A great deal of protein-rich fish trimmings is either discarded or used as animal feed. The world needs more high quality protein, and there is money to be made for the industry if these trimmings can be sold as food for human consumption. Protein powder is versatile and can be used, for example, as a dietary supplement, in soups and baby food.
"There is nothing new in making protein powder from fish trimmings. But the aim of my Ph.D. project was to gain a deeper understanding of how a so-called hydrolysis process affects the degradation of fish proteins and how it affects the taste formed in the end product," explains Aspevik, a research fellow with Nofima, the Norwegian food research institute, and the University of Bergen.
Aspevik has therefore carried out a systematic study with a view to finding out which enzymes and process conditions produce a good taste at the lowest possible cost. The knowledge gleaned from this work is freely available for the industry to exploit.
This is new, and makes it possible to exploit fish trimmings in food for human consumption.
Cutting up proteins
One of the main challenges presented by the hydrolysis process is that the end product has a bitter taste. This is due to the size and composition of the peptides.
"By using enzymes, which are small biological scissors, one can chop up the proteins found in the trimmings into smaller peptides," explains Aspevik. These peptides dissolve easily in water and can be utilised easier in a variety of products than is the case with the intact protein.
Enzymes are expensive, and to create a product which is commercially feasible one criterion was to test enzymes that are already on the market at a satisfactory price. Another criterion was that the hydrolysis should run with a natural pH without the addition of acids or bases, in order to achieve the purest protein.
The starting point was fresh salmon heads and salmon backbones.
Together with colleagues at Nofima’s feed technology centre in Bergen, Norway, Aspevik tested and compared several enzymes based on cost and the enzymes’ ability to chop up salmon proteins. Nutritional and chemical properties of the final products have been tested in BioLab’s laboratory in Bergen and by the Department of Chemistry at the University of Bergen, and taste has been evaluated by Nofima’s sensory panel of judges. In addition, techniques to reduce bitterness have been tested in the production of protein powder with a low bitter taste.
Result: Powder and know-how
With the criteria that Aspevik had assumed, she managed to produce high quality protein powder with a significantly lower bitter taste. The product still has a characteristic fish taste. Protein powder is nutritious and contains all essential amino acids.
"There is therefore a great potential for increased exploitation of trimmings in the production of fish protein powder as food for human consumption," Aspevik believes.
Meanwhile, the study has shown that the enzyme selected and how long the process takes are important for the formation of a bitter taste. A more bitter taste is associated with high yield of dissolved protein and small peptides.
