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 Introduction and methods
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Group Title: Technical paper -- Florida Sea Grant College Program ; no. 36
Title: Microbial and nutritional attributes of soft crabs
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 Material Information
Title: Microbial and nutritional attributes of soft crabs
Series Title: Technical paper Florida Sea Grant College
Alternate Title: Soft crabs, Microbial and nutritional attributes
Physical Description: 6 p. : ; 28 cm.
Language: English
Creator: Otwell, W. Steven
Koburger, J. A
Florida Sea Grant College
Publisher: Sea Grant Extension Program
Place of Publication: Gainesville Fla
Publication Date: 1985
 Subjects
Subject: Crab fisheries   ( lcsh )
Blue crab industry   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 4.
Statement of Responsibility: W.S. Otwell and J.A. Koburger.
General Note: Grant NA80AA-D-00038.
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00075987
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 17445040

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Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Reprint information
        Unnumbered ( 3 )
    Introduction and methods
        Page 1
        Page 2
    Results and discussion
        Page 2
        Page 3
    References and acknowledgements
        Page 4
    Tables
        Page 5
        Page 6
        Page 7
Full Text


Technical Paper No. 36.


HUME LIBRARY
APR 1 1986
I.F.A.S.- Univ.. of Fiorida


MICROBIAL AND NUTRmONAL ATTRIBUTES

OF SOFT CRABS

by
W. S. Otwel
and
J. A. Koburger


















FLORID A A ORANT COLLEGE TP-36












MICROBIAL AND NUTRITIONAL ATTRIBUTES


OF SOFT CRABS




W. S. Otwell

and

J. A. Koburger


Department of Food Science and Human
University of Florida
Gainesville, FL 32611


Nutrition


Project No. SGEP-8
Grant No. NA80AA-D-00038



Technical Papers are duplicated in limited quantities for specialized
audiences requiring rapid access to information and may receive only
limited editing. This paper was compiled by the Florida Sea Grant College
with support from NOAA Office of Sea Grant, U.S. Department of Caomerce,
grant number NA80AA-D-00038. It was published by the Sea Grant Extension
Program which functions as a component of the Florida Cooperative Extension
Service, John T. Woeste, Dean, in conducting Cooperative Extension work in
Agriculture, Home Economics, and marine Sciences, State of Florida, U.S.
Department of Commerce, and Boards of County Crmmissioners, cooperating.
Printed and distributed in furtherance of the Acts of Congress of May 8 and
June 14, 1914. The Florida Sea Grant College is an Equal
Employment-Affirmative Action employer authorized to provide research,
educational information and other services only to individuals and
institutions that function without regard to race, color, sex, or national
origin.





TECHNICAL PAPER NO. 36
September 1985






















































Reprinted from the proceedings (in print) of the National Symposium on the
Soft-shell Blue Crab Fishery, Biloxi, Mississippi, February 12-13, 1985.
Sponsored by the southeast Marine Advisory Services Network and the Sea
Grant Mid-Atlantic Advisory Services Network. For further information on
the proceedings, contact Harriet Terry, Editor, Gulf Coast Research
Laboratory, Ocean Springs, MS 39564. (601) 875-2244.












MICROBIAL AND NUTRITIONAL ATTRIBUTES


OF SOFT CRABS



INTRODUCTION

Soft-shelled blue crabs (post molt hard blue crab Callinectes
sapidus, continue to be sought as a special, high priced culinary delight.
Based on current costs per pound (: $8.00/lb. retail) the soft crab remains
one of the highest priced seafood selections. Although consumption figures
are not available, recent increases in domestic production and prices
suggest consumer demand continues to exceed supply. In Florida alone,
there was essentially no production prior to 1978; whereas, the 1983
production was in excess of 50,000 pounds with a dockside value above
$70,000 dollars (Andree, 1985). In light of these developments more
information is needed regarding the handling and storage of the product,
and to explain their relative dietary contribution. Cmamon retail practice
is to store pre-wrapped soft crabs either frozen ( 0 F; -18 C) or fresh
(400 F; 4.2' C). Based on camnercial experience, the frozen shelflife for
properly packaged soft crabs can exceed 12 months. However, there are no
reports on the reccmnended refrigerated shelflife. Likewise, there is no
formal published data on the nutritional constituents of soft crabs. This
report addresses these issues.
METHODS

