted against
time semilogarithmically.
experiments.
lehe curves are the mean of several
Each curve falls into two parts, the first
section, from zero to 550 minutes, being elliptical and the
second part, from 550 minutes on, being a straight line..;
A33
During the first 550 minutes of drying it seems
probable that a parabolic moisture distribution is being
set up in the sample and the characteristic hard surface
is formed.
The straight line portion of the curves indi-
cates that during this period drying falls into one of the
following classifications:
(a) Controlling factor: resistance to surface evaporation,
Log.(fractional free water)
Time
(Coefficient of surface evaporation)
(Thickness of sample)
(h) Controlling factor: Resistance to liquid diffusion,
Log.(fractional free water)
Time
3(diffusivity of ater)
(thickness of sample) e
Consideration of curves A, B and C, in which the
effective thickness of the samples is 7, 14, and a mm.,
respectively, shows that Log.(fractional free water) varies
Time
inversely with the thickness of the sample. Thus the drying
of these samples falls into that classification in which
surface evaporation is controlling. Hence, the drying time
would be reduced by increasing the air velocity, or decreasing the relative humidity. The interesting fact is that
under the air conditions studied, the rate of loss of water is
not controlled by diffusion of water from thick parts of the
fish to the surface layer, but presumably it is the thin, dried
A3
crut at the surface of the fish that- inhibits evaporation
of watwr to the surrounding air.
Within the accuracy of the experiments the drynte
curves for dry bulb temperatures•of 60p., 70PF. and 80 0P,
and ar, r velocities of 200 and 450 fte/Min_wiere Identical with
If velocities much lower,than 200 ft */Min. are used
curve A.
an unsatisfactory type of surface is produced,
Curves A. D e E and G illustrate the influence of the
type of txpoised. surface on the drying rate.
The skin (curve
E) dries roughly about 50 per cent as fast as a razor cut
surface (curve A) and about 45 per cent as fast as the - natural
cut surface (curve D) of the fish.
The pressed ground fish
(curve G) dries considerably faster than the other typesdf
surfqices and obviously does not follow the same type of drying
as the cut sample*
The experiments will be continued on cut samples until
optimum drying conditions are determined*
The results will
then be checked using'whole fish in the Turbo:dryer*
E. P. Linton
•
41. L. Wood
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SECTION III
FRESH FISH PRESERVATION
A6
Appendix No. 11
THE METABOLISM OF BACTERIÀ CAUSING SPOILAGE OF FISH
Investigators at the Atlantic Fisheries Experimental
Station and others have found that the decomposition of fish
muscle is primarily the result of the action of bacteria, In
the present work, the metabolism of some of these bacteria in
pure culture has been studied in the hope of elucidating its
nature,
A great number of cultures were isolated from
slightly spoiling cod muscle. By growing them in broth containing trimethylamine oxide, about 20 per cent were found to
reduce the oxide,
This is of interest since the reliability
of the trimethylamine test for spoilage has been estioned.
For further studies of their metabolism several reducers and
non-reducers were selected,
They belonged to the genera:
Achromobacter, Pseudomonas, and Micrococcus.
Their action
on glucose and lactic acid was investigated.
Throughout the;
work non.proliferating or "resting cells" were employed, the
suspensions being prepared in . the ordinary manner.
The uctIvity
activity of the suspension was found to be directly proportional to the concentration of the cells,
Before attempting to identify all the products of
fermentation the effect of changes in certain experimental
A7
conditions was investigated, since it appears that this
aspect has scarcely received sufficient attention from
previous investigators.
A comparison of aerobiosis and
anaerobiosis showed tâat the rate of fermentation of glucose
was noticeably faster in the anaerobic system, and further.
more that the presence of air had a certain definite effect
on the products of fermentation.
Thus there was in seneral
less lactic acid produced from glucose anaerobically than
aerobically.
The hydrogen-ion concentration has a very pronounced
effect on the fermentation.
In a series of experiments where
fermentation was carried out at various hydrogen-ion concen.a
trations it was found that the yield of lactic acid from
glucose was in general quite low at a high pH, but it
increased very materially as the pH was lowered.
In one
representative experiment the yield was about 20 per cent at
pH 8.1, but it rose gradually tp about 90 per cent at pH
4.6.
These results were rather unexpected, but the same
trend was demonstrated with several cultures, although in
general the difference was not qlite so pronounced.
The rate of fermentation was also greatly effected
by the hydrogen.ion concentration.
In most cases, ta21)H value
below 4.5 was almost completely inhibitory, but as the hydrogen.
ion concentration was decreased the rate of fermentation rose
to a maximum, usually at about pH 6.8.
Raising the pH further
A8
to 8.1 usually did not cause any appreciable fall from the
maximum rate.
The products of fermentation of glucose were
identified and their relative amounts were determined,•
This was done by preparing 300 ml. of the fermentation
system at pH 7.2 in a 500 ml. Erlenmeyer flask, incubating
for twenty-four hours at a5 0 c. and then analysing the
contents.
The results for certain repreeentative cultures
are shown in table I.
