Preliminary studies on the flavor and quality of fresh N. C. blue crab meat

[From the U.S. Government Printing Office, www.gpo.gov]

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M33
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7-1 1966
No.9

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PRELIMINARY STUDIES ON THE FLAVOR AND QUALITY

OF FRESH No C.-BLUE CRAB MEAT

'S ecial Scientific Report No. 9
p

North Carolina Department of Conservation.& Development
of Commercial and Sports Fisheries
Raleigh, North Carolina

February. 1966

PRELIMINARY STUDIES ON THE FLAVOR AND QUALITY

OF FRESH N. C. BLUE CRAB MEAT*

INTRODUCTION

In recent years there has been a phenomenal rise
in the production of meat from the blue crab (Calli-
nectes sapidus) in North Carolina. In Pamlico county
alone over one million pounds of picked crab meat
were produced last year form six processing plants.
At present there is no standardization of procedure
in cooking the crabs and consequently the quality of
the product vaires a great deal from season to season
and from plant to plant. Since almost all of
meat is sold on ice as fresh product the lack of
uniform quality makes it imperative that the product
reach the consumer in the shortest possible time.
Failure to do this can resulty in spoilage of the meat
to such a degree as to make it unfit for consumption.

After crab meat is pasteurized it can be stored
at 33-37*F and still be completely satisfactory after
six months storage. Five plants in N. C. are equipped
to pasteurize crab meat and it would be beneficial
to the entire industry in North Carolina if it was
made possible for every producer to have his product
pasteurized.

A study was undertaken to establish optimum pro-
cessing conditions for the pasteurization of N. C.
blue crab meat commencing in September 1964. The
intent was to determine the cooking and pasteurization
conditions which would best preserve the flavor and
texture of the crab meat and yield a product which
would be satisfactory from the microbiological stand-
point. This report summarizes in part, the investiga-
tions of the first year of the project. Most of the
microbiological work has already been reported in
Special Scientific Report No. 6 (October, 1965)

*Distribution of this report does not constitute
publication. The data contained herein are preliminary
and are subject to correction and/or revision.

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The investigations can be subdivided as follows:

1. Organoleptic evaluations

a. Procedures
b. Pure chemicals
c. Crab meat

2. Microbioligical Studies

METHODS

1. Organoleptic evaluations.

a. Procedures.

In order to determine the effect of various
cooking and pasteurization treatments on the flavor
of crab meat it was necessary to train a group of
individuals in taste panel technique. The individuals
recruited for the panel were technicians in this
department and students with an interest in food science.
Of a total of thirty-one participants seventeen took
part in more than a third of the flavor evaluation
sessions. The remainder dropped out because of in abil-
ity to discriminate, lack of interest or inability to
attend regularly.

During the sessions the panelists were seated in a
booth designed to hold four people in such a manner
that they could individually evaluate the samples
without outside interference or distractions.
Running water and a sink for the disposal of wastes were avail-
able in each unit of the booth. No time limit was set
for an evaluation and the panelists were instructed to
attempt to judge the products as honestly and impartially
as possible. The samples under test were given code
letters or numerals and the judgements were recorded
by the participants on score sheets.

In order to familiarize the panelists with testing
procedures and some of the characteristic tastes,
aqueous solutions of pure chemicals were evaluated first,
followed later by samples of crab meat.

b. Pure chemicals.

The chemicals used in these tests were selected
to acquaint the panelists with tastes that they might
encounter with crab meat in the hope that they might
later be in a position to give meaningful descriptions

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of the flavors of different samples of crab meat. Aqueous solutinos of sucrose, tartaric acid, sodium
chloride and trimethylamine hydrochloride were used as being indicative of sweetness, sourness, saltiness
and fishiness respectively.