Soft crabs were obtained from a commercial shedding facility in
Cedar Key, Florida. This operation used common procedures for holding
pre-molt hard blue crabs in flow-through water systems. The water used was
drawn from the adjacent brackish waters which have been monitored to meet
water quality standards sufficient for harvest of shellfish (FL Dept. of
Natural Resources, Dept. Rules, Chapter 16B-28; median fecal coliform Most
Probable Number (MPN) of water shall not exceed 14/100 ml and not more than
10% of the samples shall exceed 43/100 ml.) Crab samples were taken during
spring (May) and fall (October).

The post molt samples were immediately wrapped in plastic film and
held on ice prior to initiating analyses. Microbial analyses began within
24 hours (0 day) after shedding. Nutritional analyses were performed on
spring samples pre-frozen on zero (0) day. All analyses used the entire
edible portion (whole crab dressed or cleaned with gills, apron, eyes and
mouth parts removed). The crabs were cleaned just prior to analyses.

Microbial analyses included aerobic plate counts (APC) with
incubation at 250 C. Fecal coliforms and Vibrio parahaemolyticus were
tested by methods outlined in the Food and Drug Administration's
"Bacteriological Analytical Manual," (FDA, 1978). All analyses were
conducted in duplicate per sampling day (0, 2, 4, 6 and 8 days storage).












Nutritional analyses included proximate composition (AOAC, 1980),
minerals (Na, K, Ca, P, Mg, Zn, Fe, Cu, Mn, Cd, and Hg) and fatty acids.
Gall et al. (1983) should be referenced for more specific methodology.
Mineral analyses employed an atomic absorption spectrophotmaeter
(Perkens-Elmer Corp., Model PE503 and 5000). Ashed samples were dissolved
in a final concentration of 0.2N hydrochloric acid. Phosphorus was assayed
colorimetrically using tartrate-molybdate-ascorbic acid reagent, and
Mercury was determined by the Perkens-Elmer Mercury Analysis System.

Fatty acids were determined by methyl ester preparations (McCreary,
et al., 1978) separated by gas-liquid chromatography (Hewlett Packard Model
5840-A gas chramatograph) equipped with a Hewlett Packard Model 7671-A
automatic sampler and 6 ft., 4 mm i.d. columns packed with 10% Silar 10 C -
Applied Science Labs. Acids were identified by comparison with retention
times for pure fatty acid methyl ester references (Nu Chek Prep, Inc.)

RESULTS AND DISCUSSION

High microbial counts coupled with adverse product evaluations
indicate soft crabs have a relatively short refrigerated shelflife (Table
1). After six days storage below 350 F (1.70 C) or on ice, the average
microorganisms per gram (APC, 250 C) ranged from 0.2 to 1.2 x 10 The
crabs had became flaccid, exuding excess weepage with obvious slime and
objectionable odors. The raw product was judged unacceptable on the sixth
day of refrigeration. This result is expected realizing the vulnerable
nature of the initial crab tissues infilterated with a high moisture
content resulting from the natural, untreated water supply and no
subsequent washing. Attempts to treat the water supply to better
facilitate crab survival and lower initial microbial counts would not
necessarily assure an extended shelflife. The soft, moist condition of the
crab tissues is apparently a suitable media for prolific bacterial growth.
The low counts for fecal coliforms is a favorable reflection of the water
quality and attest to the use of water monitoring by standard conditions.

