Improving the quality
of commercially processed
Dungeness crab
The quality of Dungeness crab, like that of
almost any food, depends on a number of
factors, including raw product quality,
processing, packaging, and storage conditions. This fact sheet outlines some of these
important factors that contribute to increasing overall quality; more specifically, it
discusses blue discoloration, salt
content, and shelf life.
Precook handling
Improper handling causes or aggravates
most of the serious quality problems
encountered in processing Dungeness crab.
It is vital to use only live, healthy crab for
processing. Use of dead or dying crab will
aggravate quality problems through all
processing and marketing steps.
Remember: use only fresh crab! Handle
them quickly—and carefully. Do not
permit more than 16 hours to pass between
unloading and butchering. Keep crab cool
and moist (below 45° F, 7° C).
Crab intended for fresh sales are cooked
whole, whereas crab intended for picking are
butchered before cooking.
To butcher, hold the crab by the legs on
each side while bringing the belly down
sharply on a knife edge, thus splitting the
crab in two halves, each with legs attached,
called "sections." A quick shake will jar out
viscera that cling to the body cavities;
revolving nylon brushes are generally used to
clean off gills and viscera.
Oregon State University
Extension Marine Advisory Program
A Land Grant / Sea Grant Cooperative
SG 65
Revised February 1982
This publication was prepared by Jerry K. Babbitt, associate professor of food science and
technology, Oregon State University Seafoods Laboratory, Astoria, and by Kenneth S.
Hilderbrand, Jr., Extension seafoods technology specialist, Oregon State University.
Cooking
Cooling
For further information
Batch cooking is common, though a
continuous cooker has certain advantages.
The continuous cooker requires less labor,
and cooking is done without the delay of
filling a basket. It also has automatic steam
controls, and a fixed rate of travel through
the tank, assuring identical cooking with a
greatly reduced chance of human error.
For crab planned for fresh sales, cook
whole crab for 20 to 25 minutes in salted
boiling water. Crab sections intended for
picking are generally cooked in wnsalted
boiling water for 10 to 12 minutes. (Picked
meat generally is salted by a brine flotation
process for removing shell.)
For batch cooking, bring the water back
to a boil after putting in the cold crab; then
cook for the proper time. Use a thermometer
to monitor temperature during cooking.
Saltwater (4 to 5%) with a salometer
reading of 16 to 20 is normally used to cook
whole crab. Adding citric acid (0.1 to 0.2%)
to the saltwater may enhance the color of the
cooked crab by bleaching the surface of the
shell, creating a whiter color. Baking soda
has been reported to achieve the same effect,
but it acts as a buffering agent—favoring
microbial growth and shortening shelf life.
Use indirect steam to maintain the
temperature of the cook water. Coils or
steam-jacketed vessels are the most common
methods. Direct steam injection has the
advantage of being much faster, but
chemical treatments for the boiler must be of
USDA grade.
Carefully monitor cooking times for
sections. Overcooking reduces yields;
undercooked sections may be difficult to
pick. Proper cooking controls a bluish to
black discoloration of the cooked crab. If
this color change occurs, it is generally a sign
of undercooking; correct it by using proper
cook time and temperature.
Metals, particularly iron and copper, can
intensify this black discoloration. Your
water source must be free of these metals.
Do not use copper plumbing or wrought iron
cookers. Poor quality crab and the presence
of crab blood (high in copper) can also
intensify this black discoloration.
Use fresh cold water sprays or dips to cool
the cooked crab and to apply a final rinse.
Handle sections immediately, particularly
if you plan to can or retort the picked meat.
Any delay at this stage may cause a blue
discoloration in the retorted pack.
Davidson, William D., Life Begins at 40" F:
How to Use a Seafood-Handler's Thermometer, Oregon State University
Extension Service, Sea Grant Marine
Advisory Program Publication SG 32
(Corvallis, reprinted 1980).
Hilderbrand, Kenneth S., Jr., Preparation
of Salt Brines for the Fishing Industry,
Oregon State University Extension
Service, Sea Grant Marine Advisory
Program Publication SG 22 (Corvallis,
reprinted 1979).
Lee, Jong S., Cleaning and Sanitizing
Agents for Seafood Processing Plants,
Oregon State University Extension
Service, Sea Grant Marine Advisory
Program Publication SG 21 (Corvallis,
reprinted 1979).
Lee, Jong S., Hazard Analysis and Critical
Control Point Application to the Seafood
Industry, Oregon State University, Sea
Grant College Program Publication
ORESU-H-77-001 (Corvallis, 1977).
$2.00 a copy.
Packaging
If you plan to sell the crab fresh, pack
whole cooked crab and picked crab in ice
immediately. Properly handled, the shelf
life should be up to 7 days.
If you do not plan to sell it fresh, freeze the
crab or sections as soon after cooking as
possible. Brine freezing has become very
popular, but any rapid freezing system can
be as good if you take care to avoid any loss
of quality from dehydration.
OREGON STAT6 UNIVeRSFTY
EXTENSION
SGRVICG
Extension Service, Oregon State University, Corvallis, Henry A. Wadsworth, director. This
publication was produced and distributed in furtherance of the Acts of Congress of May 8
and June 30, 1914. Extension work is a cooperative program of Oregon State University,
the U.S. Department of Agriculture, and Oregon counties.
Extension's Marine Advisory Program is supported in part by the Sea Grant Program,
National Oceanic and A tmospheric Administration, U. S. Department of Commerce.
Oregon State University Extension Service offers educational programs, activities, and
materials without regard to race, color, national origin, or sex as required by Title VI of the
Civil Rights Act of 1964 and Title IX of the Education Amendments of 1972. Oregon State
University Extension Service is an Equal Opportunity Employer.