Researchers at the Norwegian Research Centre (NORCE) hope to provide seafood producers the opportunity to better exploit their by-products by processing them into fish-based protein powders for use as supplements for athletes and meal replacement for the elderly.
In a press release from NORCE, Rasmus Ree - a researcher at the facility - explains this process.
Ree explains “The way these byproducts are handled now is that they are ground and treated with a special type of enzyme, called a protease. A protease cuts the fish proteins into smaller pieces. This process is called enzymatic hydrolysis, and what we are left with is a hydrolysate. After the hydrolysis is complete, the proteins are dried and you are left with a protein powder," the NORCE researcher explains.
However, the resultant protein powder retains a strong smell and taste of fish, making it virtually unusable as a protein supplement for humans.
Ree comments “We know that a compound called trimethylamine (TMA) causes a large part of the fish smell. So the strategy we have chosen is to use an enzyme which converts TMA into trimethylamine-N-oxide (TMAO), as TMAO is smell-free. TMAO exists in fish naturally anyway. In fact, the TMA gets into the hydrolysate because after the fish is butchered, bacteria convert the naturally occurring TMAO into TMA”.
In a previous study, researchers at NORCE isolated an enzyme that can catalyse this reaction. However, the enzyme - flavin-containing monooxygenase (mFMO) - is unable to withstand the high temperature conditions required during processing and so, in this new research, the researchers tailored the structure of the enzyme to increase its heat tolerance.
“The hydrolysis process happens at a quite high temperature, 50-60 degrees, for hygiene reasons. mFMO is not stable at that high a temperature. We made some changes in the mFMO enzyme, using an advanced algorithm which takes the shape and properties of the enzyme into account and suggests modifications we can do to make it more heat resistant,” Ree says.
“When we increased the heat up to the process temperature, only the new enzyme variant could perform. Not only that, but it worked better at a higher temperature than at a lower one! This told us that the new enzyme variant can handle industrial process conditions. Now we want to test it on other raw materials, such as cod and pelagic fish, while we continue optimizing the enzyme,” Ree added.