Processing and Marketing AquacuItured Fish
Joe M. Regenstein, Cornell University;
Aquaculture can provide a controlled.supply of edible fish. Consumers are
often willing to gay a premium for aquaculture produced fish because of
this control. Everything from selecting the species grown-to manipulation
of the culture environment is possible through aquaculture. Superior control
should result in products with the flavor, nutrition, color, texture, and
size desired by consumers. Everyone involved in this emerging industry must
be careful to produce and market the highest quality products possible.
The purpose of this fact sheet is to summarize some important handling,
processing, and marketing concerns for the starting or expanding aquaculturist.
Handling Live Fish
Before fish are harvested, the aquaculturist should withhold feed so that
the intestinal tract is emptied. This facilitates handling and transport
as any food in the gut will present quality problems. Typically one to three
days is adequate. Longer periods may be necessary for fish maintained at
lower temperatures, but excessive time without food will lead to unnecessary
weight loss and may adversely affect quality (i.e., a softening of the flesh
as protein and/or fat is metabolized and replaced with water).
It may be desirable to maintain fish in clean, fresh water for a few days
before harvest to "rinse" them out. A problem encountered in the
culture of channel catfish in ponds and fish in recirculating systems is
off-flavor. Off flavored fish are safe to eat, but unappealing to customers.
Keeping the fish in clean water for several days to a few weeks before harvest
usually improves the flavor. This may be impractical in many situations,
but it should be a consideration when designing a facility.
As fish approach market size, samples should be tasted regularly. A sensitive
taster - i.e., the person who most readily detects off-flavor in fish --
should assume the responsibility. If fish are off-flavor, they should not
be marketed.
Methods used to harvest the fish should be carefully considered when planning
an aquaculture operation. The amount of fish harvested should be Limited
to what can be processed in one day and marketed within two to three days.
Care should be taken with fish are harvested to avoid physical damage, Handling
and contact between fish during harvest may lead to physical damage such
as bruises, punctures, scratches, and hemorrhages.
Fish should be immediately chilled boxed iced, and transported to the processing
plant after harvest Alternatively, fish may be hauled live to the processing
plant. In this case clean water and adequate oxygenation are critical. The
hauling truck should be equipped with aeration equipment. If fish are moved
a long distance, the temperature difference between the transport water
and the water from which the fish come should be less than 10 F. Adding
about 1% salt by weight to the water can reduce stress. Water can be gradually
cooled during transport to chill fish before they arrive at the processing
plant. Typically, fish destined for processing are in transit for less than
24 hours and hauled at one to four pounds per gallon of water.
A Small Processing Facility
A small-scale processing plant can be relatively simple and inexpensive
to construct It must be designed to meet all local, state, and federal regulations.
The basic requirements are tanks for live fish, a storage area for raw fish,
cutting tables for two to four persons, hot and cold potable water, ice,
waste disposal system, cleaning system (including an area for people to
wash properly), proper drainage, refrigerated storage for processed and
iced fish, freezer, certified scale(s) to weigh product at various points
in the production, and dry storage for packaging materials. Positive pressure
in the plant (i.e., the ventilation system forces in clean air) is desirable.
More information about the legal requirements for processing facilities
can be obtained from your state's Departments of Agriculture and/or Public
Health, Materials are also available from the U.S. Food and Drug Administration,
Processors must distinguish between cleaning (removing dirt) and sanitizing
killing microorganisms). The latter cannot be done until the former is complete.
Both processes must be incorporated into a formal, written. and regularly
monitored clean-up program. Most reputable cleaning/sanitizer supplies can
provide you with appropriate literature.
Facilities for people (e.g., office space, rest rooms, parking, locker,
and lunch room space) may be included. These facilities may take up more
space than the actual processing plant. All facilities should be designed
with the importance of cleanliness and sanitation in mind.
Killing
Fish can be slaughtered several ways: a blow to the head, electric Stunning,
pithing, cutting the throat ahead of the heart, chilling temperature-sensitive
species (e.g., tilapia), or simply permitting the fish to die out of the
water. Cutting the throat ahead of the heart (the most commonly used method
by commercial fishermen), electric stunning, or a blow to the head are probably
the easiest and most humane methods. The method used affects fish quality
by its effect on the postmortem biology of muscle tissue (e.g., a blow to
the head can bruise flesh). The appropriateness of different methods should
be determined and consumer perceptions should be included in the assessment
process.
Bleeding and Gutting
It is important to bleed and gut fish as soon as possible after harvest
and slaughter. Some specialists believe that live fish should be bled, left
in a rinse tank for a short period of time (about 20 minutes) and then quickly
gutted (two steps). Others believe gutting and bleeding can be done together
(one step). Insufficient evidence exists to justify the two step approach,
particularly if the fish arrive alive or were recently harvested and iced.
Therefore, for aquaculture, these two steps can be combined. This is the
routine procedure for fanned channel catfish and rainbow trout.
With some species of fish and for certain markets, bleeding and the subsequent
loss of red color in the flesh may be undesirable. However, in most cases
bleeding produces a whiter product with a longer shelf-life and better consumer
acceptance.