The effect of the hydrogen-ion con,
centration is shown in the case of Cultures 59 and PJ1 5
there being less lactic acid produced at the higher pH and
correspondingly larger amounts of the other products â
In
the results for Culture 5321, the effect of lowering of the
pH, due to acid production during fermentation, , is illus,
trated,
Where more glucose is utilized the pH has fallen
more, causing a shift in the proportionate yields of the
products,
An indication of the mechanism of fermentation le
furnished by the results for Culture 5321.
TUis culture
produces almost exactly equimolecular amounts of acetic acid
and formic acid as well as of ethyl alcohol and carbon dioxide,
suggesting that these products probably originated through
the fission of a 3-carbon intermediate. Usually such a
clear-cut relationship was not observeds
A9
The trimethylamine oxide reduced by most of the
reducing cultures amounted to between one and two millimales
per millimole of glucose fermented.
The presence of peptone in the fermentation system
was in certain cases found to accelerate the reactione
It appears from the results obtained by previous
investigators that lactic acidffunctions as the chief source
of energy for the bacteria during the initial stages of the
decomposition of fish muscle.
It was therefore surprising
to find that most of the bacteria investigated utilized
lactate very slowly.
Several cultures did) however, break
down the lactate sufficiently to permit the analysis of the
products.
In every case tested ) carbon dioxide was the chief
product derived from lactate ) the yield with different cultures
varying from 60 to 100 per cent.
This is entirely contrary
to the opinions of previous investigators regarding the fate
of lactic acid in fish muscle.
They believed that it was
broken down to equimolecular amounts of acetic acid and carbon
•
dioxidee
An interesting observation was the much more vigorous
reduction of trimethylamine oxide in the presence of lactate
thah in the presence of glucose .
Values as high as 5.8 milli.
moles Of oxide reduced per millimole of lactate fermented were
obtained.
reattione
In general the pH rose during the course of the
A40
The lactate metabolism is being investigated
further eand it is hoped that the results obtained will
furnish substantial information regarding the chemical
processes in spoiling fish muscle.
A. J. Wood
G. J. Sigurdsson
„.
.Table 1.
Culture
init pH.
59
pH 7.5
Products of fermentation of glucose by representative cultures.
Quantities are expressed in millimales per 100 ml. and in percentages of the glucose carbon metabolized.
Unitof
meaSure
ment
Glucose
used
Lactic
acid
Acetic
acid
Formic
acid
Ethyl
alchhol
mM
1.36
1.08
39.7
0.73
17.9
0.78
9.7
0.56
9.30
0.00
0.00
0.87
58.9
0.1&
5.85
0.12
2.72
0.19
8,55
0.00
0.00
Carbon
dioxide
Total
recover;
Acetyl
_ of
methyl
glucose
carbinol carbon
76.6
mM
%
0.74
pH 7.5
mM
%
1.35
0.70
26.0
1.24
30.6
0.52
19.1
0.62
15.3
0.00
0.00
0.028
1.4
_
92,4
pH 5.5
mM
%
1.86
2.77
74.5
0.45
8.06
1. 1 0
9.85
0.26
4.66
0.00
0.00
0.035
1.2
98.0-
mM
%
8.86
7.74
43.7
4.55
17.0
&.04
5.74
1.18
4.43
2.6a
4.95
mM
%
4.90
3.55
36.3
2,10
14.5
2.14
7.10
0.60
4.10
0.59
2,0
2.47
66.5
mM
%
1.60
0.70
21.9
1.06
21.9
1.02
12.5
0.33
6.2
0.35
5.7
2,30
68.5
pH 5.5
PJ1
- 5329
pH 7.2
5321
pH 7.2
(final
5.9)
pH 7.2
(Final
7.0)
76.0
75.8
>
e
ri
A 42
Appendix No. 12
FISH SPOILAGE TESTS
The use of the tyrosine test for the estimation of
the state of preservation of fish has been suggested but it
has not as yet been applied to code
It depends on the
increase in soluble protein decomposition products, principally tyrosine, tryptophane and hydrogen sulphide which arise
mainly as a result of bacterial activity but possibly due in
a smaLl measure to autolysis.
The optimum conditions for carrying out the test on
cod muscle, involving considerable simplification of the
original procedure with no loss in sensitivity, have been
established,
The tyrosin value increases steadily with time
of storage, and appears to gtve values parallel to trimethylamine and surface pH.
The test shows promise of being very
useful but as yet insufficinnt data have been accumulated to
warrant a definite statement of its correlation with the
deterioration of the fish,
An increase in inorganic phosphate was also noted
along with the increase in tyrosine and since this value may
be determined much more readily, it may prove a more practical
rapid test.
cated,
Further investigation of this question is indi-
A43
As haa been noted by Dr. A. J. Wood (Appendix No.
13),with pH, values given by surface samples show better
correlation with organoleptic tests than the samples of the
whole fish*
W. J. Dyer
A44
Appendix No.
SURFACE pH AS AN INDEX OF SPOILAGE FOR COD FISH MUSCLE
During the past few months determinations have been
made of the pH at the surface of cod and haddock fillets at
various stages of spoilage.
