“Blue burgers from the sea”: Researchers unlock novel method to extract sea lettuce protein

Researchers at Chalmers University of Technology in Sweden have discovered a new way to extract protein in sea lettuce “three times more efficiently” than what existing methods allow. 

Sea lettuce (Ulva fenestrata) is a type of seaweed that can be combined with meat and other meat sources for protein. It also does not need to be watered, fertilized or sprayed with insecticides, making it a cost-effective protein solution.

“Sea lettuce holds good potential as a sustainable protein source, and several key factors support its use as a future protein ingredient. It is a high-yield crop since annual biomass productivity can surpass soybean,” João Trigo, Ph.D. in food science at Chalmers, tells Food Ingredients First.

“We have conducted these calculations with our long-term collaborator, the seaweed producer Nordic Seafarm, which is engaged in offshore cultivation of sea lettuce. The fast growth rates of sea lettuce are due to its high environmental tolerance and resistance to changing abiotic factors such as salinity, light and temperature.”

The research team notes that seaweed proteins can be tightly bound and more complex to extract than soy or pea proteins, which has prevented their full potential from being realized.

“It tastes like umami with a certain salty flavor despite not containing such high levels of salt. I would say it’s a great flavor enhancer for seafood dishes and products, but the possibilities to explore are endless. Why not protein smoothies or ‘blue burgers’ from the sea?” says Trigo.

The “untapped” potential of sea lettuce

As the global population continues to grow toward the predicted 10 billion mark by 2050, the demand for sustainable protein sources is more critical than ever.

Plant-based proteins such as soy, chickpea, fava bean and mushroom have proliferated, offering opportunities for food security and nutrition for growing populations. However, the researchers note that the vegetarian protein underwater is still “untapped.”

Under project CirkAlg, led by Chalmers University of Technology, researchers are exploring processes that can potentially create a new “blue-green” food industry in Sweden.

The extraction method is published in a proof-of-concept study in the peer-reviewed scientific journal, Food Chemistry.

“It’s fair to say there was a bit of luck involved in achieving these results, but there was also some real risk at the start with no guarantee of success. The ‘textbook knowledge’ says precipitating protein after solubilizing it with detergents is not feasible, as detergents typically shield protein charges and prevent precipitation. However, our findings defied this well-established notion,” says Trigo, referring to the “breakthrough” method that allows for a threefold increase in protein extraction efficiency.

“We discovered that, for sea lettuce, low detergent concentrations actually improved protein precipitation threefold, rather than hindering it. This was what made it possible to obtain such relatively high protein extraction efficiency.”

Cultivating sea lettuce is gentler on the planet than growing land-grown proteins, as it grows well under many different conditions, including different salinity and nitrogen levels.

Recovering “lost” nutrition

In addition to the novel method, the Chalmers team is collaborating with the University of Gothenburg in Sweden to increase the protein content in sea lettuce by cultivating it in process water from the seafood sector.

This way, the nutrients that would otherwise be wasted are injected back into the food chain.

The researchers note that cultivating sea lettuce is gentler on the planet than growing land-based proteins.“The protein content of sea lettuce is generally higher than brown seaweeds, and there is still room for improvement. So, in collaboration with Gothenburg, we have successfully improved the sea lettuce’s natural protein levels from 10-15% (dry weight) to 20-30%,” notes Trigo.

“This increase implies that, after protein extraction, we will recover a larger quantity of protein, and the resulting protein ingredient will also tend to have a higher purity. Sea lettuce can be a high source of vitamin B12, which is present in much smaller amounts in other seaweed species cultivated in Europe. We are studying this nutrient — often lacking in vegan diets — and the results are encouraging.”

Mainstreaming seaweed

Trigo believes that once production volumes of seaweed have multiplied in Europe, seaweed-based protein ingredients can play a more significant role as main ingredients in a variety of food products.

“A new seaweed protein ingredient would initially be one of several other alternative protein ingredients in protein-rich foods, bringing in unique values such as vitamin B12, unsaturated fatty acid, saltiness, umami and marine flavors.”

“About consumer perceptions, investigations done within CirkAlg have revealed that consumers have an overall positive attitude toward seaweed as a food. We think this could be further enhanced with parallel communication of the many environmental advantages linked to seaweed cultivation and seaweed as a new alternative protein source; for example, the absence of competition for arable land,” Trigo concludes.