Food or edible material: processes – compositions – and products – Treatment of live animal
Reexamination Certificate
2002-06-04
2003-03-04
Sayala, Chhaya D. (Department: 1761)
Food or edible material: processes, compositions, and products
Treatment of live animal
C426S442000, C426S657000, C426S805000
Reexamination Certificate
active
06528100
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for the modification of protein structure in finish shaped feed pellets, balls or the like, among other reasons in order to contribute to strengthening the permanence of the pellet shape in granular feeds of this sort. The invention also relates to feedstuff manufactured according to this method for the formation of a shape-permanent feed in pellet form.
Many types of animals in breeding, e.g. salmon and trout, are carnivorous (meat-eating). Their natural food consists of insects (for salmon and trout in the freshwater phase), fish and crustaceans. For other carnivorous farmed animals, such as mink and foxes, the feed may also contain the mammalian flesh, for example fresh slaughterhouse waste. Insects and crustaceans have an exoskeleton which i.e. consists of chitin. Chitin is a linear polysaccharide of N-acetyl-D-glucosamine linked by &bgr;1→4 bonds. Other structural carbohydrates such as cellulose (&bgr;[1→4]D-glycose) and alginate (D-mannuronic acid) are not found in these prey animals, nor do they contain starch (á[1>4]D-glycose) as energy stores. Nevertheless, salmon, trout and other carnivorous fish and animals have enzymes (for example, amylase) that are capable of breaking down starch in the gut and making it digestible, but they may be less efficient in this respect than herbivorous (plant-eating) fish and animals.
In feeds intended for carnivorous fish it is usual to add between 8% and 25% carbohydrates, for example in the form of wheat or maize, as a binding agent. After pressing, but especially after extrusion, the starch in these carbohydrates will form a matrix or base mass which gives the pellets mechanical strength and shape permanance so that the shape of the pellets can be maintained after drying, further processing, storage and transport.
Carbohydrates are utilised in metabolism as a source of energy. The energy density of carbohydrates is lower than that of protein and fat (17.6; 23.9 and 39.8 MJ/kg respectively). The digestibility of carbohydrates is also lower in carnivorous fish, and declines as the proportion of complex carbohydrates in the feed (above 10%) increases. Experiments have shown that salmonids have no metabolic need for carbohydrates. If fat replaces carbohydrates as an energy source, a carbohydrate-free fish feed of this sort will contain more energy per unit weight, as long as the relative proportions of the other components are held constant.
In order to give feed pellets shape permanence and mechanical strength, as mentioned above, it is known to add a binding agent in the form of 8%-25% carbohydrates, for example wheat and/or maize. After pressing or extrusion in the feedstuff material there will be established a starch matrix of the desired strength.
Other techniques in connection with the forming of feed into pellets balls or the like, have also been described. According to U.S. Pat. No. 4,935,250, for example, a gel or mass of alginate is also produced during the forming.
The patent literature includes descriptions of feeds and feed mixtures in which the mass consists of gelatine or caseinate. See, for example, British Patent No. 2,217,175.
There are also feeds in which the binding characteristics produced by the coagulation of native proteins are exploited; see NO 179 731.
Small feed particles can be produced with the aid of an agglomeration technique, which are based on the principle of aggregating extremely small particles into larger particles. This process does not utilize carbohydrates as a binding agent. The feed components are bound together through various forms of contact bonds between the solid particles in the feed. The different forms of contact bonds can vary from hydrogen bonds, adhesion and cohesion to capillary forces. New covalent bonds are not created in this process. This is an obvious disadvantage for the maintenance of the feed pellet's form and strength, because covalent bonds are stronger than other chemical bonds.
A serious disadvantage of agglomerated feeds is thus that the bonds are weak, and given the lack of a continuous matrix such pellets are friable and fragile. The agglomeration technique cannot be utilised to produce particles of feed in pellet form with a diameter larger than about 2.5-3.0 mm.
In order to be able to produce larger feed particles/fragments/pellets/balls, etc., we must abandon the agglomeration technique without addition of carbohydrate and again return to carbohydrate as a binding agent. In low concentrations, complex carbohydrates such as starch are digested by salmonids, for example, but if their concentration exceeds 10% the digestibility of the carbohydrate fraction decreases (Aksnes A., 1995. Growth, feed efficiency and slaughter quality of salmon, Salmo salar L., given feeds with different ratios of carbohydrate and protein. Aquaculture Nutrition, 1:241-248).
GENERAL DESCRIPTION OF THE INVENTION
The energy content of the carbohydrate fraction may be replaced by fat within the feed recipe. This will result in greater freedom with respect to varying the relative proportions of fat, protein and micronutrients since the carbohydrates make up the remainder of the feed recipe. Such a feed will be richer in energy than an equivalent feed containing carbohydrates, and a reduction in the feed conversion ratio, defined as the quantity of feed consumed to produce one kilo of fish biomass, will be obtained.
In accordance with the present invention one has aimed at showing a method of modifying the protein structure of feeds whose nutrient composition closely resembles the natural choice of foods of carnivorous fish and animals. According to the invention, favourable binding is obtained in feeds—without carbohydrates—resulting in shape permanence in pellets and similar forms of feedstuff, and in such a way that the maximum particle size/pellet diameter can be increased in the case of agglomerated feed while maintaining the shape of the feed. The invention also aims to increase the energy density of all types of feed, particularly fish feeds.
The above-identified objective is reached by proceeding as described herein. A feedstuff that has been treated as described in accordance with this method and which is intended for the forming of pellets or the like, and properties relating thereto are identified herein. Feed pellets made of such a feedstuff, whose protein structure has been modified by the method, are also disclosed herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The method and product formed by the method thus consists mainly of a feedstuff, or alternatively of one or more of the components of which it consists, for forming pellets, alternatively of coating the surface of the formed pellets, in order to add an enzyme (preferably transglutaminase) that function as a catalyst for the formation of covalent bonds between the amino acids which make up the protein chains in protein raw materials containing proteins in native or denatured form. The raw materials of the protein in the feed mixture include the natural amino acids glutamine and lysine in the protein chains. The added enzyme will act as a catalyst and catalyze the formation of covalent (å-(&ggr;-Glu)Lys) bonds between the amino acids glutamine and lysine in the protein raw ingredients in the feed.
Through the adoption of reaction temperature and reaction time this enzymatic reaction will form a matrix or basic mass of protein raw materials which will exhibit adequate strength to give feed pellets a constant and lasting shape.
In agglomerated feed this enzymatic reaction will lead to covalent transverse bonds (cross-bonds) between the proteins. This will give the agglomerate increased strength by introducing the strongest type of chemical bond in addition to the other three types of chemical bonds which provide the feed product with firmness and strength.
In pressed or extruded feeds, the formation of covalent (å-(&ggr;-Glu)Lys) bonds that lead to the formation of a protein matrix will be able to partially or who
Hoff Kjell Arne
Thorsen Fred Hirth
Nutreco Aquaculture Research Centre AS
Sayala Chhaya D.
Vidas Arrett & Steinkraus P.A.
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