SINKABLE FISH FOOD PELLETS HAVING GOOD PALATABLE PROPERTIES

Abstract: A fish food pellet comprising at least one or more fish nutrients, one or more anti-floating agents, and one or more taste enhancers is described. Such fish food pellets give excellent results with respect to both sinkability and palatability. They minimise the loss of the fish food and provide an enhanced fish growth rate. In one embodiment, the anti-floating and taste enhancer are provided as a top coating on the surface of fish food pellets.

Description: "Sinkable fish food pellets having good palatable properties" This invention relates to sinkable fish food pellets having good fish palatable properties and to a method for feeding fish which minimise the loss of the fish food together with providing an enhanced fish growth rate. Certain types of fish, such as salmon, are now farmed for human consumption rather than caught solely by conventional fishing techniques. The farms include netted or otherwise segregated enclosures, which can be freshwater or seawater, and which contain the fish. The food for the fish is supplied by the fish farmer, most of the time in the form of pellets, which are regularly distributed into the enclosures. Difficulties can arise when the fish food pellets float on the surface of the water for an appreciable amount of time, instead of sinking under the surface where they are then consumed by the fish. The floating pellets can be problematical for several reasons. Firstly the floating pellets can be carried away by water currents, causing the farmer to have to use more food than is necessary to feed the fish. Secondly, not all fish are surface feeders and they may not take food from the surface of the water. Thirdly the floating food may attract other opportunist feeders such as seagulls; not only can this result in loss of the fish food but also the presence of the birds can scare the fish. The two main causes of floating are water surface tension and pellet density. It has been thought for a long time that floating can be attributed solely to pellet density but more recently it has become clear that surface tension is also a major issue. The food pellets typically contain lipids, whether plant or animal in origin, and therefore the surface of the food pellets can be significantly hydrophobic. This property enhances the effect of the surface tension of the water. It has been therefore proposed to add anti-floating agent, like molasses or surfactant to the fish food pellets in order to provide a good sinkability. However the sinkable fish food pellets that have been achieved have shown low palatability with fish. Surprisingly, it has been found that combining an anti- floating agent with a hydrophilic taste enhancer in fish food pellets gives excellent results with respect to both sinkability and palatability. It is therefore an object of the invention to provide a method to feed fish which minimise the loss of the fish food and provide an enhanced fish growth rate. It is a further object of the invention to provide fish food pellets which show enhanced sinkability and fish palatability. Accordingly it is provided a method to feed fish which comprises the step of providing fish food pellets which include, together with a fish nutrient, an anti- floating agent and a taste enhancer. According to the present invention it is also provided fish food pellets comprising a fish nutrient, at least one anti-floating agent, and at least one taste enhancer. Preferably, the anti-floating agent is a surfactant. More preferably, the surfactant is one or more of a) Glycerol polyethylene Glycol nicinoleate, b) Glycenyl polyethylene Glycol nicinoleate, and c) polyoxyethylene sorbitan monoleate. Most preferably, the surfactant is polyoxyethylene 20 sorbitan monoleate sold under the trade mark TWEEN 80 by ICI Ltd. Preferably, the amount of anti-floating agent contained by the fish pellets may vary between 0.05 to 5%, most preferably about 0.2 and 2 % by total weight. It is also preferred that the taste enhancer included in the fish food pellets be a hydrolysed and purified protein concentrate from the sugar beet production and sold under the Trade Mark "Aminofin" by Finnsugar Bioproducts. The amount of Aminofin is preferably ranging from 0.1 to 2%, most preferably from 0.3 to 0.5% by total weight. Another preferred taste enhancer is hydrolysed fish protein concentrate of the type sold by Sopropeche under the name CPSP90. The amount is same as for Aminofin. It is also preferred that the combination of anti- floating and taste enhancer be provided as a top coating on the surface of fish food pellets. Embodiments of the present invention will now be described by way of illustration in the following Examples. In these examples fish pellets according to the invention have been manufactured by extrusion and a coating of fish oil applied under vacuum. These methods are currently used and known in the art. This was followed by a top coating of the anti-floating agent, taste enhancer and a small amount of fish oil onto the pellets under atmospheric pressure. It has been found advantageous to add a small amount of fish oil as the latter acts as a carrier for the anti- floating agent and taste enhancer, to ensure homogeneous distribution. The fish oil used as a nutrient in these examples is non-winterised fish oil. These examples also use polyoxyethylene 20 sorbitan monoleate, sold under the name Tween 30 by ICI Ltd, as the anti-floating agent. Example 1: Influence of the combination of a floating agent and a taste enhancer upon fish food pellets sinkability. 2.5 mm dry pellets from Ewos Norway were vacuum coated with 15% fish oil followed by top coating with a mixture of 0.5% of Tween 80, 0.5% of Aminofin and 1% of total weight non-winterised fish oil. The sinkability of these pellets was compared with the sinkability of the pellets provided with a coating of different anti- floating agents, as control. Thus, some of these were coated with respectively 2% and 4% of CSB (Condensed separator By-Product) molasses. CSB molasses is a by- product from beet molasses production having the following characteristics: Dry matter : about 70% Moisture : about 30% Protein* : about 17% Ash* : about 23% Invert sugars* : about 20% Viscosity cP : about 3000 *: percentage on dry matter basis. Other feed pellets were coated with a mixture of 0.5% Tween 80 and 1% non-winterised fish oil. The data for the time taken for the coated pellets to sink is shown in the accompanying Graph 1. Graph 1 : The graph shows the time taken in seconds for each 2.5 mm pellet to sink in water with 5% salinity (NaCl) , and of a temperature of about 2-3 °C. As can be seen from this graph, the pellets according to the invention and coated with a mixture of anti- floating agent and hydrophilic taste enhancer present an unexpectedly better sinkability with respect to pellets coated with the anti-floating agents alone. Example 2: Influence of the combination of a floating agent and a taste enhancer upon fish food pellet palatability. Fish food pellets were prepared using commercial 2.5mm dry pellets from Ewos Norway which were vacuum coated with 15% fish oil and then divided into three samples. One of them was top coated with 1% "Tween 80". Another was top coated with 1% "Tween 80" and 0.5% "Aminofin", accordingly to the invention. The third one was not top coated, as a control. Three different batches of young Salmon were then prepared and weighed. Each batch was regularly fed during 58 days with one of the different kinds of the above described food pellets. The fish were weighed twice during the trial. The results of the trial are compiled in following Table 1. Table 1 * : Significant difference at 95% probability within single standard deviation, a, b : figures with single letters are statistically significantly different from each other according to the '*' criterion, ns : not significant re standard deviation. As can be seen from the above Table 1, the standard growth rate of salmon fed with the food pellets of the invention (feed number 242) is better than the growth rate with the control pellets (240) and significantly better than the growth rate with the pellets coated with the anti-floating agent alone (241) . Also, the Feed Conversion Ratio (FCR) , which is the total amount of feed used divided by total fish weight gain, (and the inverse of the Standard growth rate) is significantly better with the pellets according to the invention than with both the control and the pellets coated only with anti-floating agent. It will be also noted that the results obtained with the pellets coated without a taste enhancer but with an anti-floating agent (feed number 241) are worse than the control. This test demonstrated the greatly enhanced palatability and efficiency on the fish growth of the pellets of the invention with respect to known fish food pellets. Even if pellets coated with anti-floating agent and taste-enhancer are preferred it should be noted that the invention is not restricted as this preferred embodiment. For example, the anti-floating agent and the taste enhancer can be simply mixed together with the feed components to form the final feed. Effect of different top coatings on sinkability of 2.5 mm pellets 2 % CSB 4 % CSB 0.5 % Tween 0.5 % Tween 80 80 + 0.5% Aminofin

