Fodder and method for production of fodder containing lipids of low melting temperature, in particular fodder for aquatic organisms

A fodder contains lipids having a low melting point, especially a fodder for aquatic organisms, wherein the lipids are carried within a crystalline structure formed by other lipids, emulsifiers or a mixture of lipids and emulsifiers. A method for making said fodder, wherein into the lipids firstly is mixed an additive component cooperating with the lipids, and forming a mixture which is at least partly crystalized at the fodder's highest temperature of use and storage. The mixture is added at elevated temperature to porous pellets, and the subsequent cooling brings the mixture into a crystalized state.

The invention relates to a fodder containing lipides having a low melting 
temperature, particularly a fodder for aquatic organisms, and a method for 
making such a fodder. 
Fodder for aquatic organisms such as e.g. fish, is to contain energy, 
micronutrients and proteins in a proportion varying from species to 
species. It has been found that salmonids needs a fodder relatively rich 
on energy. Energy may come from proteins, lipides and hydrocarbons, but 
lipids are preferred both with regard to nutrition and with regard to 
fodder economy. 
In order to achieve a fodder having a combination of lipides and proteins 
giving good growth, having the lowest possible raw material price as well 
as the desired physical properties such as e.g. low sinking speed in 
water, liquid lipides are supplied to a dry, porous pellet. The lipides 
are absorbed and kept in the pores of the pellet. 
Marine oils have been found to be nutritional favourable. The ordinarily 
used oils are liquid at normal ambient temperature. Oils leaks out from 
the pores, and the leakage increases with temperature. The nutritional 
value is reduced and at the same time, the oil both pollutes and can cause 
feeding equipment and other farm equipment to malfunction. Leakage of oil 
may appear even In the manufacturing process and is, thus, also a 
disadvantage for the feed producer. 
Recently, there has been a development towards increasingly more lipid-rich 
fodder for salmonids. Leakage of oil restricts the amount of lipid having 
a low melting temperature that the fodder can contain, and this fact has 
restrained the product development in the field in question. How much oil 
a pellet can hold depends primarily on the porosity, the nature of the oil 
and the ambient temperature. 
In order to be capable of using the preferred marine oils having a low 
melting point, the fodder producers have taken several measures in order 
to prevent leakage. One approach has been to try various solid materials 
in order to improve the structure and porosity of the dry pellet, thus 
increasing the ability to absorb oil. The addition of oil has been tried 
at various stages in the production process, and the production equipment 
has been modified. Also a thickener such as lecithin has been added the 
oil. Up to now, none of these measures have reduced leakage of oil to an 
acceptable level, while still maintaining important fodder properties such 
as taste, nutritious value and digestibility. 
The object of the invention is to provide a fodder containing lipides 
having a low melting point, at the same time reducing the risk for 
leakage. Also, an further objective is to provide a method for making such 
a fodder. 
The objectives are achieved through features as defined in the following 
claims.

