Food or edible material: processes – compositions – and products – Surface coated – fluid encapsulated – laminated solid...
Reexamination Certificate
1999-10-29
2001-01-16
Sayala, Chhaya D. (Department: 1761)
Food or edible material: processes, compositions, and products
Surface coated, fluid encapsulated, laminated solid...
C429S103000, C429S472000, C429S472000
Reexamination Certificate
active
06174552
ABSTRACT:
This invention relates to a method of improving the sinkability of fish food pellets.
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, sometimes 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 issue of pellet density at first glance appears to be quite straightforward. If it is assumed that the density of freshwater is 1 g/cm
3
then it seems logical to conclude that any object which has a density of more than 1 g/cm
3
would sink in freshwater. Typically the density of fish food pellets is approximately 1.2 g/cm
3
, so naturally the food should sink in water.
However, the effective density of the fish food pellet may vary. For example, current manufacturing techniques can cause the surface of the pellets to be coarse and have a plurality of small crevices, wherein small pockets of air can be trapped. This gives the pellet a buoyancy that prevents it sinking, leaving it floating on the surface. The overall shape of the pellet may affect its ability to trap air; concave surfaces trap air more readily than convex surfaces.
Also it should be considered that seawater and even freshwater contain some dissolved minerals, which increase the density of the liquid medium. The density of the water can easily be increased by as much as 5%. If it is also considered that typically it is only the average density of the fish food pellets that is 1.2 g/cm
3
and that the density of some of the pellets may be below 1.2 g/cm
3
, then it can be seen that a high salt water content may prevent the food pellet sinking. Further, low temperatures can slightly increase the density of the liquid medium.
Another factor opposing the sinking of the food pellet is the surface tension of the water. It has been found that in cold climates, which are typical of the places around the world where fish are farmed, the surface tension of the water is greater than in warmer climes. The pellet can be held by the surface tension of the water, at or just below the water's surface, and all the problems of floating food pellets are incurred. As the food pellets typically contain lipids, whether plant or animal in origin, the surface of the food pellets can be significantly hydrophobic. This property enhances the effect of the surface tension of the water.
The problem of surface tension can be enhanced by or act in concert with the previously mentioned problem of air pockets on the surface of the pellet. In the initial distribution of the pellet, air pockets that are trapped can mean that the pellet floats near the surface of the water. Once near the surface the pellet can be held by the surface tension of the water, so that even if the pockets of air later dissipate the pellet still floats.
The problem of surface tension can increase if the pellets produced from a certain batch are of poor quality. In this case poor quality means that the pellets are smaller in size or weight, or less dense, than they ought to be. The problems that have been described can be particularly predominant when the pellets produced are smaller in size than they ought to be. In this case the surface area to volume ratio of the pellet is increased disproportionately as are the problems caused by the surface of the pellet.
According to the present invention there is provided a method of improving the sinkability of -fish pellets, comprising providing an aqueous solution of a sugar at the surface of the pellets.
Preferably the sugar solution is provided in a coating at the surface of the pellets. The solution may be included preferably in an amount of 1 to 10 percent, most preferably 2 to 6 percent.
The sugar is preferably sucrose, and an especially effective solution is in the form of molasses or a by product thereof.
The invention also provides fish feed pellets comprising nutrients, the feed pellets having a coating of sugar solution.
Preferably the sugar solution is an aqueous solution comprising between 1 and 10 percent sugar.
Preferably the coating also comprises between 5 and 40 percent oil.
In one particular embodiment the invention comprises a first coating of 15.5% fish oil and a second coating of 2 percent sugar beet condensed by product (CSB).
Embodiments of the present invention will now be described by way of illustration in the following Examples and with reference to the accompanying Figure
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Mann Jason Jasminder
Nissinen Vesa Juhani
Sneddon Scott
Ratner & Prestia
Sayala Chhaya D.
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