When the meat is eaten up, there is medicine in the bones that are left behind. Liudmila Sorokina has found out how substances in chicken residues help with both diabetes and high blood pressure.

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  Georg Mathisen

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Once the slaughterhouse filleted out the chicken meat, Sorokina takes care of the leftovers. She is a research fellow at Nofima. There, she is pursuing her doctorate on chicken processing by-products.

Cuts proteins

Or, rather, she is doing a PhD on healthy substances found in chicken by-products. In other words, what remains of the chicken after first the butcher and then the machines have helped themselves to everything that humans can eat. “What we’re going for is the protein-rich leftovers,” she says.

She uses enzymatic protein hydrolysis. Enzymes are natural substances found in all living organisms. They ensure that other substances are either assembled or split up. In this case, enzymes and water are used to split proteins.

“We mix the raw material with water and specialized enzymes. When we’re done, there are bones at the bottom. At the top there is fat. What we’re interested in is what’s floating in the middle. There, the enzymes have cut up proteins into shorter parts: peptides,” explains Liudmila Sorokina.

Blood pressure

There are several peptides found in the product after the enzymes finishes cutting up the protein. They can have completely different functions in the body. “We have removed the water and extracted a powder containing many different peptides. When we change the temperature, time or enzymes we add, we can extract completely different products from the same raw material. In my project, there have produced 60 different such hydrolysates. What we want to know is which of them have the impact we want,” she says.

The amounts are too small to extract a single peptide. Therefore, it is important to find the right group. A group of peptides enough in amount to be separated out and developed as a product, and at the same time exactly the group of peptides that works best.

“In the first project, we have developed a peptide that can regulate blood pressure. We have had a mixture of all kinds of peptides with different lengths, which we have grouped according to size,” says Sorokina.

Dietary supplement

Liudmila Sorokina and Sileshi G. Wubshet have studied how leftover chicken can help with diabetes and high blood pressure.

She has used two methods that find out how different substances are composed: chromatography and mass spectrometry.

“Then we can find out not only the health effects, but also the structure of the molecules,” says Sileshi G. Wubshet. He is a senior researcher at Nofima and has been a supervisor while Liudmila Sorokina has worked on her doctorate.

This structure of the molecules is important to know when the research is to be turned into a finished product. In this context, we are talking about a dietary supplement that can work against both high blood sugar and high blood pressure.

Artificial stomach and intestines

Liudmila Sorokina has also looked at how the peptides she discovered manage to survive the harsh conditions of the stomach and intestines of humans.

“Peptides are food. We humans are very good at turning what we eat into energy. The danger is that the peptides gets digested in the stomach and loses the important health-promoting effect. The peptides should not only survive in the stomach. They should also cross the other biological barriers and rich where they have an effect in your body,” says Sileshi G. Wubshet. “What we’ve found is that they’re stable in stomach and intestinal conditions,” says Sorokina.

For such experiments, Nofima has its own artificial gastrointestinal model. It offers the same conditions as the digestive system of a human being.

Facts about the doctoral degree

Liudmila Sorokina defends her thesis on 3 May. The title of the defence is Bioactive peptides from poultry by-product hydrolysate targeting cardiometabolic diseases: production, characterization, and bioavailability.

The public defence will take place at the University of Oslo, Kjemibygget Auditorium 2. The trial lecture starts at 10.15. Supervisors are senior researcher Sileshi Wubshet, researcher Anne Rieder, researcher Shiori Koga (all at Nofima) and professor Steven Ray Haakon Wilson (UiO).

The doctoral degree is funded by Nofima, through the internal strategic project PepTek: Peptide technology for future protein production. Other current projects are TailoTides and SusHealth.


Liudmila Sorokina et al: Multivariate correlation of infrared fingerprints and molecular weight distributions with bioactivity of poultry by-product protein hydrolysates. Journal of Functional Foods, 2022, doi: 10.1016/j.jff.2022.105170

Liudmila Sorokina et al: Low Molecular Weight Peptide Fraction from Poultry Byproduct Hydrolysate Features Dual ACE-1 and DPP4 Inhibition. ACS Food Science & Technology, 2023, doi: 10.1021/acsfoodscitech.3c00417