In the following, the invention is firstly described in general, and then 
through three embodiments. 
The main principle of the invention is related to the fact that lipides 
which have a low melting point, i.e. in the form of an oil, are bound in a 
crystalline structure formed upon the addition of an additive component of 
lipid nature, and which normally has a higher melting temperature than the 
oil. 
The crystalline structure is stable at temperatures above the normal use 
and storage temperature of the fodder. The additive+oil is applied in a 
liquid state at elevated temperature to porous pellets and, following 
cooling, the crystalized mixture stays, as well demonstrated, within pores 
in the pellets, but in a solid or jelly-like form. Experiments have shown 
that lipids having a melting point above fifty degrees Celcius and 
containg more than five percent fatty acids having twenty carbon atoms or 
more, are well suited to function as the additive component. Also, good 
results have been achieved with mono- and di-glyceride emulsifiers, as 
well as tri- glyceride. 
Lipides having a lower melting point remain liquid within the crystalline 
structure, but it is assumed that a portion of these lipides are included 
in the crystalline structure as well. Provided that the additive component 
forms a crystalline structure capable of accommodating the actual lipides, 
the mixture appears in a solid or jelly-like form at relatively high 
ambient temperature. In order for the mixture to penetrate well into the 
porous pellet, it may be necessary to keep both the mixture and the pellet 
at an elevated temperature for a period. Additive components containing 
mono-, di-, tri-glyceride seem to give an improved penetration into the 
pores. 
That a crystalized additive component can serve as a carrier for liquid 
lipides, may be explained by the fact that the additive component forms a 
crystalline structure consisting of many small crystals rather than a few 
and large crystals, thus forming many microscopic crystal boundaries with 
spaces for liquid lipides. 
The ability of a crystalized additive component to hold on to oil at a 
given temperature can be measured by keeping a mixture of oil and additive 
component in a measuring glass at the actual temperature. A crystalized 
sediment is formed, carrying a larger or smaller part of the oil, and free 
oil becomes floating on top of the sediment. After e.g. one day, the level 
of the sediment, called the crystallization height, and the total height 
to the liquid surface is read. The proportion between the two 
levels/heights is a measure of the ability of the additive component to 
hold on to oil at the actual temperature. Experiments have shown that in 
order to achieve a satisfactory binding of oil within the fodder, the 
additive component--at the fodder's highest storage or use 
temperature--should give a crystallization height (level) corresponding to 
at least half the total height, when measured as described. 
The table below represents measurements of achieved percentage 
crystallization height with varying concentrations of different additive 
components in a marine oil at a temperature of forty degrees Celsius. 
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Concentration in percent 
Additive component 
1-2 2-3 3-4 4-5 6-7 8 
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Tempered rape seed oil (A) 
25 75 -- 85 -- 95 
Mono-glyceride (B) 
-- -- 65 -- 95 -- 
Mono-di-glyceride (C) 
-- 50 -- 95 -- -- 
Mixture A + B 45 65 95 95 100 -- 
Mixture A + C 50 40 60 100 95 -- 
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In the table, three additive components are indicated by name and, 
additionally, denoted through a capital letter A, B and C. Also, 
measurements from experiments using mixtures of the additive components A 
and B as well as A and C are recorded. The table shows that a satisfactory 
binding of oil is achieved, i.e. corresponding to approximately fifty 
percent crystallization height, when two to four percent of the shown 
additive components are added into the oil. 
In a first example of embodiment of the invention, melted, fully tempered 
rape seed oil having a melting point of about sixty degrees Celsius is 
added to marine fish oil. This corresponds to additive component A in the 
table. Thus, the additive component as well as the marine oil are lipides. 
The liquid mixture of tempered rape seed oil and marine fish oil are 
applied to, and absorbed by, the dry pellet at elevated temperature, so 
that crystallization does not start before the mixture is absorbed. The 
capelin oil should have a temperature of at least forty degrees Celsius, 
in order to achieve a homogenous mixture and in order to avoid that the 
rape seed oil crystalizes immediately. Crystallization occurs at twenty 
five to thirty five degrees Celsius, dependent on the cooling speed and 
the percentage amount of rape seed oil added. 
In a second example of embodiment, a mono-glyceride of a saturated 
vegetable oil was used, the oil having a melting point of about seventy 
two degrees Celsius. When adding three percent mono-glyceride into marine 
fish oil, more than fifty percent crystallization height is achieved, such 
as indicated for additive component B in the table. The mixture is 
supplied to the porous pellet at elevated temperature as described above. 
As a third example of embodiment, it should be mentioned that a 
mono-di-glyceride lacking a defined melting point and containing about 
fifty percent mono-glyceride of a vegetable oil, crystalizes together with 
capelin oil and gives satisfactory crystallization height when the 
concentration exceed three percent, such as indicated in the table for 
additive component C. Also this mixture is added to the porous pellet at 
elevated temperature. 
In other respects, experiments have shown that a mixture of tempered rape 
seed oil and mono-di- and/or tri-glyceride functions well a crystalizing 
additive components in capelin oil, such as indicated for the mixtures A+B 
and A+C in the table. When mixing mono-, di-, tri-glyceride into the 
tempered rape oil, the amount of the latter may be reduced, effecting a 
better penetration into porous pellets. Additionally, some improvement in 
the digestibility of the fodder may be expected. No substantial loss of 
nutritional value, digestibility or palatability of fish fodder made in 
accordance with the invention has been found, where as leakage and loss of 
lipides have been greatly reduced.