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SMART PRODUCTIONON
SMART PRODUCTI

quickly, then the ice crystals will remain small and
cause minimal damage to the cells. Fish that passes
through the zone of maximum ice crystal formation
in less than one hour will generally have minimum
drip loss upon thawing.
- Cold Storage: Once fish is frozen, it must be
stored at a constant temperature of -23 °C (-10 °F)
or below in order to maintain a long shelf life and
ensure quality. A large portion of fresh fish is water
(e.g., oysters are more than 80% water). Because
the water in fish contains many dissolved substances, it does not uniformly • Irradiating: Irradiation offers a means of pasteurizing or sterilizing
freeze at the freezing point of pure water. Instead, the free water in fish a variety of food products. However, the use of this process has not
freezes over a wide range, beginning at approximately -2 °C (28 °F). The been universally accepted throughout the food industry.
amount of remaining free water decreases until the product reaches a Food irradiators utilize radioisotopes, such as cobalt-60 (60Co) or
temperature of approximately -40 °C. Fish held below that temperature cesium-137 (137Cs), or electron beam generators to provide a source
and packaged so as not to allow water loss through sublimation can be of ionizing radiation.
stored for an indefinite period. Unfortunately, there are relatively few The irradiation of seafood has been extensively studied since the
commercial freezers capable of storing fish at -40° C because of the 1950s. The pasteurization of fresh fish using low-level dosages of
tremendous variation in energy costs. Fish are therefore normally stored ionizing radiation may extend the shelf life of the product up to several
at -18 to -29 °C (0 to -20 °F), resulting in a variable shelf life ranging from weeks. The sensory and nutritional characteristics of the fish are
a few weeks to almost one year. unaffected at these low levels of radiation.
• Controlling Water Activity: Reducing the water activity of fish
inhibits the growth of microorganisms and slows the chemical reactions Total Utilization of Raw Materials
that may be detrimental to the quality of the fish product. The control of In response to an increased demand for “ready-to-eat” fish products,
water activity in fish is accomplished by drying, adding chemicals, or a along with a growing awareness of the limited supply of natural fish
combination of both methods. stocks, the fish industry has developed procedures for more efficient
- Drying: The principal methods of drying, or dehydrating, fish are by utilization of available raw materials. Because as much as 70% of
forced-air drying, vacuum drying, or vacuum freeze-drying. Each of these harvested fish has traditionally been discarded or converted into cheap
methods involves adding heat to aid in the removal of water from the fish animal feeds, initial efforts to conserve fishery resources have focused
product. During the initial stages of drying, known as the constant-rate on the development of edible products from underutilized species.
period, water is evaporated from the surface of the product and the - Surimi: Surimi was developed in Japan several centuries ago
temperature of the product remains constant. In the final stages of drying, when it was discovered that washing minced fish flesh, followed by
known as the falling-rate period, the temperature of the product increases, heating, resulted in a natural gelling of the flesh. When the surimi was
causing water to move from the interior to the surface for evaporation. combined with other ingredients, mixed or kneaded, and steamed,
- Curing: Curing reduces water activity through the addition of various fish gel products called kamaboko (fish cakes) were produced
chemicals, such as salt, sugars, or acids. There are two main types of and sold as neriseihin (kneaded seafoods).
salt-curing used in the fish industry: dry salting and pickle-curing. In dry The chemistry of the surimi process involves the differential
salting the butchered fish is split along the backbone and buried in salt extraction of muscle proteins. The water-soluble sarcoplasmic proteins
(called a wet stack). Brine is drained off until the water content of the flesh are removed during the washing of the minced flesh. These proteins
is reduced to approximately 50% (the typical water content of fresh fish inhibit the gelling properties of the minced flesh. The flesh is then
is 75-80%) and the salt content approaches 25%. In heavy or hard-cure comminuted with salt, which solubilizes the myofibrillar proteins actin
salting, an additional step is taken in which warm air is forced over the and myosin. Upon heating, the myofibrillar proteins form a network
surface of the fish until the water content is reduced to about 20% and structure that takes on a gel-like consistency. Cryoprotectants are
the salt content is increased to approximately 30%. Most dry-salted fish necessary to stabilize the myofibrillar protein network during frozen
products are consumed in warm, humid countries. storage.
In pickle-curing, fish are preserved in airtight barrels in a strong pickle - Minced Fish Flesh: The success of surimi-based products has
solution formed by the dissolving of salt in the body fluids. This curing stimulated the development of other products made from minced flesh.
method is used for fatty fish such as herring. Minced fish products do not undergo the repeated washing cycles
- Smoking: Traditionally, smoking was a combination of drying and necessary for the production of surimi. Because of the presence of
adding chemicals from the smoke to the fish, thus preserving and adding residual oils and sarcoplasmic enzymes (both oil and sarcoplasmic
flavour to the final product. However, much of the fish smoked today is proteins are removed during the washing of surimi), cryoprotectants
exposed to smoke just long enough to provide the desired flavour with must also be added to the minced flesh prior to freezing in order to
little, if any, drying. These products, called kippered fish, have short shelf protect the product from oil oxidation and enzyme degradation.
lives, even under refrigeration, since the water activity remains high Minced fish flesh is used in a wide variety of products. The largest
enough for spoilage organisms to grow. volumes are extruded into formed patties for main dishes and
The smoking process consists of soaking butchered fish in a 70-80% sandwiches. The forming process involves combining the minced flesh
brine solution for a few hours to overnight, resulting in a 2-3% salt content with condiments and extruding the mix under pressure to produce the
in the fish. The fish are then partially dried on racks. As the brine on the desired product, much like the formation of hamburger patties and
surface dries, dissolved proteins produce a glossy appearance, which is sausages. The formed product may be battered and breaded in a final
one of the commercial criteria for quality. Smoking is carried out in kilns processing step. Other minced flesh products include nuggets and items
or forced-air smokehouses that expose the fish to smoke from smoldering used as hors d’oeuvres, fish chowders, and smoked fish sticks.
wood or sawdust. In cold-smoking the temperature does not exceed 29
°C (85 °F), and the fish is not cooked during the process. Hot-smoking
is more common and is designed to cook the fish as well as to smoke it. เอกสารอ้างอิง/Reference
www.britannica.com
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