It has been noted that samples
taken within 2-5 mms. of the surface show marked differences
in pH depending upon the state of freshness of the fish.
Similar determinations on samples prepared from the entire
thickness of the same fillets failed to demonstrate like differences.
This result is to be anticipated since the focal
areas of spoilage must occur at the points of heaviest bacterial pollution,
In those areas trimethylamine production
is proceeding at its most rapid rate and consequently the pH
moves to the alkaline side.
The fillets tested to date have
ranged from pH 6,3 or lower for fresh fish to pH 8.5 for
spoiled.
These values, as would be expected, parallel the
trimethylamine exactly.
The chief merit of the surface deter-
mination is to be found in its simplicity and speed.
In all
cases thus far studied it has paralleled the available tests
for spoilage.
A. J. Wood
A45
Appendix No. 14
INVESTIGATIONS ON BACTERIOSTATIC DIPS FOR FRESH FISH
During the past year a number of bacteriostatic
dips for fresh fish have been examined and tested° These
have included nitrites, borates, benzoates and certain commercial preparations offered to the industry by the fishery
supply houssa.
In general, the examinations have been of a
routine character with the exception of one commercial product,
Avonex, which was studied in some detail.
Previous investigations at this Station have been
made on the value of oat flour (Avenex) as an anti-oxidant for
lobster meat and to some extent for fresh fish.
On theoretical
grounds it seemed unlikely that Avenex would be of value as a
preservative for the non-fatty fishes.
While the material ha s
proven merits as an inhibitor of autocatalytie oxidation it
seemed doubtful that this quality would delay the growth of th a
common spoilage bacteria,
Fresh fillets treated with several
concentrations of Avenex were stored and examined at frequent
intervals.
It was found that the dipped fillets kept somewhat
longer than untreateçl ones but when spoilage had begun it proceeded at a more rapid rate.
Chemical analyses of the Avenex concentrate showed, as
was anticipated, a relatively high concentration of reducing
A 46
sugar. Dips prepared to contain glucose in concentration
equivalent to the reducing sugar in the Avenex were used to
treat cod fillets.
It was found that these dips markedly
delayed the onset of spoilage ap measured ,by orgaboleptic
tests.
Repetition of the experiments on several occasions
confirmed the preliminary work. The exact mechanism for the
improvement in quality brought about by the glucose is not
immediately evidentl
Other udies on the metabolism of the
more common fresh fish spoilage bacteria have revealed that,
on the average, o'w:a
moles of trimethylamine oxide are reduced
per carbon atom of glucose fermented while with lactic acid
1.2 moles are reduced per carbon atom e
Hence it would seem
possible that the excess of glucose present in the surface
layers of the dipped fillets exerts a sparing action on the
trimethylamine oxide thus inducing an improvement in keeping
time.
Bacterial counts show that there is no decrease in
bacterial numbers in the glucose dipped fillets,
Further
work is necessary for complete elucidation of this effect,
A. J. Wood
A47
Appendix No. 15
THE VALUE OF CERTAIN GASES FOR THE STERILIZATION OF
FRESH AND SALT FISH
Innumerable attempts have been made to devise a
satisfactory treatment for the preservation of fresh and salt.
fiSh;
In general the methods developed have involved a bac-
teriostatic or bactericidal dip composed of some toxic
chemical agent.
It Can be safely said that none of these has
proved entirely satisfactory from a commercial point of Tiew,
During the past ten months a. new approach to this
problem based on the toxicity of certain gases for fish
spoilage bacteria has been attempted.
The following agenta
have been tested: ether, chloroform, methyl chloride,
methylene chloride; ethylene and ethylene oxide.
The pnly ona
of these which has fulfilled all requirements has been ethylena
oxide.and consequently a thorough study of this gas has been
made..
The work on ethylene oxide has been based on the
premise that the bactericidal activity of the gas weuld be
greatest using a vacuum system of processing,
The cost and
difficulty of producing and maintaining a reduced pressure
depends upon the reduction required..
A series of experiments
have been carried out to determine the extent of evacuation
A 48
required to give a maximum destructioh of contaminating
bacteria.
The fish were treated with 25 ems of ethylene
oxide for 25 minutes using various degrees of initial
evacuation .
The results are shown in table I.
TABLE I
Degree of
Evacuation
ems, of mercury
BACTERIA PER GRAM OF FISH AFTER SUBSEQUENT
STORAGE AT 10C, for
5
days
10
days
30
40
150,000
25,000
2,000,000
1,200,000
5,0
60
15,000
9,000
200,000
15,000
70
4,000
9,000
14,500.000
25,000.000
Control
(Untreated)
From these results it is evident that the efficiency of the
treatment increases with the vacuum drawn before admission
of the gas.
As with other bactericidal agents it is probable
that the concentration of ethylene oxide will be a determining
factor in its lethal action.
Fish were treated with various
concentrations of the gas under an initial vacuum of 70 cms ,
for 25 minutes !
*
The results are recorded in table II.