The detection in the crabs of the potential pathogen, Vibrio
parahaemolyticus is common for seafoods from similar areas and should not
pose a health threat unless careless handling affords a chance for
cross-contamination with cooked, or ready-to-eat items. Retailers should
be warned of the consequences and exercise care in handling and storage,
i.e., do not store raw soft crabs near or with cooked crabs or with other
ready-to-eat seafoods, and never reuse soft crab packaging or containers to
hold cooked items. Note that parahaemolyticus did decrease during
refrigerated storage.

The high moisture content contributing to the bacterial growth was
evident in the proximate analyses (Table 2). Typically, raw blue crab meat
has a moisture and protein content of approximately 80 and 16 percent,
respectively (Sidwell, 1981). The protein content in immediately post-molt
blue crabs is lower due to the lower proportion of muscle tissues. The












Nutritional analyses included proximate composition (AOAC, 1980),
minerals (Na, K, Ca, P, Mg, Zn, Fe, Cu, Mn, Cd, and Hg) and fatty acids.
Gall et al. (1983) should be referenced for more specific methodology.
Mineral analyses employed an atomic absorption spectrophotmaeter
(Perkens-Elmer Corp., Model PE503 and 5000). Ashed samples were dissolved
in a final concentration of 0.2N hydrochloric acid. Phosphorus was assayed
colorimetrically using tartrate-molybdate-ascorbic acid reagent, and
Mercury was determined by the Perkens-Elmer Mercury Analysis System.

Fatty acids were determined by methyl ester preparations (McCreary,
et al., 1978) separated by gas-liquid chromatography (Hewlett Packard Model
5840-A gas chramatograph) equipped with a Hewlett Packard Model 7671-A
automatic sampler and 6 ft., 4 mm i.d. columns packed with 10% Silar 10 C -
Applied Science Labs. Acids were identified by comparison with retention
times for pure fatty acid methyl ester references (Nu Chek Prep, Inc.)

RESULTS AND DISCUSSION

High microbial counts coupled with adverse product evaluations
indicate soft crabs have a relatively short refrigerated shelflife (Table
1). After six days storage below 350 F (1.70 C) or on ice, the average
microorganisms per gram (APC, 250 C) ranged from 0.2 to 1.2 x 10 The
crabs had became flaccid, exuding excess weepage with obvious slime and
objectionable odors. The raw product was judged unacceptable on the sixth
day of refrigeration. This result is expected realizing the vulnerable
nature of the initial crab tissues infilterated with a high moisture
content resulting from the natural, untreated water supply and no
subsequent washing. Attempts to treat the water supply to better
facilitate crab survival and lower initial microbial counts would not
necessarily assure an extended shelflife. The soft, moist condition of the
crab tissues is apparently a suitable media for prolific bacterial growth.
The low counts for fecal coliforms is a favorable reflection of the water
quality and attest to the use of water monitoring by standard conditions.

The detection in the crabs of the potential pathogen, Vibrio
parahaemolyticus is common for seafoods from similar areas and should not
pose a health threat unless careless handling affords a chance for
cross-contamination with cooked, or ready-to-eat items. Retailers should
be warned of the consequences and exercise care in handling and storage,
i.e., do not store raw soft crabs near or with cooked crabs or with other
ready-to-eat seafoods, and never reuse soft crab packaging or containers to
hold cooked items. Note that parahaemolyticus did decrease during
refrigerated storage.

The high moisture content contributing to the bacterial growth was
evident in the proximate analyses (Table 2). Typically, raw blue crab meat
has a moisture and protein content of approximately 80 and 16 percent,
respectively (Sidwell, 1981). The protein content in immediately post-molt
blue crabs is lower due to the lower proportion of muscle tissues. The











protein loss is balanced by an increase in water content, which is actively
taken in to expand the new molt. There is also more ash content resulting
from the higher proportion of tissue destined to be shell. Notice that
lipids are not significantly different.