A threshold value was determined for each compound. This value is the concentration at which more than
fifty percent of the participants could detect the compound when compared with pure water. The results
are shown in Table 1. The table also shows the smallest detectable differences for two concentrations of the
same compound. The latter values were determined by means of triangle difference tests and two-sample
difference tests. Statistically they are very highly significant for tartaric acid. It was not possible
to determine the smallest detectable difference for trimethylamine because the panelists could not taste
other solutions after tasting one sample of trimethylamine. All the results shown in Table 1 are very close
to the values obtained by other workers and it was concluded that the taste panel was functioning in a
normal manner.

c. Crab meat.
In the evaluation of crab meat the triangle difference test was uded exclusively. In this test
three samples are presented of which two are identical and the third one is different. The panelist is
asked to identify the odd sample. The samples were coded with numerals or letters that are considered
to be psychologically pure, i.e. they give no added connotation to the sample. Examples of such codes
are K, P and S; L, T and R; 67, 34 and 85; and 52, 16 and 41. A sample of a score sheet for a triangle
test is appended to this report. The crab meat samples were kept at a constant temperature of 75*F
and the panelists were required to rinse out their mouths with distilled water at room temperature
between samples. All samples were shredded to the same degree to reduce the effect that texture might
have on the results. Table 2 shows the results of comparisons of fresh crab meat of the three standard
grades. In each case the pair under test came from
the same source.

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from the results it is clear that there is a distinct difference in flavor between claw meat and backfinmeat and between
claw meat and special meat. Except for one case all the results are very highly significant (i.e. above 0.1% clevel of probability).
On the other hand the comparison of backfin and special meats gave no clear pattern of results.

``
When fresh and pasteurized crabmeats were com-
pared, it was found that the backfin meats and claw
meats were different to the being very highly
significant.@ No significant difference was found
between fresh and pasteurized special meat. The results
are shown in Table 3. In each case.the paired-samples
came from the same plant. The fresh samples were two
days old ahd the pasteurized samples'eight days old.
In th4e case of the samples evaluated on June 23 it is
interesting to note that backfin and claw samples.yielded
very highly significant differences and yet the special
samples which came from the same lots of crab meat did
not show a difference. Much further testing would be
reuired to estimate the significance,if any of this,
observation.

.
ample- 'f -
The panel was also used "to evaluate as
canned,(cooked) blue crab meat.When compared with
fresh or with pasteurized heats every-panelist-was able
to select the odd sample. This was true both for backfin
and for special meats. Claw meat was not available.
2. Microbiollogical-studies.

In addition to the studies reported-in Special
Scientific Report No. 6 an attempt was made to inhibit
bacterial action with a chelating agent on the assumption
that this agent would bind the metallic cations reuired
for the growth of bacteria. Both ethylenediamine
tetraacetic acid (EDTA) and a combination of EDTA and
citric acid were tested. 'The compounds were added in
solution to the blended crab meat prior to plating in
an attempt to -inhibit colony-formation on the plates.
No inhibitory action was found when EDTA 12was added at
the Food and Drug Administration limitof 275 ppm.
EDTA and citric acid were also added in uantities
calculated to bind all the calcium, potassium and-iron
in the crab meat with a 25% excessand@again no inhibition
of bacterial gro08wth'was observed...

6-42-

DISCUSSION

Although the original aim of this study has not
been achieved a considerable amount of useful information
tion has been accumulated This is particularly so
the micrbiology of blue crab as detailed in

Special Scientific Report No.6. The experimental

results in that reports how that a satisfactory
microbiological,piocedure was developed which could
be used to follow the spoilage and predict the Phelf.
crab date life of crab meat stored atrefrigeration temperatures

we n
Organolptic dies that a acceptable
taste panel could be trained and that it could distin-
guish between fresh crab meat and commercially pasteure
data, were,;
ized crab meat l through microbiological
available for some of the crab meat samples evaluated
by the taste panel there as not enough of this information
tion to assess the ability of the panel to judge the
freshness of the meat. For future work the authors
recommend that a small (6-10-people) highly-trained
panel be used because it was found that the larger
group was difficult to get together at one time due to
changes in campus timetables and examinations.