This and other stated pressures are in centimeters of
mercury,
A49
TABLE II
BACTERIA PER GRAM OF FISH
Gas pressure
Cms, of
Immediately
After 5 days'
treatment storage at 10 ° C 1
aCtor
mer cury
Control
(untreated)
10
15
20 .
as
30
280,000
22,000
3,950,000
266,000
9,200
1,600
32,500
7,700 ,
1,000
1,000
2,500
1,500
A gas pressure of 25 to 30 ems , of mercury gives a reasobable
destruction of the bacteria.
The influence of exposure time was determined by
treating fish under an initial vacuum of 70 cms. with 25
ems , of the gas.
The results are given in table III.
TABLE III
BACTERIA PER GRAM OF FISH
Time of
expo sure
After 5 dayst
Immediately
after treatment storage at 10 ° Ce
Control
(untreated)
240,000
7,000,000
"
106,400
58,800
1,750,000
600,000
30 "
40 "
600
2,300
110,000
40,000
10
20
minutes
A50
From the results of these experiments treatment
with 25 ems , of gas for 25 minutes with an initial vacuum
of 70 ems, is sufficient to greatly enhance the keeping
quality of fresh cod fillets.
The data recorded in the
above tables have been obtained a number of times with
complete agreement,
Since ethylene oxide forms an explosive mixture
with oxygen it would be advantageous to remove this hazardt.
The e xplosion hazard can be reduced by dilution of the gaa
with carbon dioxide without reducing the efficacy of treatment.
All of the work described above was carried out under
laboratory conditions.
To test the process under semi-corn-
mercial conditions a chamber was constructed of a size sufficient to treat 140 pounds of fish fillets packed in their
usual wooden shipping containers,
Results of numerous tests
made under these conditions have been in complete agreement
with those obtained in the laboratory,
It is worth while to consider the ethylene oxide
treatment in relation to the qualifications demanded of an
ideal preservative.
(1)
The preservative must be highly toxic or lethal for
all organisms associated with fish spoilage.
The experiments which have been outlined indicate that
ethylene oxide meets this requirement quite adequately.
Other experiments using pure cultures of fresh and salt
tish spoilage bacteria and molds prove that the gas is
lethal in even lower concentrations than those required
on fish muscle.
A 51
(a)
It must possess a low degree of toxicity for con.
sumers of the treated fish.
Fish which had been treated with one atmosphere pressura
of the gas for 60 minutes was fed to a colony of mice for
sixty-two days.
No ill effects could be noted in the
general condition of the mice nor could any visible effects
Perhaps the best proof that no
be noted on autopsy.
residual toxicity exists has been obtained by inoculating
a great variety of pure cultures of bacteria on fish that
had been heavily treated with the gas.
In every case the
grew
without
any
measurable
delay.
This would
cultures
seem to be excellent proof that no residual toxicity exists.
It b. as been suggested that the ethylene oxide might be converted to ethylene glycol through interaction with the
water.
The exact state of the toxicology of the latter
There
compound is not clear from the existing literature.
is general agreement that its presence to the extent of
about 5 per cent in pure solution has no apparent toxic
effect.
Determinations have been made on the total weight
From these
of gas r-equired for the treatment proposed.
values the maximum possible concentration of glycol which
could be formed if all the gas were converted to this compound is approximately .06 per cent.
If one atmosphere
pressure of the gas J‘ e used for 60 minutes of treatment
this value would be increased to approximately 0,1 per cent.
Evidence has been obtained to show that a large portion of
the gas is removed at the end of the treatment when a final
vacuum is drawn.
Thus the actual residual gas or glycol is
much lower than the approximated values even above,
On
the basis of the available information of the pharmacology
of ethylene glycol this maximum' value is far below that
The above
which can be considered to have significance.
discussion has been based on the assumption that the ethylene
oxide is converted to glycol.
The available literature on
the ethylene oxide-water reaction is contradictory.
Experiments carried out here indicate that at normal temperatures
and at the hydrogen-ion concentration of fish muscle this
reaction proceeds quite slowly.
Additional information of
considerable value could be obtained by further studies on
this reaction.
If the ethylene oxide is not converted to
glycol then the possibility of the gas remaining in the fish
as a solute must be considered.
That this is highly
improbable is fairly well demonstrated by the fact that the
fish after gas sterilization will immediately support the
growth of all bacteria tested.
This despite the fact that
very low concentrations of the gas are required to kill the
sanie organisms.
In summary it may be said, on the basis of
present data, that the ethylene oxide process meets the
second r equirement.
A52
(3)
It must penetrate through the contaminated
sections of the fish muscle.
This requirement is fully met since the muscle may
actually be rendered sterile through treatment under
the conditions described,
(4)
It must not impair in any way the appearance or
quality of the treated product.
A close scrutiny of all fish that have been treated has
failed to reveal any deleterious effects on appearance
Only with extreme gas concentrations forae
or flavour.
prolonged time can a slight whitening of the surface be
It should be noted that all investigations
observed.
have been conducted using cod and haddock in the fresh
or salted state.
Its effect in this respect on fish
such as salmon remains to bêt determined.
(5)
It must be commercially possible from the economic
point of view.