Claims: 9 CLAIMS 1. A fish food pellet comprising at least one or more fish nutrients, one or more anti-floating agents, and one or more taste enhancers. 2. A fish food pellet as claimed in Claim 1 wherein the anti-floating agent is one of the group comprising a) Glycerol polyethylene Glycol nicinoleate, b) Glycenyl polyethylene Glycol nicinoleate, and c) polyoxyethylene sorbitan monoleate. 3. A fish food pellet as claimed in Claim 2 wherein the anti-floating agent is polyoxyethylene 20 sorbitan monoleate. 4. A fish food pellet as claimed in any one of Claims 1 to 3 wherein the amount of anti-floating agent in the fish pellet is between 0.05% to 5% by total weight. 5. A fish food pellet as claimed in Claim 4 wherein the amount of anti-floating agent in the fish pellet is between 0.2% and 2% by total weight. 6. A. fish food pellet as claimed in any one of Claims 1 to 5 wherein the taste enhancer is a protein concentrate. 7. A fish food pellet as claimed in Claim 6 wherein the taste enhancer is Aminofin or CPSP90. 8. A fish food pellet as claimed in any one of the preceding claims in which the amount of taste enhancer in the fish pellet is between 0.1% to 2% 10 by total weight. 9. A fish food pellet as claimed in Claim 8 wherein the amount of taste enhancer in the fish pellet is between 0.3% to 0.5% by total weight. 10. A fish food pellet as claimed in any one of the preceding claims wherein the anti-floating agent and the taste enhancer is, or is included in, a top coating on the surface of a fish nutrient core. 11. A fish food pellet as claimed in any of Claims 1 to 9 wherein the anti-floating agent and the taste enhancer is homogeneous with the or each fish nutrient. 12. A fish food pellet as claimed in any one of the preceding Claims wherein the fish nutrient is fish oil. 13. A fish food pellet as claimed in any one of the preceding claims using a dry pellet core. 14. A process for preparing a fish feed pellet including one or more fish nutrients, one or more anti-floating agents, and one or more taste enhancers, wherein the or each fish nutrient, anti-floating agent and taste enhancer are admixed together. 15. A process as claimed in Claim 14 wherein the or each fish nutrient, anti-floating agent and taste enhancer are homogeneously mixed together. 16. A process as claimed in Claim 14 wherein the or 11 each anti-floating agent and the or each taste enhancer are added as a, or as part of a, top coating. 17. A process as claimed in Claim 16 wherein the top coating includes fish oil. 18. A fish process as claimed in Claim 16 or Claim 17 wherein the or each fish nutrient is coated around the pellet core prior to the top coating of anti- floating agent and taste enhancer. 19. A fish food pellet comprising at least one or more fish nutrients, one or more anti-floating agents, and one or more taste enhancers whenever prepared by a process as claimed in any one of Claims 14 to 18. 20. Use of a fish feed pellet as claimed in any one of Claims 1 to 13 and 19 to feed fish.

Inventors: MANN JASON JASMINDER, NISSINEN VESA JUHANI, SNEDDON SCOTT, MANN, JASON, JASMINDER, NISSINEN, VESA, JUHANI, SNEDDON, SCOTT
Applicants: EWOS LTD, MANN JASON JASMINDER, NISSINEN VESA JUHANI, SNEDDON SCOTT, EWOS LIMITED, MANN, JASON, JASMINDER, NISSINEN, VESA, JUHANI, SNEDDON, SCOTT
Application year: 1998
Main classification: A23K1
IPC codes: A23K1