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Less bitter, just as satiating—study on pea protein hydrolyzates delivers surprising findings

A by the Leibniz Institute for Food Systems Biology at the Technical University of Munich shows that less bitter-tasting pea protein hydrolyzates can induce just as strong satiety signals in stomach cells as their more bitter counterparts.

The findings are published in the journal Food Chemistry.

The key factor is that new bitter-tasting protein fragments are formed in the gastric juice during digestion, which stimulate the release of gastric acid and the neurotransmitter serotonin—both signals contribute significantly to the feeling of satiety in the body. The study results open up new perspectives for the development of plant-based foods that combine health, pleasant taste, and sustainability in a useful way.

Pea protein hydrolyzates are powders made from enzymatically or chemically broken down pea proteins. They consist of a mixture of small protein fragments, known as peptides, and free amino acids. They are currently gaining importance in food production because they are considered easily digestible, have a high-quality amino acid profile, and promote satiety.

"However, a major drawback is their often intense bitter taste, which many consumers dislike," explains Katrin Gradl, first author of the study and doctoral candidate at the Leibniz Institute. "Our goal was therefore to find ways to overcome this taste barrier without losing the satiating effect of the products," adds principal investigator Veronika Somoza.

The challenge

However, bitter peptides can trigger signals in the stomach that increase the feeling of satiety. Simply reducing the bitter taste of protein hydrolyzates could therefore also reduce the satiety effect.

"However, our previous studies with milk proteins had shown that such bioactive, bitter-tasting peptides do not necessarily have to be present in the starting product, but can also be formed in the gastric juice during digestion," explains co-author Phil Richter from Somoza's team.

Against this background, the research team simulated the gastric digestion of a bitter and a less bitter protein hydrolyzate using artificial gastric fluid and then analyzed the newly formed peptides.

Digestion products with a satiating effect

Using chemical and computer-assisted analysis methods as well as sensory tests, the research team identified three bitter peptides in each of the two digestion products. All six peptides stimulated the secretion of gastric acid and the release of serotonin in a human stomach cell line, regardless of the original bitterness of the product.

"It was remarkable that the peptides from the less bitter-tasting hydrolyzate stimulated serotonin release particularly strongly," reports Gradl. In addition, the researchers demonstrated that two types of bitter receptors were involved in inducing satiety signals in the cellular test system.

"Even less bitter-tasting pea protein hydrolyzates can form bioactive peptides during digestion in gastric fluid, which induce satiety signals via bitter taste receptors." However, Somoza emphasizes, "Human studies are needed to definitively assess the influence of these peptides on human eating behavior and weight control."

Nevertheless, the study already reveals molecular mechanisms that can be used to optimize the taste of protein hydrolyzates in a targeted manner—without limiting the satiating effects triggered by bitter-tasting compounds.

Plant proteins are considered an environmentally friendly alternative to animal proteins, as their production requires about five to 10 times less energy and water and around 80% less agricultural land.

Morbid obesity (adiposity) is considered a widespread disease with serious consequences such as type 2 diabetes and certain types of cancer.

A protein-rich diet can help to better control body weight as it increases satiety and thus counteracts excessive energy intake. Studies have also shown that encapsulated bitter-tasting compounds induce satiety in healthy adults by activating extra-oral bitter taste receptors.

Serotonin is one of the most important hormones that regulate food intake. More than 90% of the serotonin in our body is found in certain cells of the gastrointestinal mucosa and the nervous system.

Both the intestines and the stomach are involved in hormonal hunger and satiety regulation. Some bitter-tasting compounds can stimulate gastric acid secretion, increase serotonin release from stomach cells, delay gastric emptying, and have a satiating effect.

Interestingly, protein fragments such as bitter-tasting peptides and amino acids are also among the bitter-tasting compounds with a satiating effect.