It is difficult to arrive at an accurate cost figure for
Using the best available data
the gassing treatment.
and allowing a safety margin of some 200 per cent, estimates show that the entire cost of treatment will be well
within the limits demanded by the industry.
As mentioned at the outset several other gases have
been studied t some extent but in general they have been
much less effective than ethylene oxide.
A great many other&
remain to be tried and work is progressing on these as supplies
bocome available,
If gas sterilization becomes commercially possible
it would be very desirable to make a fumdamental study of the
exact mechanism by which the gas exerts its lethal action.
This aspect of the problem has received little or no attention
since it is felt that such studies must await further practical
investigations.
A. J. Wood
A53
Appendix No , 16
PRESERVATION OF LOBSTER BY FREEZING
On the outbreak of the war the market for a great
part of the canned lobsters produced in the Maritimes was
lost. Since this product could no longer reach England and
the continent, and since at that time the Canadian and
American markets had not been developed to their present
extent the trade was anxious to find ne youtlets.
It was
pointed out that a limited market exists for lobster meata
which were cooked, then packaged and sold either fresh or
after being frozen.
As it seemed unlikely that any method
could be found for greatly prolonging the maximum storage
period for unfrozen lobster, it was decided to direct our
attention to the preservation of the meat in a frozen condition.
The trade was already preparing limited quantities
or this product.
It was reported, however, that after a few
months in cold storage, its quality had fallen greatly, the
objection being that such lobsters became spongy and tasteless.
An investigation, under rigidly controlled conditions,
of the effect of both the rate of freezing and temperature of
storage, was therefore decided upon.
Penetrometer measurements
to determine the extent of the undesirable change were tried but
fOund unsatisfactory, as there was no correlation between
A54
penetration and the r esults obtained from a tasting panel.
Similarly methods involving cutting the tissue proved
useless.
Finally it was noted that the frozen meats lose
water much more readily than the freshly cooked product.
It was therefore decided to use this as a measure of quality,
particularly of the "sponginess" of the product.
Claw meat
was also found, as a rule, to lose slightly more water under
the seine conditions than tail muscle.
The figures shown In
the following table are for tail muscle only.
In all caaes
the live lobsters were cooked for twelve minutes in boiling
water, then shelled, the meat washed and drained, and then
frozen either quickly or slowly.
When slow frozen, the
lobster meat reached a temperature of -15°C, in two hundred
and seventy minutes, when fast frozen,in fifty minutes.
The
frozen lobster meat was stored at either -15C., -10°C. or
-5 ° C.
The accompanying tabl.e shows the amount of water
which could be expressed by subjecting 100 gram of the tail
muscle of lobster to a pressure of 1,000 gram for a period of
thirty minutes.
The same apparatus to hold the muscle and
the same technique were used throughout.
The table shows
that the amount of press juice which can be expressed from
muscle increases with the period of storage.
The anount of ,
press juice from the brine frozen or qlick frozen product wam
always slightly lower than from the more slowly frozen product«
A55
The amount of press juice obtained after only eight days*
storage at -15°C. is almost 70 per cent greater than that
from the unfrozen article.
It is significant that the amount
of press juice is almost as great after two to three months ,
storage f
six months. Tasting panels composed of the
laboratory workers almost unanimously chose the fresh
unfrven meats to any which had been frozen for even twenty
four hours and none preferred the frozen meats to the
unfrozen product . There was no correlation in preference
for meats stored at the three temperatures studied. Likewise
there was no correlation in preference for vacuum packed
meats over those packed without vacuum,
Tasting panels
detected no difference between air and brine frowen meats.
Ice crystals form in the meat during freezing.
These injure the coagulum formed when the meat is cooked, and
permit the juices to escape on thawing.
This was demonstrated
by cooking egg white, freezing, and storing it at .15°C. for
ten days,
After this period, from 100 gram of egg white,
29 c.c , of press juice were recovered,
rt appears therefore
that the loss of texture parallels the increase of press juice,
Since the freezing process and a very short storage period
cause a large increase in press juice
it is believed
that no storage conditions which might be stipulated will
improve the flavour or texture of frozen cooked lobster Ieats.
It is not presumed however that the losses in flavour
A6
and texture are necessarily attributable to the same
reaction.
The former may be due to some chemical change
in the flavour-lending substances themselves, whereas the
available evidence leads one to the belief that the change
in texture Is attributable to a physical alteration in the
muscle brought about by the freezing process.
The claws and tails from live lobsters were frozen
fresh.
cooked.
After four days , storage at -15 ° C. these were
The meat was very "short", adhered tightly to the
shell and could not be removed in one piece. It had very
little flavour and apparently the juices had separated out
in the freezing process.
W. W. Johnston
A57
Air frozen.
No vacuum
Brine frozen.
No vacuum
Storage
Temperature
Press
Juice
ml.
Storage
Temperature
Press
Juice
m1.
Storage
Period
Days
0
2
3
8
60
95
134
195
-15° C.
-15 ° C.
-15°C.
-15 ° C,
-15°C.
-15 ° C,
-15 ° C.
6.0
8.0
7.2
10.1
17.5
22.0
16.8
23.6
0
83
117
195
-15 ° C.
