Minced Fish

Dwindling supplies of traditional fish stocks, restrictions on harvesting, increased operational costs and concerns over waste disposal and pollution have contributed to an increased interest in achieving maximum use of fisheries resources. Coupling these factors to a consumer demand for convenient and flavourful, ready-to-eat or heat-and-serve foods offers possibilities for seafood processors to diversify into the production of intermediate products such as minced fish and surimi (washed mince that has been blended with stabilizing ingredients), or formulated foods such as fish nuggets, chowders and various seafood entr?es.

High quality mince, which is essentially free of bones, skin and extraneous material, may be used in a wide variety of value-added products. Lightly coloured mince containing less than 1% fat generally commands the highest price because of its suitability as an ingredient in a broad range of food products. Nevertheless, acceptable minces can be prepared from dark- fleshed, fatty fish and cooked shellfish including whole rock crab and lobster bodies. Usually these latter types of specialty minces are made for specific end-products and may not be marketed as readily as conventional lean, white-fleshed fish mince.

Research associate, Kathy Spencer prepares silver hake surimi in the CIFT pilot plant

Typical yields of mince from small fish average 22% for capelin, 30% for silver hake and 40- 45% for herring and flounder. For larger species such as cod and hake, filleting generally yields 23-35% product, whereas mechanical separation can recover 40-55% minced fish.

Fillet trimmings, headless fish frames, frames with the main portion of the backbone removed, napes and split heads may be used for mince production. Deboning of headless frames can yield 45-65% fish meal. Varying amounts of labour would be required to prepare different types of raw material. Preparation may be conducted as part of a filleting operation or as an isolated procedure at a different location.

Colour, odour, flavour, texture and functional properties such as gel-forming, water-binding and fat emulsifying characteristics are important criteria used to assess mince quality. As with all seafoods, proper handling of the source material, adequate sanitation, efficient processing, and appropriate packaging and storage are required in order to produce high quality products. Mixed species should not be processed simultaneously unless it is known that no adverse interactions will result. Research has shown that mixing hake flesh with flounder or cod mince causes increased toughening and significantly reduces frozen shelf life.

Minces prepared from various species and components of waste will differ in fat protein moisture content, sensory characteristics, appearance and impurities (pieces of skin, bone, spinal cord and fin material). Frames from gutted fish will product a whiter, more stable mince than those from non-gutted fish. Enzymes and blood from the gut and kidney material tend to promote discolouration and accelerate deterioration. Backbone and head material usually produces low quality minces.

The choice and operation of equipment greatly influence the quality, yield and textural characteristics of mince fish. Product can range from a course mince to a fine paste depending on the source material, machine type and setting, and processing method. Baader and Bibun meat separators operate on a belt-drum principle whereby the fish is forced against a perforated drum (hole sizes can range from 1 to 10 mm in diameter). The flesh passes through the holes while the skin and bones are ejected through a discharge chute. Paoli machines break up the bones or shell and separate the flesh by a micro-groove principle, while Beehive machines use a feed-screw or auger and perforated drum to separate pre-chopped material. Using a high belt tension and large-hole drum generally maximizes product yield, as well as the amount and size of impurities. Following deboning, mince may be refined by passing it through a strainer which will remove bone fragments and small pieces of belly lining. The hole sizes in strainers typically range from less than 1 to 2 mm in diameter. Straining coarse minces will reduce the meat particle-size and produce a more homogeneous, pasty product. Blood and enzymes may be extracted by washing the mince, but this process increases the moisture content and may alter the product?tional properties.

Source material for the production of mince should be handled as if it were fresh fish, that is, rapidly chilled or adequately iced and held under chilled conditions until processed. Frozen mince should be stored at -30 ºC in order to maintain high quality. Under good conditions storage life is approximately six months.

For additional information of this and other food quality and safety related topics please contact the seafood specialists at CIFT.