COATED FISH FEED PELLETS AND PROCESS FOR MAKING THE SAME.

Technical Field

This invention relates to coated fish feed pellets and to the process for making the same.

Background Art

In the past there has been considerable waste of fish food supplied for feeding fish in rearing tanks and ponds in fish hatcheries and fisheries because of one or more undesirable characteristics of the fish food. When the fish food is supplied in pellet form, the pellets may be so hard as to be unpalatable to the fish and, consequently, rejected by them. On the other hand, the pellets may be so soft or friable that they disintegrate or dissolve so quickly that they become largely unavailable for fish food. Other pellets are so hard and dense that they sink to the bottom of the tank or pond where they are not readily available to the fish. Another disadvantage of prior fish feed pellets is that they deteriorated undesirably quickly, particularly if they were not refrigerated. Other pellets contained less fat or oil than was desirable in order to make them less subject to disintegration. The result of the use of such prior pellets was that a substantial amount of the fish food was unavailable to the fish and such unavailable portion of the fish food served to enrich or fertilize the tanks or ponds so as to promote the growth of algae and aquatic vegetation which is undesirable in rearing tanks or ponds.

Previous attempts have been made to provide a softer pellet which would be more palatable to fish. Such softer texture, however, usually was provided by

increasing the moisture content which increased the problem of disintegration and dissolution of the pellet material and further tended to promote deterioration of the pellet material prior to use and, consequently, shortened the shelf life of the pellets. If the pellets were dispensed in frozen condition for preservation and to deter disintegration, special apparatus was required to distribute the pellets over the water.

Disclosure of the Invention In accordance with the present invention marine life feed pellets are manufactured by mixing settable gels with pellet feed material, or by coating preformed pellets with such settable gel material. Coatings formed by such gels provide firm but soft and flexible consistency. The settable gels may be alginate or guar gum set by an aqueous solution of calcium chloride, or may be gum tragacanth, pectin or gelatin. The resulting pellet is coherent and does not readily disintegrate either in dry form or in water and, while firm, has a surface that is soft and flexible, making the pellet palatable to marine life, is the degree of firmness of the pellet consistency can be varied and to enable the moisture content and/or the oil or fat content to be greater than previously provided without adversely affecting the texture or keeping qualities of the pellet. The pellet, is durable and will not deteriorate appreciably throughout a long period prior to use even though it is not frozen or refrigerated. Such pellets can have different buoyancy characteristics so that they will float instead of sinking, or may sink gradually, or may seek different depths. Pellets having such desirable attributes can be produced economically with consistent characteristics.

Brief Description of the Drawing Figure 1 is an elevation of schematic

equipment that can be used for the production of coated pellets according to the present invention.

Best Mode for Carrying Out the Invention

The body or core of the pellets utilized for the present invention may be composed of conventional fish feed pellet material, as follows:

Weight Protein 80.0% to 95.0% animal protein selected from fish meal herring meal wet fish mix crab meal dried whey dried blood dried blood meal vegetable protein selected from wheat flour wheat middlings wheat germ meal soy flour soy bean meal cottonseed meal corn meal tapioca starch

Oil 5.0% to 20.0% fish oil selected from herring oil menhayden oil Fortifying Ingredients less than 1.0% trace minerals vitamins choline chloride ascorbic acid Binder 0.0% to 4.0% ligninsulfonate Pellets can be made from the foregoing ingredients by a

variety of different pelletizing machines which are commonly used in the feed industry. Such machines may form the pellets by molding them under pressure in mold cavities or by extrusion. The lignosulfonate binder provides cohesiveness for the other materials. In the formation of the pellets, the nonaqueous ingredients are mixed into a dough by the inclusion of from 10 percent to 35 percent of water depending upon the consistency of the pellet desired. The present invention provides a coating for the core pellets composed principally of gel material and gel-setting material although, where a larger proportion of water is used in the formation of the pellet dough, it may be desirable to include some gel material in the bod -dough mixture itself.

The coating may be formed by the interaction of settable gel material and gel-setting material. While the settable gel material could be alginate, pectin, gum tragacanth, guar gum or gelatin, the preferred gel material is sodium alginate. Also, while various gel-setting agents could be used in conjunction with the settable gel material, a preferred gel-setting material is calcium chloride.

The sodium alginate can be mixed with water in the ratio of 2 percent alginate to 98 percent water by weight and this alginate-water mixture is sprayed onto the surface of a preformed pellet, or the preformed pellet is otherwise drenched with the settable gel aqueous liquid. Immediately after the application of the settable gel to the surface of the pellets, gel-setting material is applied to the surface of the pellets such as by a spray. Such spray may be a mixture of 10 percent calcium chloride and 90 percent water by weight. While the coating can consist only of the settable gel and the gel-setting material, such coating can serve as a vehicle for additional oil, such as fish oil. The amount of oil supplied in the coating can be 5

percent to 10 percent of the weight of the pellet. Such oil will serve to plasticize the coating and make it softer. Moreover, the oil may be of different types such as coconut oil, fat or tallow, which can alter the specific gravity of the pellet.

The pellet-coating material may also serve as a vehicle for preservative for the pellet material, such as aldehyde, propylene oxide, ethylene oxide, propylene glycol, propionic acid, sulfur dioxide or carbon dioxide. The aldehyde used should be an edible aldehyde such as vanillin, anisaldehyde or butyraldehyde.