-15°C.
-15 ° C.
6.0
14.3
18.2
17.8
0
95
195
-10 ° C.
-10 ° C.
6.0
18.0
23.2
0
95
195
-10°C.
-10 ° C,
6.0
15.6
15.7
0
95
195
-5 ° C.
-5 ° C.
0
95
195
-5 °C.
-5 ° C.
Storage
Period
Days
6.0
25.0
30.1
(incipient
decomposition)
6.0
20.5
26.1
(incipient
decomposition)
VACUUM PACK
Brine frozen
Air frozen
etorage
Period
Days
0
62
195
Storage
Temperature
-: s'_,
-i5 ° C,
-15 ° C,
Press
Juice
ml.
6.0
10.0
19.3
Storage
Period
Days
0
83
195
Storage
Tempera..
ture
Press
Juice
ml.
-15°C.
-15°C.
6.0
14,S
14.1
SECTION IV
-C 0-D.
LIVER
OIL
A58
Appendix No. 17
PRODUCTION OF COD LIVER OIL
The usual method of preparing cod liver oil
consists of placing the cod livers in vats and injecting
live steam into them.
and broken up .
In this way the livers are cooked
Considerable oil rises to the top of the
kettle and is then skimmed off.
According to the trade on
an average throughout the year 100 pounds of fish liver will
yield around 40 pounds of skimmed oil and 8 pounds more can
be recovered by pressing the liver residues.
more are lost in the residues.
About 8 pounds
Because of the prolonged
period in the press and difficulty of keeping the press cloths
clean this pressed oil is unfit for medicinal use.
It was
therefore obvious that if all the oil in the livers could be
recovered as a first class product the return of medicinal
grade oil would be increased by about 16 per cent.
An investigation into the recovery of oil from thess
liver residues showed that approximately 90 per cent of the
residual oil of a grade opal to the original, could be
recoVered
by the following process.
The residues are ground
to 40 mesh size and three volumes of hot water (about 80°C.)
and sodium hydroxide to the extent of one per cent of the
liver residues are added.
The whole is stirred slowly, after
A59
which the oil floats to the top, and much of the undigested liver residues settle to the bottom.
The saine treatment of fresh livers gave a high
recovery of oil.
Working on a laboratory scale a recovery
of 93 per cent of the total oils was obtained.
In order to produce a good grade of cod liver oil
from the livers produced by schooner fishermen, who are at
sea for periods up to a week, some form of preservation,
usually soda ash, is used.
When these livers are subse-
quently treated for the production of cod liver oil, the
oil takes on a taste and odour Which, until the substances
causing these odours or flavours are determined, we describe
as "alkaline", although an aqueous extract'obtained by
shaking the oil with water does not give an alkaline reaction.
It. was found that a great deal of the taste and
odour could be removed by three or four washings.with hot water.
A more efficient method, however, consists in steaming the
oil at 100QC. under reduced pressure.
Conditions at present
recommended are the passing of steam equivalent to 20 gallons,
of water through 100 gallons of oil at a pressure not greater
than 2 cm. of mercury and a temperature of 100 ° C,
"Alkaline"
oils treated in this manner have been reported by the, trade to
be "exceptionally good" as to colour, taste and odour.
Others
have reported them to be superior to oil made from perfectly
fresh livers.
A 60
The destearination of cod liver oil
The usual losses suffered by the trade in destearination of cod liver oil are from 20-30 per cent.
In order
to minimize these losses, experiments have been started along
two lines; firstly, the recovery of oil from the stearin
itself and secondly, experiments designed to keep the stearin
losses in the original pressing as low, as possible.
It has
been found that by subjecting the stearin from plants of two
different companies to gradual increases in pressure up to
400 *pounds per square inch from 45 to 65 per cent of the
stearin could be recovered as destearinated oil.
By determining the freezing curve of cod liver oil
it was noted that when large volumes of oil were slowly frozen
(45 gallons of oil were air frozen by placing them in a room
at 0 ° C.) that the cooling curve showed an irregularity at a
temperature of around 8 ° C.
This indicates that most of the
stearin might, if given time, crystallize out at this temperature.
If so, the crystals should be large and more easily
filtered than if the oil Were quickly super-cooled to 0 ° C.
An experiment was therefore tried in which the oil was quickly
cooled and its filtering rate compared with one whose cooling
rate passed slowly through this critical stage,.
Little dif-
ference in rate of filtration between the two oils was
observed.
This will be repeated, however, as the rate in both
cases was much higher than expected.
A1
Experiments were also carried out to determine
the effect of length of period of cold storage and on the
rate of filtration.
These showed that the rate of filtra-
tion increased from .38 ml. per square inch per minute on
oils chilled for 48 hours at 0 ° C. to 52 ml. per square inch
per minute after 17a hours cooling.
W. W. Johnston
A6
Appsndix No. 18
OBSERV0I0NS ON THE CHANGES OCCURRING
IN COD LIVERS DURING STORAGE
During the course of investigations on preserva.
tives for cod livers certain hitherto unrecorded changes
were observed.
