The new review, published in Trends in Food Science & Technology, examined the potential challenges and realistic opportunities for the use of processing by-products in the food production and feed sectors – finding thatmost realistic uses of by-products from processing of fish are as food or indirectly as food by producing feed ingredients rather than as sources for high-value novel ingredients.
Led by Ragnar Olsen from the Food and Agriculture Organization (FAO) of the United Nations, the review team noted that the industrial processing of fish and shellfish may result in as much 70% of by-products – much of which has traditionally been considered to be of low value and have been used as feed for farmed animals, as fertilizers or simply discarded.
However, the team noted that improving the use of such waste products has been a core focus of many within the industry for several years due to the potential environmental benefits in addition to increased economic possibilities and the potential to produce more food from limited resources.
“As in all kinds of production, transformation of by-products into commercial products must be market-driven or create a product that has a realistic possibility of being sold with an economic margin within a reasonable time period,” wrote the reviewers.
According to the FAO team, however, there are many distinct challenges with increasing the utilisation of waste products – including the fact that much of the processing of fish and shellfish is often carried out at sea.
“Modern industrial processing is usually carried out in a stepwise manner, creating separate streams of by-products that can be taken care of and diversified into different end products,” wrote Olsen and his team. “This may be carried out in land-based processing facilities, but is more of a challenge if the fish are processed at sea, mainly due to lack of space and not enough manpower on-board most fishing vessels.”
“When fish are gutted at sea, the viscera are often discarded since available ice, refrigeration or freezing facilities are used for the most valuable product; the gutted fish. The same is often the case with heads and frames if the fish is further processed to fillets on-board. Higher yearly quotas or more fishing days to fishing vessels which do not discard by-products at sea might be one way to encourage landings of by-products.”
Food-grade by-products?
The FAO team noted that if treated correctly, the remains of the fish - commonly called by-products – are generally classified as category 3 by-products according to EU regulation, meaning parts of animals that are fit for, but not intended for human consumption.
However, they conceded that the ‘up-grading’ of by-products to so-called co-products intended for human consumption requires that quality assurance systems such as Good Manufacturing Practice (GMP) and the Hazard Analysis and Critical Control Point (HACCP) used in food production are applied.
“This is currently not always possible due to unsuitable processing facilities, lack of relevant equipment or labour costs,” said the team.
Bioactive potential?
Olsen and his colleagues added that in addition to the use of by-products directly as human food or for producing preserved feed ingredients like fishmeal, fish protein concentrates and fish oil, much focus has been to transform this biomass into functional or bioactive ingredients and value-added products that could – for example – be used in dietary supplements and nutraceuticals.
“The rising prices of fishmeal and fish oil due to the demands of the expanding aquaculture industry suggest that these products probably should not be regarded as low-value products anymore,” said the team.
However they added that the isolation of high-value bioactive compounds from by-products is - with the exception long-chain omega-3 fatty acids from certain materials – “not very realistic in most cases.”
“Important reasons for this are lack of existing markets, too small amounts of high quality by-products available on a regular basis, high costs of isolating specific components often present in small amounts and the challenges connected with providing the documentation required for a potential nutraceutical product,” wrote Olsen and his team.
In addition, they noted when molecules with commercially interesting properties are identified in a by-product it is generally cheaper and more stable to then use chemical synthesis or genetically modified microorganisms for production of the molecule.
“Although sometimes suggested, it is unlikely that by-products can be used to any large extent to produce high-priced products,” they concluded. “The most realistic uses of by-products from processing of fish are as food or indirectly as food by producing feed ingredients.”
Source: Trends in Food Science & Technology
Volume 36, Issue 2, Pages 144–151, doi: 10.1016/j.tifs.2014.01.007
“Challenges and realistic opportunities in the use of by-products from processing of fish and shellfish”
Authors: Ragnar L. Olsen, Jogeir Toppe, Iddya Karunasagar