Several million tonnes of fish are processed annually by the European fishing industry. The processing of this material produces a significant amount of filleting and gutting residues. These residues, often called as side-streams, may constitute up to 70% of the overall fish biomass. A considerable part of these side-streams is used for low-value animal feed, and a significant portion is treated as processing waste. There are valuable products that could be generated from side-streams. Converting them into value-added products has recently gained considerable attention.
Fish head, skin, viscera and bones are rich in nutrients and bioactive substances such as proteins and polyunsaturated fatty acids.
High-value products from side streams
Fish processing generates side-streams composed of heads, skins, fins, trimmings, frames, internal organs, and guts. This material has traditionally been utilized as animal feeds, fertilizers, and biofuels. With the new biotechnological applications there is substantial potential for processing higher value products from these side-streams while at the same improving environmental performance. Side-streams contain valuable bioactive ingredients and fractions, such as fish oils, collagen, gelatin, proteins and peptides, and enzymes. These compounds provide opportunities to develop new applications for instance in nutraceuticals, pharmaceuticals, health promoting foods, and cosmetic products.
In addition, the fishing industry produces also large quantities of low-value fish species, often caught as bycatch, which are under-utilized in economic terms. This resource comprises another source of potential high-value products.
Every component of fish can be utilized
Bones and scales make up 14–20% of the fish’s weight. About 60–70 percent of the bones are inorganic compounds such as calcium, phosphorus and other minerals. These are used in various supplements for humans and animals. Calcium and phosphorus can also be utilized in chemical industries. Components extracted from fish bones can be used in medical applications to replace synthetic materials. Scales are used as the raw material of biodegradable films.
Collagen is obtained from fish skin, scales and bones, and can be refined into gelatin and bioactive peptides. Collagen is used, for example, in various cosmetic products. Gelatin can be used to make water-soluble gels and films for example for products that require encapsulation in the pharmaceutical industry. In the near future, bioactive peptides may be used in the treatment of various diseases.
Fish’s internal organs make up about a fifth of the fish’s weight. Internal organs are a significant source of digestive enzymes. There are various applications for such enzymes especially in the food and detergent industry. Fish enzymes are particularly good because they react at low temperatures. For this reason, they are used for example in the dairy industry. Low-value fish roes have also proven to be good raw materials. They can contain plenty of vitamin D and good quality fatty acids.
Challenges and innovation actions
Collecting, storing and refining side-streams into a usable form cost-effectively is a challenging task and often require large investments and high skills. Furthermore, sources of filleting and gutting residues as well as low-value bycatches are often scattered in different places. Clearly, logistical, infrastructural and technological challenges to efficiently deliver side-streams from various sources to biorefining operations needs to be resolved before any further actions are taken. To obtain sufficient compounds towards the value-added applications, the initial stages of the valorisation processes must also identify and specify the potential of the different types of side-streams.
It is noteworthy that the recent developments in biotechnology with higher market prices makes it possible to generate added value from smaller and more scattered side streams than previously. There are new technological solutions available to boost the exploitation of side-streams. The ultimate objective is to ensure the valorisation of side-streams into marketable products and a source of income.
Conditions are favourable
In conclusion, the current exploitation of the aquatic resources is hampered by inefficiency as up to 70 % of residues ends up as low-value products or waste. Increasing the degree of processing of side-streams would improve the industry’s overall profitability and sustainability. In order to utilize these side-streams for higher value purposes, provision of proper logistics and infrastructure to ensure high quality of side-streams is essential. Promising technologies and approaches are available.
Conditions are favourable for the environmentally sustainable production of various high-value products using side streams. This requires a purposeful operational policy and wide-ranging cooperation between sectors. New innovations, technologies and value chains will continue to be key in solving the logistical challenges. The International Seafood Consulting Group (ISCG) is ready and able to act as a coordinator in this transition.