Fresh cod livers were treated for sixty minutes.
with one atmosphere pressure of ethylene oxide gas then
stored at 2 5°C.
To compare results and to avoid varia-
tions in bacterial contamination and free fatty acid, the
fresh livers were halved and one-half was gassed while the
other was held without treatment.
As an index of spoilage
free fatty acid determinations were made at various intervals.
The livers were . examined cipalitatively for degree
of bacterial contamination at the time of sampling for free
fatty acid.
Typical results are recorded below.
Time of storage
at 25 ° C.
Fresh
24 hours
48
"
96
"
Free fatty acid
(Calculated as claie)
Gassed
Control
Per cent
Per cent
0.30
0,70
1.00
1.54
0.31
2,10
6,01
7.70
•
A6
The untreated livers decomposed rapidly and
reached a state of liquefaction after twenty-four hours of
incubation.
This change was the result of rapid bacterial
growth and is reflected in the increase in free fatty acid.
The gas sterilized livers remained sterile and retained
their identity throughout the period of incubation.
The
free fatty acid did increase at a relatively slow and
constant rate in the treated livers .
A plot of the data
showed that the untreated livers gave a typical logarithmic
products-curve which results from bacterial action.
The gas
sterilized livers on the other hand gaVe a typical curve for
enzyme action with tlke.
As the Period of incubation
increased the oil from the gas treated livers became progressively darker in colour than the oil from the untreated livers.
On closer examination the gassed livers showed that more oxihad occurred at
jItation
would seem that the
the surfaces having contact with air.
untreated livers were protected from
this change through the activity of contaminating organisms,
In addition to the use of gaseous ethylene oxide as
a liver preservative carbon dioxide ice alone and in combination with acetone, ether, chloroform and pyridine were tested,
In general, the results were in agreement with those reported
above with the exception that the ethylene oxide gas treatment
was markedly more effective in rendering and maintainig the
livers sterile,
A64
From these results it is evident that the development of free fatty acid in cod fish liver must be attributed in the main to the activities of contaminating bacteria.
While the development of free fatty acid as a result of
enzymic activity occurs at a much slower rate it is of commercial importance to the fish oil industry.
A satisfactory
preservative for fish livers must prevent the growth of all
bacteria and at the saine time prevent or delay the action of
the liver enzymes.
W. W. Johnston
A. J. Wood
A65
Appendix No. 19
VITAMINS IN LIVER OILS
As explained in Appendix 15 to the Annual Report
of the Atlantic Fisheries Experimental Station for 1940 a
systematic investigation of the vitamin potency of the fish
oils of Nova Scotia was begun shortly after the outbreak of
war.
This investigation was undertaken in co-operation
with the Department of Pensions and National Health, that
body determining the vitamin D values of te oil, and the
Station determining the vitamin A values.
Since that time,
this w ork has been completely turned over to the Department
of Pensions and National Health, and our work now is confined to seeing that the liver samples reach that Department
in good condition. Since compiling the last Annual Report
however certain values have been obtained on the vitamin
content of the liver oils of some fish of the cod species.
These are shown in the accompanying table.
The term
viscera as used in the following t able does not include
gonads or stomachs as oil from these organs shows only a
low vitamin concentration.
The vitamin A values shown
were done with the antimony trichloride reagent using an
Eyelyn colorimeter,
W. W. Johnston
f
FISH
No. of
samples Where caught
Percentage livers
Percentage viscera
in fish
in fish
Avge.
Min;
Max.
Min.
Max.
Avge.
Date of
capture
Cod
51
Terence Bay
Jan. 18, 1941
.79
5.70
Haddock
50
Terence Bay
Jan. 18, 1941
2.42
9.5 3
Hake
14
Devil's Is.
Nov. 18, 1940
1.61
July 24, 1940
July 31, 1940
Cod
8
Cod
31
Devil's Is.
Devil's Is.
2.78
2.13
6.26
3.67
5.06
4.22
8.62
6.12
7.75
5.31
1.61
3.72
2.41
1.51
4.53
2,94
4.18
5.44
4.69
1.35
4.98
3.29
2.70
6.87
3.97
•
\
•
FISH
Percentage oil
in livers
Percentage oil
in viscera
L !value of
value of
visceral oil
L
liver oil
Avge.
Min.
Max:
Avge.
Min.
3.23
.22
16.1
1.82
1.1
41.4
15.4
1.14
15.7
4.2
9.1
141,0
53.5
5.6
30.9
13.6
58.5
10.6
Min.
Max.
50.9
1.36
9.7
69.5
66.4
0.086
3.38 4.64
.098
1.1
43.4
69.0
60. 3
1.49
2.76 1.96
. .68
5.0
2.01
Cod
12.3
66.4
42.0
1.48
4.93 2.48
.65
4.2
1.29
Cod
16.1
77.2
51.0
1.31
4.97 3.07
.15
2.5
Min.
Max. .Avge.
Cod
12.4
74.5
Haddock
28.5
ake
.337
.685
.85
Max.
Avge.
SECTION
V
SMOKED FISH
A67
Appendix No, 20
FISH SMOKING
In response to several requests for information
on the construction of a small smoke-house, Type B smoke-house pamphlets were distributed,
One request of particular interest required a
house of special construction to permit its ready transportation from place to place .
