Seafood processing water is a surprising source of nutrients

tub of herring
Public Domain Unsplash – A tub of herring

Instead of tossing it, fisheries should capture the protein and fat left in water and use it to feed humans and animals a second time around.

When fish and crustaceans are taken from the ocean for eating, they are held and/or processed in tanks filled with seawater. A one-ton batch of pickled herring requires up to 8,000 litres of water to process, and 50,000 litres is needed for either 1 ton of peeled shrimp or 3 tons of unpeeled.

Afterward, this water is treated and disposed of, often at a fairly high cost to fisheries. (One study says fisheries in India pay between US$500 and $1,500 per day.) But researchers at Chalmers University of Technology in Sweden, led by Dr. Ingrid Undeland, have found that seafood processing water could actually be a valuable resource.

The leftover water is filled with protein, omega-3 fatty acids, minerals, lipids, and antioxidants. Its composition can contain up to 7 percent protein and 2.5 percent fat. Dr. Undeland told Seafood Source that, when herring is processed, up to 15 percent of its protein leaches into the water. There's no reason why this source of nutrients couldn't be used to feed humans and animals a second time around. Her team set out to extract the nutrients and experiment with various uses.

"Using a two-step process, the research team managed to recover up to 98 percent of the protein and 99 percent 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 percent protein and 25 percent fat."

These byproducts have been used in several ways. The biomass was fed to salmon, which are carnivores and typically eat a diet of ground-up fish and other sea animals when farmed. The nutrient-rich liquid was used to 'glaze' frozen fish, which helps to preserve this. Usually this is done with water, but this liquid was found to be even better at extending the product's lifespan. Finally, the liquid was used to grow two types of algae (another great sustainable source of protein) and did "enhance" its production.

Seafood Source reported,

"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."

The Novaqua project, as it's called, takes inspiration in part from the dairy industry, which created uses for whey, the liquid left over after cheese-making, where previously there were none. Now we have shelves full of whey-based protein powders and dietary supplements. Seafood processing water could be thought of in a similar way.

This research comes at a time when demand for protein is higher than ever. Food Tank cites a study that found "overall meat consumption increased by almost 60 percent between 1990 and 2009," and that demand is only going to grow. Meanwhile, the environmental impact of meat production is becoming more serious, using and contaminating enormous quantities of water, driving greenhouse gas emissions, and incubating diseases. The oceans, too, are being overfished and many species are struggling to recover.

That the world needs more sustainable sources of protein is undeniable, and seafood processing water can be a part of that solution.

Seafood processing water is a surprising source of nutrients
Instead of tossing it, fisheries should capture the protein and fat left in water and use it to feed humans and animals a second time around.

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