The mineral composition is likewise a reflection of the higher
proportion of shell material and the metabolic state immediately post-molt
(Table 3). The sodium (Na), Calcium (Ca) and phosphorus (P) content in the
soft crabs was substantially higher than that reported for raw hard crab
muscle tissue (Sidwell, 1981). These concentrations reflect the osmotic
state of the crab and the high calcium content can be explained as a
necessary constituent for shell formation and hardening. The micraminerals
are similar to previous reports except for the lower concentrations of zinc
(Zn) and copper (Cu). These minor minerals are primarily associated with
muscle growth and function, thus they should be initially low due to the
lower proportion of protein found in soft crabs. There was no detection of
mercury (Hg) or cadmium (Cd) with detection methods limited to 0.01 ug/ml.

The fatty acid profile is similar as for most lean varieties of
seafoods (< 2% lipid) with a high concentration of polyunsaturated acids
(Table 4). The monosaturates and polyunsaturates constituted 21.48% and
33.26% of the total fatty acids, respectively. In comparing the
polyunsaturates to saturates ratio for soft crabs (PUFA/SAT 1.48) the
soft crabs appear more saturated than raw hard crab meat (1.34; Sidwell,
1981) and pasteurized crab meat (1.32; Gruger, et al. 1964). Apparently,
the post-molt condition does not significantly influence the total fat
content, but does alter the fat composition comparee tables 1 and 4).

These basic nutritional constituents in raw soft crabs would be
altered by cooking as reported for other seafoods (Mai et al., 1978; Gall
et al., 1983). If breaded and fried, the customary method for preparation,
the soft crab moisture content should decrease causing a slight increase in
protein content. These changes would not represent a major alteration in
the nutritional value. The addition of calories from breading and absorbed
frying oil would cause the most significant changes. The fat content and
composition per serving would increase and change to reflect the character
of the frying oil. Likewise, the breading formulation could dominate the
mineral composition, particularly sodium content. Fried soft crabs would
represent a seafood with relatively high salt content. Based on the raw
composition, 486 mg Na/100 g crab (Table 4), plus additions from breading
and cooking dehydration, a fried soft crab could provide in excess of 130
mg sodium per 4 ounce serving. In general, fried soft crabs should be
considered a typical lean variety of fried seafood with a higher than
average amount of sodium. Persons on a low-sodium restricted diet may
consider alternative non-fried recipes and/or consumption in moderation.










REFERENCES


Andree, S. 1985. Status of the Soft-Crab Fisheries in Florida. Proc.
National Symposium on the Soft-Shelled Blue Crab Fishery.
Biloxi, MS. (In this text)

Association Official Analytical Chemists (A.O.A.C.). 1980. "Official
Methods of Analysis," 13th Ed., Washington, DC.

Gall, K.L., W.S. Otwell, J.A. Koburger and H. Appledorf. 1983.
Effects of Four Cooking Methods on the Proximate, Mineral
and Fatty Acid Composition of Fish Fillets. J. Food Sci.
48:1068.

Gruger, E.H., R.W. Nelson and M.E. Stansby. 1964. Fatty Acid
Composition of Oils from 21 Species of Marine Fish,
Freshwater Fish and Shellfish. J. Am. Oil Chem. Soc. 41:662.

Mai, J., J. Shings, J. Weihrauch and J.E. Kinsella. 1978. Lipids
of Fish Fillets: Changes Following Cooking by Different
Methods. J. Food Sci. 43:1669.

McCreary, D.K., W.S. Kossh, S. Ramachandran, and R.R. Kurtz. 1978.
A Novel and Rapid Method for the Preparation of Methyl Esters
for Gas Chramatography: Application to the Determination of
the Fatty Acids in Edible Fats and Oils. J. Chrmnatog. Sci.
16:329.