The specific gravity of the coated pellet is approximately 1 and can be adjusted so that the pellet will float or will sink slowly in water of different densities, not only by a judicious selection of the type and quantity of oil included in the body of the pellet and in its coating, but the settable gel and water mixture can be aerated by beating it prior to applying it to the surface of the pellets so that minute air bubbles will be trapped in the coating as it is set by the gel-setting material applied to the surface of the pellets immediately after the settable gel material is applied to increase the buoyancy of the pellet. Specific examples of pellets made in accordance with the present invention are illustrated by the following examples:

Example 1

Weight fish meal 50.0 % wheat flour 9.6 % soy flour 15.0 % dried blood flour 10.0 % fish oil 12.0 % ligninsulfonate 2.0 % trace mineral premix 0.5 % vitamin premix 0.6 % choline chloride 0.225% ascorbic acid 0.075%

-fa- Water in the amount of 10 percent to 25 percent of the foregoing ingredients by weight may be mixed with the pelletizing ingredients to form a dough which may be formed into pellets by being pressed in a mold or by being extruded.

The surfaces of the preformed pellets are sprayed with a settable gel mixture of 1 percent by weight of sodium alginate in warm water. The amount of such settable gel material sprayed onto the surface of the pellets should be approximately 5 percent of the weight of the pellets. Such spraying may be accomplished while the pellets are free-falling or are being transported by a conveyor. Immediately thereafter the pellets are sprayed with gel-setting material which may be 10 percent by weight aqueous solution of calcium chloride. The amount of such gel-setting material sprayed onto the pellets may be approximately 5 percent of the weight of the pellets. Following the two pellet-spraying operations, the pellets may be passed through a drying atmosphere to facilitate setting of the coating.

Example 2 The pelletizing material may consist of the following ingredients: Weight fish meal 20.0 % wheat middlings 37.05 % wheat flour 5.0 % soybean meal 15.0 % dried blood meal • 10.0 % fish oil 10.0 % ligninsulfonate 2.0 % trace mineral premix 0.1 % vitamin premix 0.6 % choline chloride 0.175% ascorbic acid 0.075%

The foregoing pelletizing ingredients, except for the oil, may be mixed with 10 percent to 25 percent of water

into a dough and pellets formed by being pressed in a mold or by being extruded.

The gel coating is formed by mixing 2 percent of sodium alginate with water and spraying such settable gel material onto the surface of the pellets, or otherwise drenching the surfaces of the pellets, using an amount of settable gel material equal to approximately 8 percent of the weight of the pellets. When the coating material on the pellets has thickened, 1 percent by weight of bentonite and 1/2 percent by weight of ammonium hydroxide are blended with the 10 percent of fish oil specified in the pellet material formula. Such mixture is applied to the pellets as a coating over the settable gel material. The pellets are then immediately sprayed with a gel-setting material consisting of a 10 percent by weight solution of calcium chloride in water. An amount of such solution equal to approximately 1 percent by weight of the pellets of such gel-setting material should be applied to the pellets. The pellets may then be subjected to a heated atmosphere to facilitate drying and setting of the coating.

The pellets made according to the procedure of Example 2 have their entire oil content in the coating, which deters solution or dissipation of the pellet material into water surrounding the pellet. Also, the presence of the oil in the coating will plasticize the coating to soften its consistency so as to make it more palatable for fish.

For either type of pellet resulting from Example 1 and Example 2, if the moisture content of the pellet is high, such as 15 percent by weight of water or more, the settable gel coating can incorporate edible aldehyde such as vanillin, anisaldehyde or butyraldehyde. The settable gel coating may, for example, consist of 2 percent by weight of alginate, 18 percent by weight of aldehyde and 60 percent by weight of water. The amount of settable gel material applied to the surface of preformed pellets should be equal to

at least approximately 10 percent to 15 percent of the weight of the uncoated pellets.

An alternative procedure for preserving pellets having a moisture content of 15 percent or more is to coat the pellets with a settable gel coating that does not incorporate aldehyde and then smoke the pellets with smoke from burning grease that contains the aldehyde acrolein.

Example 3 Pellets made from the following ingredients may be particularly suitable for feeding shrimp:

Weight herring meal 29.0 % crab meal 4.0 % wet fish mix 30.0 % dried whey 5.0 % wheat germ meal 4.5 % cottonseed meal 15.0 % corn meal 4.0 % herring oil 6.5 % choline chloride 0.5 % vitamin premix 1.5 %

Pellets may be made from this material by mixing it into a dough by the addition of 10 percent to 25 percent by weight of water. Such pellets may be coated with a settable gel coating in the manner described in connection with Example 1.

Representative equipment for producing and coating pellets includes storage bins a, b, c, etc. having hopper bottoms for the various dry ingredients to be included in the pellet mix. Supply pipes from the several storage bins feed into the common line 2 through which the dry material passes to the ribbon blender 3. Such supply pipes may be screw conveyors. The oil and water components are also supplied to such blender to enable the blender to form the pellet material into a dough.

From the ribbon blender, the dough is transferred by the screw conveyor 4 to a multiple strand extruder 5. One or more knife blades 6 extending radially from a rotating shaft 7 sever the strands extruded from the machine 5 into pellets 8 which fall onto a collecting conveyor 9. During such fall the settable gel material may be sprayed onto the pellets followed by spraying onto them the gel-setting material. Drying and setting of the coating on the pellets can be facilitated by passing the conveyor 9 through a heated drying atmosphere following which the pellets are dumped from the discharge end of the conveyor into a freeze blast air conveyor 10 where the pellets are frozen. From such air conveyor, the pellets are discharged into a bagger 11 which deposits the completed pellets into bags 12 for storage and transportation to the location where the feed is to be used.

During the bagging operation, carbon dioxide or nitrogen can be supplied to the bags so that when they are sealed the pellets will remain in an inert atmosphere to promote preservation until the bags are opened at the location where the feed is to be used.