Gilling, Scaling, and Skinning
Fish are processed in various ways-often according to tradition. Traditional
methods may reflect industry's perception of what the consumer wants, but
may not be correct or optimal for aquaculture products. One opportunity
for the aquaculture industry is to determine consumer preferences and present
products in the forms desired.
With some species of fish and in some markets, only the gills and guts are
removed (e.g., salmon in Japan). In other markets, the fish is sold with
only the head removed. Consumer or market preferences can conflict with
processing requirements. For example, some filleting equipment requires
removal of the head. In contrast, retaining the head facilitates hand filleting
by providing a structure to hold onto while the fish is processed.
If fish are sold with their skin on, scaling may be necessary. Scales can
be removed by hand, mechanically or semi-mechanically (hand-held electrical
scaling equipment). With some fish and markets, skinning rather than scaling
is necessary (e.g., bullheads and catfish, skinless fillets). This can be
hard work. Other fish must be filleted and deboned. (Note: by definition,
a fillet does not guarantee the absence of bones. Depending on the fish,
a boneless fillet can be hard to obtain).
Chilling and Storing Whole Fish
Fish must be kept cold throughout the entire processing procedure. They
are extremely perishable; quality and shelf-life can be severely compromised
by warm temperatures. "Cold water fish" are apt to have bacteria
already acclimated to low temperatures and must be handled very carefully
to avoid spoilage.
Ice, slush ice (ice in water), or refrigerated water can be used to chill
fish. Potable water that meets local and federal regulations must be used.
Once made, the ice must be kept clean. Slush ice will cool fish faster than
plain ice because it completely surrounds the fish. Sharp edges on the ice
can lead to bruising and should be avoided. Once chilled, the fish should
be maintained as close to 32 F as possible.
Some people hold fish in a facility where the temperature is slightly warmer
than 32 F. The slightly warmer temperature encourages ice melting, which
moisturizes the fish and washes bacteria off the fish. However, the ice
water must drain away from the fish. Leaving fish in a puddle of bloody
water is a sure way to lose quality quickly by increasing bacterial contamination
and accelerating decomposition
Throughout the handling process, the fish must not be bruised or battered.
Tearing of the skin or removal of scales must be avoided, particularly if
fish are sold in the round. Appearance affects price and marketability as
much as overall quality and shelf-life.
After processing, fish should be packed on ice and put into boxes for storage
and shipping. As a rule of thumb, in summer the weight of ice in the box
should equal the weight of fish. In winter, ice should approximate half
the weight of the fish, The appropriate amount of ice to use depends on
the distance the product is shipped, whether the shipping container is insulated,
and/or whether the vehicle is refrigerated. Boxes should not be filled beyond
the natural stacking point. If overloaded. the fish will be bruised and
damaged when the boxes are stacked and quality will suffer.
Filleting
Fish are filleted on a clean table, typically a plastic cutting board. Use
of wood in food plants is being discouraged because it is difficult to sanitize
and wood splinters can contaminate the product. Ideally the fillet table
should be at a height so that the processor's arm is relaxed. An angle away
from the body of about eight degrees on the fillet table will minimize stress
and fatigue. The fillet table and work area should be rinsed regularly with
water.
Cutting the second fillet is more difficult than cutting the first because
the unsupported fish sags on the underside where the first fillet has been
removed. This often leads to a measurable decrease in yield. To correct
the problem, the cutting board may be notched. The fish head is placed in
the notch, which lets the backbone lay flat on the cutting board. This procedure
tends to slow down filleting. However, if small quantities of fish (i.e.,
custom orders) are being filleted, the increased yield might be worth the
additional time.
Skin-on fillets require special handling. Enzymes on the skin may degrade
the flesh: pigments in the skin may transfer to the fillets and ruin their
appearance. Skin-on fillets should be packed flesh to flesh and skin to
skin.
Skinning Fillets
For modest numbers of fish, fillets can be skinned with a flexible fillet
knife. Small, hand-operated mechanical skinners are also available that
can process up to ten fish per minute. Used models are widely available
at reasonable prices. In general, hand skinning yields less than machine
skinning.
Once skinned, the exposed flesh should not come in contact with ice, water
or skin. Ice and water will leach out nutrients and flavor. (However, many
processors do wash fish after filleting)!
Effect Of Processing On Yield
Each processing step reduces yield, while input of labor increases. At the
same time, more processed products command higher prices. These facts must
be considered in determining the price of the final product. Each step should
add "value" to the product and lead to greater profitability.
Many of the jobs that prepare fish for sale are relatively simple and do
not require skilled labor. However, filleting fish is a real skill--and
the differences in yield can make or break an operation. Proper employee
training and monitoring are absolutely necessary.
Packaging Processed Fish
Packaging involves more than simply combining ice and fish together in a
wet-lock box or a cooler. Plastic or metal tubs that hold 15 to 25 pounds
of processed product (without ice) are commercially available. Filled containers
can be surrounded by ice or reusable gel ice packs. Ice packs are generally
less messy than ice and less expensive if recycling is possible. The blue
colored ice gel is attractive and facilitates detection of leaks. Styrofoam
trays (often "blue" in color to signify seafood) sealed with a
clear plastic wrap can be used to package individual servings of products.