Sidwell, V.D. 1981. Chemical and Nutritional Composition of
Finfishes, Whales, Crustaceans, Mollusks, and their Products.
U.S. Dept. Ccmn./NMFS Technical Memorandum NMFS F/Sec-ll.
432 pp.

U.S. Food and Drug Administration. 1978. Bacteriological
Analytical Manual. 5th Ed. Assoc. of Official
Analytical Chemists. Washington, DC.



ACKNOWLEDGEMENTS

The authors wish to acknowledge the technical assistance of Food
Science graduate students Jeff Bellairs, Ken Gall and Mary Miller.









Table 1. Aerobic plate counts (APC, 25C microorganisms (g), fecal
coliforms (FC HPN/g) and Vibrio parahaemolyticus (VP -
positive samples/3 samples tested) for whole, raw soft
crabs stored on ice in refrigeration (35F; 1.7C).




Spring Fall
Storage (May) (Oct.)
(Days) APC FC VP APC FC VP



0 2.5 x 106 < 2 3/3 2.0 x 105 < 2 2/3

2 9.7 x 106 < 2 2/3

4 4.6 x 10 < 2 0/3 1.4 x 106 < 2

6 1.2 x 108 < 2 2/3 2.2 x 107 < 2

8 2.3 x 108 < 2 0/3



Table 2. Proximate composition (%) for whole, raw blue crabs.




1 2
Soft Blue Crab Hard Blue Crab


Moisture 84.68 + 0.25 80.3 (77.4 86.7)3

Protein 10.91 + 0.53 15.9 ( 8.6 19.8)

Fat 1.40 + 0.06 1.3 ( 0.4 2.2)

Ash 2.84 + 0.10 1.9 ( 1.3 2.7)

Total 99.83



IEach soft crab mean value and standard deviation () represents

eight replicates where one replicate is for one whole crab

blended for analysis.

Source: Sidwell, 1981.

3Range.









Table 3. Mineral analysis for whole, raw blue crabs.


1 2
Minerals Soft Blue Crab Hard Blue Crab


--------------- g/100g
486.4 + 23.57

249.71 + 6.89

422.35 + 47.79

309.14 + 52.46

64.53 + 3.55

------ ------/lOOg

22. 0 + 1.0

4.28 + 0.55

18. 8 + 0.8

6.00 + 0.78

4N.D.

N.D.


-----------------------
337

244 ( 188 299)3

115 ( 60 277)

174 ( 38 272)

32 ( 12 47)

---------------------


23.17

9.36

40.24


( 2-

(1.3 -

( 34 -


54)

19.0)

46)


lEach soft crab mean value and standard deviation (+) represents

eight replicates where one replicate is for one whole crab blended

for analysis.

Source: Sidwell, 1981.

Range.

4Not detected.









Table 4. Fatty acid profile (% composition of total fatty
acids) for whole, raw soft blue crab.




1
Fatty Acid Percent

14:0 3.99 + 0.48
14:1 ( 9 + 15:0 3.21 + 0.50
16:0 18.75 + 0.90
16:1 w 9 8.59 + 0.39
17:0 3.62 + 0.37
18:0 8.54 + 0.61
18:1 a 9 9.68 + 0.69
19:0 0.53 + 0.30
18:2 o 6 1.62 + 0.73
20:0 0.99 + 0.40
20:1 ( 9 + 18:3 a 3 5.39 + 0.80
20:2 0 6 1.60 + 0.39
22:0 0.54 + 0.24
20:3 a 6 0.30 + 0.14
20:4 c 6 5.43 + 0.23
22:2 o 6 2.14 + 0.14
20:5 o 3 7.35 + 0.31
22:3 ( 6 0.27 + 0.19
22:4 a 6 1.25 + 0.36
22:5 w 3 1.18 + 0.07
22:6 o 3 6.76 + 0.47
Others 8.31 + 0.82
Total 100.04



1Each mean value and standard deviation (+) represents
eight replications were one replicate is one crab blended
for analysis.




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