Process water from the seafood industry is typically treated as waste, but researchers say that it contains valuable nutrients which could be used in food or aquaculture feed.
During preparation of herring, shrimps and mussels, large amounts of process water are continuously pumped out as waste by the seafood industry. The water is used when boiling shrimps or mussels, or when filleting, salting and marinating herring, for example.
However, these side stream waters contain proteins, peptides, fats and micronutrients, which could be recycled and used by the food industry, as an ingredient in feed, or for growing microalgae.
The Nordic project NoVAqua, coordinated by Professor Ingrid Undeland of the Department of Biology and Biological Engineering at Chalmers University of Technology, has now shown the potential of extracting these important nutrients from the process waters.
”It’s very important to help the industry understand that the side streams don’t need to be wasted. Instead, they should be treated as really exciting raw material,” she says.
“The backbone of our project is a circular approach. In the past, we had a more holistic view on handling of food raw materials, but today so much is lost in side streams.
“Furthermore, we are in the middle of a protein shift, and there’s a huge demand in society for alternative protein sources.”
The research project started in 2015 with the aim to recover nutrients from seafood process waters and create innovative uses for them.
A similar approach is already successfully implemented in the dairy industry, where the residual liquid from cheese making (whey) is used in sports nutrition, as well as in different food and feed products.
When the research team measured the composition of process waters, they found them to contain up to 7% protein and 2,5% fat. In process waters from shrimp, astaxanthin – a red pigment and antioxidant often used as a dietary supplement – was also present.
”Our calculations show that in a primary processing plant for herring, as much as 15% of the herring protein coming in to the industry leached out into the water and was treated as waste, thereby lost,” says Ms Undeland.
Using a two-step process, the research team managed to recover up to 98% of the protein and 99% of the omega 3-rich fats. The process resulted in a semi-solid biomass and a nutrient-rich liquid.
After dehydration, biomass from shrimp boiling water was shown to contain 66% protein and 25% fat. Two tests were made, together with the University of Gothenburg and Skretting ARC, using this new biomass as an ingredient in feed for salmon, and the results were encouraging.
The nutritious liquid was used for glazing frozen fish, thereby protecting it from going rancid. It turned out to be slightly more protective than water, which is currently used for such glazing.
The fluid was also tested as a substance for microalgae-cultivation and was shown to enhance the growth of two types of algae. The algae biomasses can subsequently be used as sources of protein or pigment.
All in all, the research project pointed out several different ways to recycle the nutrients which are currently lost in the process waters. The next step is implementation in the seafood industry.
“A major challenges is to get the industry to manage the water side streams as food, beyond the stage when they are separated from the seafood product,” says Ingrid Undeland
“Today, that is the point where the side streams start being handled as waste. This means there’s a need for new routines for cooling and hygiene.”