How is Fish Protein Powder made?

The manufacture of types A and B is described here, since type C is simply hygienically prepared fish meal.

Water and fat together constitute about 80 per cent of the whole fish, with the fat itself in some species accounting for up to about 20 per cent at times. The manufacture of FPC involves removal of most of the water and some or all of the fat. Methods developed so far are based mainly on the use of chemical solvents to remove the water, fat and fishy-tasting components, either from raw fish or from fish meal. The solvents most successfully used to make FPC type A are the alcohols, for example ethanol or propanol; ethylene dichloride is also used. The choice between ethanol and propanol is based on cost, but since propanol is usually free of excise tax it has tended to replace ethanol. Normally the solvent is recovered and used again and again.

The manufacturing process is quite complicated, but an outline of a typical process is shown in the figure. The sequence of operations is:

1. Fresh whole fish are rinsed with fresh water soon after landing, weighed and fed to a mincer by conveyor.

2. First extraction: the minced fish are fed to extractor 1 which dehydrates the fish; it is an unheated vessel in which the mince is agitated for about 50 minutes together with the liquid recovered from extractor 2, which contains some isopropanol.

3. Centrifuging: the contents of extractor 1 are fed to a continuous centrifuge, where the slurry separates into a solid known as wet cake, and a liquid. The wet cake is conveyed to extractor 2, and the liquid to a still for recovery of solvent and fat.

4. Second extraction: extractor 2 is jacketed, and the temperature is about 75°C. Here the liquid recovered from extractor 3 is added to the wet cake from extractor 1 and the mixture is agitated for 90 minutes. At the beginning of this stage the cake is almost completely dehydrated, but has a fat content of about 5 per cent, which is reduced to about 1 per cent during the extraction.

5. Centrifuging: the contents of extractor 2 are centrifuged, the wet cake is conveyed to extractor 3, and the liquid is returned to extractor 1 for the next batch of raw material.

6. Third extraction: extractor 3 is jacketed, and the temperature is again about 75°C. Fresh isopropanol is added to the wet cake and agitated for about 70 minutes. During this stage the fat content is reduced to about 0·3 per cent.

7. Centrifuging: the contents of extractor 3 are centrifuged and the wet cake is washed with pure isopropanol for about 50 minutes. The liquid is returned to extractor 2 for the next batch.

8. Solvent removal: the wet cake is heated in a rotating vacuum dryer to evaporate the solvent; the vapours are drawn off, condensed and used again.

9. Grinding and packing: the dried material is conveyed to a hammer mill, where it is ground to a fine powder and sieved. The FPC is typically packed in 50-lb fibreboard containers and sent to store ready for shipment.