Food or edible material: processes – compositions – and products – Surface coating of a solid food with a liquid
Utility Patent
1999-06-22
2001-01-02
Sayala, Chhaya D. (Department: 1761)
Food or edible material: processes, compositions, and products
Surface coating of a solid food with a liquid
C426S233000, C426S315000, C426S541000, C426S805000
Utility Patent
active
06168815
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for direct production of dry feed for fish and shell fish (Crustacea) based on fresh fish raw material.
BACKGROUND OF THE INVENTION
Farming of different species of fish and shell fish is today a very expansive line of business which also is expected to grow in many countries. Different species demand different types of feed but common for many species are demands on a high content of fish protein and fish oil. Previously fresh fish or fresh fish waste was used for production of fish feed. The fish or the fish waste was divided into pieces, mixed with different dry additives as cereal products, protein additives as fish meal or blood meal, before the mixture was formed into pellets. The water content of the formed pellets is 40%. A feed with such a high content of water has, however, a limited storage time.
Nowadays the most part of the fish feeds which are found on the market are produced from dry products, where the fish protein is in the form of fish meal. During the production of fish meal fresh fish or fish waste is heated to about 90° in order to liberate water and fish oil. During this heating the proteins are-denatured, which means that the functional qualities deteriorate. After the heating the fish material is separated mechanically in several steps, firstly free water and oil are drained from the fish material in a sieve, after that a further dewatering and defatting is carried through in a screw press. The water from the sieve and the press is clarified in a decanter and the solid phase which is separated in the decanter is added to the press cake.
The water phase from the decanter is divided in a separator into fish oil and stick water. During these process steps the temperature is kept around 90° C. in order to achieve the best possible separation of fat. After the separation the stick water is concentrated by way of evaporation in a fall film evaporator to a dry substance content of 35-40%. The concentrated stick water is mixed with the press cake and the mixture is dried in directly or indirectly heated dryers to a water content of 6-10% water. The total production time up to a finished fish meal is around 3-4 hours and both fish meal and fish oil are subjected to a considerable thermal effect during conventional production.
The fat content in the finished fish meal shall according to international standard be lower than 12%, but often the content is still lower. In order to diminish the thermal effect there is now also so called LT-meal (Low Temperature) for sale. This meal is dried under vacuum at a temperature of 75-80° C.
When producing fish feed from fish meal today different methods are used, where forming of the pellets takes place in a pelleting machine e.g. type California or through heat extrusion where the mass is cooked. The most modern method is forming by extrusion. In both methods one starts with a dry mixture with the desired composition of fish meal and fish oil, alternative protein sources, cereals and vitamins, pigments and other things. If the forming takes place by way of extrusion water is added to this dry feed mixture in order to give a homogeneous composition. Steam is introduced in the mixture in order to force the starch in the cereals to gelatinize. During the following extrusion a high pressure is built up in the product mixture and the temperature increases at the same time to about 120° C. When the product has passed the extruder the pressure is lowered and a part of the water is vaporized at the same time as the formed pellets expand, at which they get a porous structure and may absorb oil. During a subsequent coating with oil the fat content of the feed product may be increased to 20-30% fat. After extrusion the water content is high, 20-30% and the addition of oil is preceded by a warm air drying at temperatures of 50-100° C. The water content of the finished product is below 10%.
When the forming to pellets takes place in the pelleting machine the mixture is rolled through a matrix, a disc with cone shaped openings. The feed mixture is pressed through the openings by the roll with a high pressure and the formed pellet has been pressed together to a strong and solid product. The stability of the pellet depends on how hard it is pressed together. The fat content of the feed mixture may not be too high during the forming since too high an oil content gives a less powerful compressing. As a consequence of the compressing the pellet will be compact, which means that the ability to suck up oil at the following coating will be limited. The maximal fat content at a sufficient mechanical strength of the pellet is about 18%.
According to today's technology one firstly produces a fish meal from the fresh fish raw material. When producing fish meal one usually requires a low fat content in the fish meal. In order to achieve this goal one tries to reduce the amount of oil in the fish raw material during the production of fish meal.
When producing fish feed one desires on the contrary to produce a product with a high fat content and during the production process large amounts of fat are added to compensate for the low fat content in the fish meal.
During the extrusion the feed mixture must have a certain water content in order that this process step may be carried through in an optimal way. The fish meal has earlier been dried to a water content of about 10, which has brought about an impairment of the collodial bonding and nutritional value of the protein. After the extrusion the feed product is dried with temperature effect to a water content of maximally 10%, which also influences the quality of protein.
One aim of the invention is to produce a fish feed directly from fresh fish raw material and avoid the intermediate step which production of fish meals constitutes.
According to WO 96/01058 it is proposed that a fish feed is produced directly from fish material by mixing an intermediate product from the production of fish meal with a concentrate of stick water, forming the mixture to a product at a temperature of 20-120° C., which product then is dried. The feed which is produced according to this publication consists of pure fish.
SUMMARY OF THE INVENTION
According to the invention there is now proposed a method for production of dry feed for fish and shell fish from a fresh fish raw material, which involves a gentle treatment of the raw materials during all process steps up to the produced feed products, but at the same time gives possibilities for adaption to the special demands for different species of fish and shell fish.
The method according to the invention is mainly characterized in that vegetable cooked (already pasted) carbohydrates are added to the fresh fish raw material together with other additives as minerals, vitamins and binding agents during the production to feed to give a carbohydrate content in the produced feed of at least 5%. The water content in the fractions which contain fish proteins are during all process steps up to the forming to feed pellets above 10%, at which the produced dry feed contains 25-60% protein, 10-40% fat and 5-25% carbohydrates and in that the feed contains 25-60% fish protein and up to 40% fish oil. According to the proposed method the production of dry feed takes place in such a way that unnecessary drying steps are avoided which gives a feed product with a high nutritional value. Due to the fact that the said water content never falls below this value the protein remains in colloidal form.
The vegetable carbohydrate products consist of different kinds and amounts of cereals which may be metabolized by the fish species for which the feed is intended.
The proposed method is suitably carried through in such a way that a fish material obtained from fish raw material is heated to such a temperature that pasteurization/sterilization takes place and that the fish material is separated into at least two fractions, liquid and solid phase. The fraction which contains the solid phase is dehydrated during a low thermal effect to a wa
Kossmann Heinrich
Ludvigsen Bent
Alfa Laval AB
Fish & Richardson P.C.
Sayala Chhaya D.
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