From Offal to profit

Worldwide demand for fish products in fillet form, such as salmon is increasing steadily and that means the number of fish farms and fish processing plants is on the up too. Simultaneously the cost of disposing of by-products has grown tremendously.

Yet by-products should be considered as raw material for high-grade oils rather than as waste. To get the best prices, high quality standards for raw material and processing equipment are necessary. Obviously, using fresh by-products right after gutting gives high final product quality. Just as important is very careful treatment of these by-products in order to maintain quality throughout processing.

"We believe the FLOTTWEG TRICANTER® Process, in combination with the loop coagulator from RS Process, meets all these specific requirements for outstanding product quality," says Klaus Ertl.

The challenges

To produce valuable fish oil there needs to be minimum heat exposure on the material and the shortest treatment time of the product. The tricanter system can be tailor-made and the process is as follows.

The incoming intestines, backbones, heads or a mixture of both is minced to small particle size in a grinder. The uniform fish pulp is then fed to a loop coagulator for indirect and instantaneous heating. Usually, the heating of a fish raw material causes formation of free fatty acids (FFA) due to enzyme activity, especially in the 25 to 50 °C temperature range. In the loop coagulator, this temperature zone is passed instantaneously when the cold raw material is mixed with recycled hot material at a rate which gives a mixing temperature above the coagulation range for the proteins.

As the proteins are coagulated this prevents burning on the heat surfaces in the loop coagulator. The loop coagulator system reduces heat exposure to a minimum with the logical consequence that the oil remains nearly unaffected by heat impact. The heated raw material then flows into a buffer tank to guarantee a constant feed into the tricanter in which the hot, raw material is split into the three phases: fish oil, stick water and solids in one single step.

Liquid-liquid

Flottweg's variable impeller allows very accurate adjustment of the tricanter according to the infeed composition and therefore guarantees a perfect liquid-liquid separation without using a big separator. Contact of oil with solids and stick water, one of the main impacts on content of oil, is thus reduced to a minimum. This means the exceptionally short treatment period in the FLOTTWEG TRICANTER® contributes significantly to high, fish-oil quality.

Also, due to the special geometry of the bowl and scroll of the tricanter, as well as the completely separate discharge of the two liquids, recontamination of oil and stick water is made impossible. This results in the lowest oil content in the stick water -- the oil is already separated with a very low amount of impurities and water. There is a small polisher for further treatment of the oil, consequently reducing investment costs for this small unit. The final product, (oil with free fatty acid (FFA) contents as low as 0.1 - 0.2 %) generates extremely high sales value. One of the key-words in this field is Omega 3 fatty acid, mainly used for pharmaceutical purposes. Not only that, but the other product of the process is that further treatment of the by-products means one can also produce high-grade fishmeal. *(See WF March 2004).