In future work it would also be desirable to obtain
the crab meat from one source and to carry out all the
processing at that plant or,alternatively transport

-all the meat to Raleigh,for processing and evaluatione
This was not done in this study because the investigators

wanted to evaluate, the p d 2f2ts'f'om:the several:p
in the State.and because the facilities and labor were
not available for such an undertaking. It should also
be noted that only the flavor and microbiological
uality of crab meat was studied and that to produce
an acceptable product for the consumer consideration
must also be given to the effects that cooking and
pasteurization have on the color and texture of the
meat.

The authors do not plan to continue this work at
present for several reasponse After this study commenced
a report from the University of Maryland revealed
that work of a similar nature was nearing completion
at their seafood laboratory in Crisfield. Thus to
avoid duplication of effort and to benefit from this
work it would be wise to await the publication of
their results. In addition this study has now reached
the stage where controlled pasteurization studies
should be initiated. Unfortunately the overcrowded
conditions of our present facilities would not permit.
a satisfactory,program of pasteurization to be carried
out at this time. Therefore itis recommended that'
renewal of this project be considered in 1967 when
this department expects to be,housed in a new and
larger building on the campus and when hopefully,the,
results of the Crisfield investigations will be availables

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ACKNOWLEDGEMENTS

The authors are grateful to Dr. F. F. Busta for

helpful discus'sions :4on'the microbiological aspects of
the work to Mrs.Joyce Moore for tier competent technical assistance and to Miss Doris Holton for her part-time
help with the taste panel.

Thomson
W. A. B
and
F. B. Thomas
Department of FoodScience
North Carolina State University
Raleigh, North Carolina

Table 1.

Threshold.valu'es and detectable difference
values for pure chemicals in water*

Threshold Solutions with a
value in water detectable difference
Flavor
Chemical Sensation Rercent - percent

Sucrose sweet 0.125 0.5 and 1.0

Tartaric acid sour 0.005 0.01 and 0.015

ty
Sodium chloride sal 0.025 0.25 and 0.35

Trimethylamine fish' 0.00125.
y

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Table 2.

Results of triangledifference
-on
tests., Dairs-:of .,crab. meat %jzrades.

Age of crab' Number of No,* of 'correct Statistical
Date meat, days-'.panelists judeements
sienificance

(a) backfin vs. sy)ecial

25 Feb'1965 4 .18 .7 none

none
:1965 5 17
8 Mar', 6

9 Mar 1965 6 16 none
2;_

Mar-1965 7 @17. 11 'highly significant-

22 Apr 1965 1 32 10 none

29 Apr 1965 4 22 11 none
29 Apr 1965 7 11 7 significant
18 May 1965 4- 24 17 very highly
significant

20.May 1965 3 10 none
May, 1965 3_ 18 12, highly significant
10 Jun 1965 2 26 17 very highly
significant

19 Aug 1965 3 .26 12 none
(b) backfin vg. cla-_

11-Mar 1965 8 17 14 very highly
significant

25 Mar 1965 1 15 9 significant
22 Apr 1965 1 16 14 very highly
significant

20 May 1965 3 10 10 very highly
significant

11 Mar 1965 8 17 14 very highly
significant,
22 Apr. 1965 1 16 15 very highly
significant
20 May 1965 3 -10 10 very highly
significant
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Table 3

Re sult s "of iang le difference tests on
:fres'h`ahd pasteurized crab meat.

Date Number of No. of correct Statistical
panelists judgements significance

(a) hankfi

25 Mar 1965 15 14 verybighly
significant.

.23 Jun 1965 .26 18 very highly
significant

.-.special

23 Jun 1965 22 10 none

23 Jun 1965 24 14 significant

24 Jun 1965 22 16 very highly
significant

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Pat-P,

Test No.

Any of these samples may or may not be different-from the
other two, Please taste, the samples and check one of the following
categories

Samples are different

The odd Sample is sample

Samples are not different.

No decision (all samples taste
different).

Name

Date-

Test No,,

Any of these samples may or may not be different from the
other two, Please.tastei,the.-samples and check one of the following
categories,@

Samples are different.

The odd Sample is sample

Samples are not different.

No.decision (all samples taste
different).

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