These aesthetically pleasing, simple to employ, and relatively inexpensive
processing steps can add significant value to the product before retail
sale.
Additional Processing
All food plants are subject to regulatory oversight with respect to packaging,
labeling, and good manufacturing practices. As products become more "processed,"
the potential for health risks increase. Small-scale aquaculture operations
should be cautious about proceeding into areas of further processing, such
as stuffed and precooked products.
Waste Management
"Waste" generated at a processing plant is localized and can be
recycled. Fish by-products can be used in many ways. Some can be used for
human food. For instance, mechanical deboning can produce minced fish, a
hamburger-like product which can be a healthy substitute for red meat. Many
fish by-products can be processed into pet food/animal feed products or
for non-food products such as gelatin, leather, and fertilizer. Aquaculturists
should strive to use fully their fish - the greater the return realized,
the more competitive and profitable the operation.
All of the solid waste from the various cleaning operations or unused by-products
should be disposed of properly. It is all recyclable organic matter. Sometimes
the waste can be sold to renderers. It can also be composted or made into
a fish fertilizer. For more ideas and details on management of byproducts
and fish waste, see Goldhor and Regenstein (1991).
Fresh Versus Frozen
"Fresh" is more valuable than frozen. For the aquaculturist, therefore,
it is almost always preferable to keep the product fresh (i.e., iced, and
not frozen). To minimize spoilage, fish should be kept as cold as possible
without allowing them to freeze. Even a light ice crust at the surface can
lead to undesirable textural changes.
A paradox of popular perception is that high quality fish, quickly frozen,
can be superior to fresh fish. Proper freezing and storage less than -5
F with minimal temperature fluctuations during storage) preserve quality
and make the products convenient for consumers. By minimizing loss and permitting
more efficient distribution of the product, the actual cost to the consumer
could be reduced. Unfortunately, too often poor quality fish are frozen
and cold storage is not properly regulated/maintained, so further damage
occurs. This mistreatment occurs frequently enough that many consumers have
had bad experiences. They are rightfully reluctant to purchase frozen fish.
Someday the consumer will realize the advantages of properly frozen fish,
but in the meantime the premium remains with fresh.
Transport to Market
To transport fish to market, a refrigerated truck is ideal; plastic ice
chests or similar containers will work for smaller operations that deliver
locally. Cleanliness is extremely important. Delivery schedules must be
worked out carefully to minimize transportation time and quality loss.
Hazard Analysis Critical Control Point
The U.S. Food and Drug Administration (FDA) is currently developing a "Hazard
Analysis Critical Control Point" (HAACP) program to assure the safety
of seafood at all steps in the process from capture or harvest through processing,
distribution and sale (NMFS 1991). At time of publication (1992), the approach
is being tested and is not yet mandatory. In the future, this will likely
change. Aquaculturists are encouraged to organize their processing plans
in such a way that HACCP monitoring can be easily established at their plant.
Model HACCP plans and additional information are available from the National
Marine Fishery Service (Department of Commerce, NMFS/Mississippi Lab, P.O.
Drawer 1207, Pascagoula, MS 39567, or NMFS, 1 Blackburn Drive, Gloucester,
MA 01930).
For current information on this important topic, contact your local Cooperative
Extension System or Marine Advisory Service office.
Being Customer Oriented
An important point for the small operator to remember is customer service
or "legendary service," as it sometimes is called. This may be
the most important edge for a small operation. Building rapport with end
users provides a nice difference from the more anonymous large companies
that may treat these same end users as relatively "poor" or "small
potatoes" customers. Legendary service takes work and requires "people
skills" i.e., the ability to work with people successfully. It requires
the ability to listen to your customers so that you can respond and provide
the products and services they need. That is part of the edge, part of the
control that you have over your business. Attention to details and good
luck will put you ahead of your competitors in your quest for success.
References And Suggested Readings
Goldhor, S.H. and Regenstein, J.M. 1991. Improving
the Profitability of Finfish Processing Waste: Options for Fish Processors
with an Emphasis on Mechanical Deboning (Mincing), Hydrolysis (Liquid Fertilizer
Production), and Composting, NY Sea Grant Institute, Stony Brook, NY.
National Marine Fisheries Service. 1991. Model Seafood
Surveillance Project: HACCP Regulatory Model - Aquaculture. Pascagoula,
MS.
Regenstein, J.M. and Regenstein, C.E. 1991. Introduction
to Fish Technology. Van Nostrand Reinhold. New York, NY.
Wheaton. F.W. and Lawson, T.B. 1985. Processing Aquatic
Food Products. Wiley-Interscience. New York.
Acknowledgements
I wish to thank Joseph Buttner and the other reviewers for their critical
comments on this manuscript
This work was supported by the Northeastern Regional Aquaculture Center
through grants number 89-38500-4356 and 90-38500-5211 from the Cooperative
State Research Service, US. Department of Agriculture. Any opinions findings,
or recommendations expressed in this publication are those of the authors
and do not necessarily reflect the views of the U.S. Department of Agriculture.
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Last updated March 16, 1997