Large-Scale, High Density Storage of Larvae

Abstract

The present invention provides a method for storing insect larvae by means of a storage means. The insect larvae are stored in a cooling medium, e.g. water, in the storage means. The amount of water in the larvae-water mixture in the storage means is controlled to be between 30% and 80%. The content of the storage means is maintained at a temperature below 15 C. The content of the storage means is agitated using agitating means included in the storage means.

Claims

1. A method for storing insect larvae in water by means of a storage means, comprising providing a mixture of insect larvae and a cooling medium to the storage means, controlling the amount of cooling medium in the content of the storage means to be between 30% and 80% by weight, maintaining the content of the storage means at a temperature below 15 C., and agitating the content of the storage means by agitating means included in the storage means.

2. The method according to claim 1, wherein the cooling medium is water.

3. The method according to claim 1, wherein the temperature inside the storage means is maintained below 10 C., preferably 7 C.

4. The method according to claim 1, wherein the temperature inside the storage means is controlled by providing a continuous flow of cooling medium at the desired temperature through the storage means.

5. The method according to claim 1, wherein the temperature inside the storage means is controlled by cooling the storage means using cooling means included in the storage means.

6. The method according to claim 1, wherein a continuous air flow inside the storage means is provided.

7. The method according claim 1, further comprising draining the mixture of insect larvae and cooling medium from the storage means.

8. The method according to claim 7, further comprising separating the larvae from the cooling medium and processing of the insect larvae.

9. The method according to claim 1, wherein the agitation is performed continuously, periodically or in an irregular manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The features, objects and advantages of the invention will be made apparent by the detailed description that follows and the figures wherein

[0022] FIG. 1 schematically shows a storage tank according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Insect larvae may be stored in tanks together with water. In recent years much thought has been put into storing insect larvae in large quantities for a long time period (up to 4 days) without degeneration and while maximising the output. However, there are a lot of problems to be faced when storing the insect larvae. For example, the enzymes in the larvae gut have to be kept from destroying the larvae itself when they die. Therefore, the system must either inactivate the enzymes or keep the larvae alive in such a way that they can control the enzymes.

[0024] A further problem that can occur is the contamination of the larvae by microbial pathogens since the bacteria might be harmful to the larvae. Also, high densities of stored larvae should be avoided since high density or clustering of larvae can result in large heat production which needs to be controlled to prolong the storing period, and further it might lead to crushing of the larvae due to their own weight.

[0025] Furthermore, the larvae should be metabolically deactivated. Otherwise they can develop or require food which might lead to cannibalism amongst themselves. Also, a large storing facility should be used in order to allow for buffering and therefore to have a continuous stream for processing.

[0026] According to the present invention, these problems can be solved by maintaining a homogenous distribution of insect larvae in the water-larvae mixture on the one hand and by maintaining a certain temperature on the other hand. According to the present invention, the water-insect larvae mixture is stirred and cooled to avoid clustering and to reduce the temperature of the insect larvae.

[0027] To achieve the above stated objects, a storage tank is provided. FIG. 1 shows an embodiment of a storage tank according to the present invention. Tank 1 is provided with a water inlet 10, an insect larvae inlet 15, a water and insect larvae drainage 20. The storage tank according to the invention is further provided with an agitation mechanism 50 driven by a motor 51 to stir the content thereof. In the embodiment shown in FIG. 1, separate inlets for water and larvae are provided. According to an alternative embodiment, a water-larvae mixture with the desired ratio may be prepared outside the tank and introduced into the tank via a single inlet. Similarly, separate outlets for larvae and water may be provided. In this case, the water outlet should be equipped with a separating means to ensure that no larvae leave the tank through the water discharge opening. The separating means can be e.g. a grid or any other kind of filtering means which may also be removable. The larvae, on the other hand, may be extracted together with a corresponding amount of water. After extraction, the larvae must be homogenized to prevent clogging of the pipes as they are sent to processing.

[0028] Water provided through the water inlet 10 is mixed with insect larvae provided through the insect larvae inlet 15 inside the storage tank 1. Thereby, the insect larvae are cooled to a temperature according to the water temperature. FIG. 1 shows cooling means 40 arranged at the outer surface of the storing tank that may be used to cool the content of the tank. In order to maintain the temperature of water-larvae mixture inside the tank, a continuous stream of cooled water at the desired temperature may flow through the tank. When maintaining the water at a temperature below 15 C., the insect larvae are not metabolically active and therefore do not require food and evade the problems as explained above. Thus, by maintaining a temperature below 15 C., degradation of the insect larvae can largely be prevented. By maintaining a temperature below 7 C., additionally growth of microbial pathogens is hindered. A preferred ratio of water to insect larvae (by weight) is between 30:70 to 80:20, in other words the amount of water in the mixture shall be 30-80% of the total weight. More preferably, an amount of 50% water and 50% insect larvae by weight is maintained.

[0029] As a further advantage, by storing the insect larvae in water, the effective weight thereof is reduced since they float, and crushing of the larvae due to high densities can thus be avoided.

[0030] If insect larvae begin to cluster, hot spots might arise since the core of a larvae group might stay warm which would counteract the aim of prolonging the storing period. In order to prevent the insect larvae from clogging and developing clusters that are more difficult to fully cool, an agitating mechanism 50 stirs the water-insect larvae mixture without damaging or harming the insect larvae. Once the insect larvae are completely cooled and metabolically deactivated, they cease to produce heat and agitation of the water-insect larvae mixture becomes redundant.

[0031] A further advantage of generating a homogenous mixture of water and insect larvae is that the insect larvae are much easier to extract. Specifically, in the embodiment shown in FIG. 1, the water-larvae mixture is extracted from the tank through piping 20 to outlet 30 towards downstream processing.

[0032] The storage tank is preferably large in order to be able to buffer insect larvae and build up a sufficient quantity of larvae to have a continuous stream for processing. The storage tank preferably is aligned vertically to minimise the necessary floor space but may be aligned horizontally, e.g. for transportation on a truck or the like.

[0033] The present invention allows for large scale, high density storage of insect larvae. Homogenization of the larvae allows avoiding hot spots by clustering of larvae. This also ensures the homogenous outtake of larvae towards the downstream process.