This house, similar in design to
Type B smoke-house was built in Halifax and placrd in operation at West Dublin.
The first trials with kippers showed that smoking
was uneven.
A new inlet duct was installed and air
delivery to the house increased to 600 C.F.M.
A traverse of
the house with a hot wire anemometer gave air velocity readings
ranging between 40 and 8 0 feet per minute. A trial run with
200 pounds of split salted herring indicated that part of one
tier in the centre of the house was only lightly smoked.
Con-
sequently fish can not be hung in about 15 per cent of the rack
space of the house,
A Type B smoke-house which has been in operation for
over three years was examined .
order of 40-60 ft,/min,
Air velocities were of the
A 6S
In the opinion of the athors more uniform and
opitker smoking may be obtained by the positive air flow
method than by the injector type of flow as is used in the
Type B smoke-house.
Plans are being made to develop a more
satisfactory type of house along these lines of investigation.
E. P, Linton
A, L. Wood
PUBLICATIONS
The following papers have been published or subranted for publication during 1941.
Collins, V. K.
Co --11ns,
Dyer, W. Je
"Studies of Fish Spoilage.
VIII.
Volatile Acid of Cod Muscle Press Juice".
J. Fish, Res, Bd. Can. V. (3), 197-202,
1911,
"Studies of
Ke, C. C. Kuchel and S. A. Beatty
Changes in Buffering
Fish Spoilage. IX.
Capacity of Cod Muscle Press Juice".,
J.
Fish, Res. Bd, Can. V. (a), 2,03-210, 1941.
Atlantic Progress
"Salting by Weight".
Report No, 30, 0,9, 1941.
Frank, M, and E. Hess
"Studies on Salt Fish.
Survival
IV,
of Eberthella typhosa and Escherichia coli
on Salt Fish", J. Fish, Res, Bd, Can. V.
(3) ; 249-252, 194 1.
Frank, M. and Ee Hess
"Studies on Salt Fish.
Studies
V.
on Sporendonema epizoum from "dun" Salt Fish".
J, Fish, Res, Bd. Can, V. (a), 276-2,86, 1941.
Frank ; Me and E, Hess
"Süudies on Salt Fish.
Halophilic
VI.
Brown Molds of the genus Sperendonema emend,
Cif, at Red,",
J. Fish, Ros. Bd. Can, V.
(a), 287-292,, 1941.
Hess, E.
"Dun Salt Fish",
Atlantic Progress Report
No , 28, 17-19, 1940,
Hess,
"A Test to Estimate the Keeping Quality of
Fresh Fish".
Atlantic Progress Report Ne ,
30, 10-12, 1941,
EQ
Hess, E.
"Studies on Fish Spoilage.
X,
A Tost to
Estimate the Keeping Quality of Frsh Fish".
Submitted to Je Fish, Res, Bd, Can.
Hess. E,
"Studies on Salt Fish,
The Relative
VII,
Effect of Various Types of Salt on Preservatives".
Submitted to J, Fish, Res, Bd. Can.
A70
Hess, E.
Effect of
"Studies on Salt Fish.
VIII.
of
Red
H.O.ophilic
Environment upon Growth
Bacteria".
, Submitted to J. Fish. Res. Bd.
Can,
Hess, E.
The Isolation
"Studies on Salt Fish.. Ix.
of Red Harophilic Bacteria from Sea Water and;
the Slime and Intestine of Marine Fish",
Submitted to J. Fish.;Res..Bd, can..
Hess, E. and N. E. Gibbons. "Sudies on Salt Fish,
X.
Control of the Reddening of Salt Fish".
mitted to J. Fish. Res, Bd. Can,
The
Sub-
Hess, E.
"Shell Pieces in Canned Lobster".
"Proper Method of Weighing Lobster Meat",
"Brine and Pickle".
"Chilled Lobster Moat",
Lobster Canning
Circulars Nos. 18-al, 1941.
Johnston, W. W,
"The Amount of Oil Recovered by Pressing the
Cooked Liver Residue".
Atlantic Progress,
Report No. 29, 11-12, 1941,
Johnston, W. W.
"Vitamin A in Swordfish (Xiphius Gladius) and
Atlantic Progress
Tuna (Thvnnus Thynnus)".
Report No. 29, 17-18, 1941.
Johnston, W. W.
"The Sun Rotting of Cod Liver Oil".
Progress Report No, a9, 19 20, 1941,
Atlantic
-
Johnston, W, W,
"Tryptic Enzymes from Certain Commercial
Fishes",
J. Fish. £tes, Bd. Can. V. (a),
217-226, 1941.
Wood, A. J. and G. J. Sigurdsson
"Studies in Bacterial
Metabolia m
The Glucose Metabolism of
I,
Organisms Isolated from Commercial Fish".
Submitted to J. Fish, Ras. Bd. Can,
-
r
SH 223 F593 1941
Atlantic Fisheries Exper...
Annual report of the
Atlantic Fisheries...
c.1 j
12069715
L318329