HMN 2025: How Pea protein hydrolysates affect satiety differently based on bitterness and breakdown

Protein hydrolysates are produced by breaking down proteins into short protein fragments (peptides) and amino acids. They are playing an increasingly important role in the production of plant-based foods.

In a new human study, researchers from the Leibniz Institute for Food Systems Biology at the Technical University of Munich and ZIEL—Institute for Food & Health of the Technical University of Munich have shown that different hydrolysates from pea protein influence satiety in different ways. The study, published in Molecular Nutrition & Food Research, provides a scientific basis for the development of new foods that support nutritional strategies for weight regulation.

The demand for plant-based protein sources is growing because their production requires significantly less energy, water, and land than animal products. Protein hydrolysates are becoming particularly important in food production because they are versatile and easy to process technologically. However, one disadvantage of such hydrolysates is their often bitter taste, which many consumers find unpleasant. “This is due to certain peptides and free amino acids,” says Katrin Gradl, first author of the study.

However, recent studies suggest that these bitter compounds may influence satiety, for example, by slowing gastric emptying or promoting the release of satiety hormones. Similarly, research indicates that less extensively hydrolyzed proteins primarily delay gastric emptying. More extensively broken-up proteins pass through the stomach more quickly and are thus more likely to trigger a hormonal satiety response in the intestine.

Pilot study with two different pea protein hydrolysates

To test these hypotheses, the research team led by Veronika Somoza, research group leader at the Leibniz Institute, conducted a pilot study with 19 overweight men (body mass index 25–30 kg/m²). The focus was on how the degree of hydrolysis and the degree of bitterness of two different pea protein hydrolysates affect satiety regulation.

In the current pilot study, the subjects received 15 grams of one of the two pea protein hydrolysates two hours before a test breakfast on different study days. The protein hydrolysate H1 was less bitter and more hydrolyzed (degree of hydrolysis 35%). The other hydrolysate, H2, tasted more bitter, was less hydrolyzed (degree of hydrolysis 23%) and therefore more difficult to digest.

The researchers then recorded how much energy the participants consumed at breakfast. They were allowed to eat as much as they wanted. The researchers also examined how quickly the participants’ stomachs emptied and their hormone levels in the blood.

What the study shows

Participants who received the more bitter, less broken-up hydrolysate H2 showed delayed gastric emptying and consumed an average of around 126 kilocalories less at breakfast. The less bitter-tasting and more highly hydrolyzed product H1, on the other hand, significantly reduced ghrelin and DPP4 concentrations in the blood without affecting short-term energy intake. A low ghrelin level signals less hunger to the body. A lower DPP-4 concentration causes satiety hormones to remain active longer, thereby promoting satiety.

“Our results show that both hydrolysates influence the feeling of satiety in different ways. Hydrolysate H2 quickly made the subjects feel full, so they ate less. Hydrolysate H1, on the other hand, had a delayed effect and presumably promotes a longer-lasting feeling of satiety between meals,” explains principal investigator Somoza.

“Both bitterness and degree of hydrolysis played a decisive role in this. The study thus provides valuable insights for the development of functional foods that can contribute to reducing energy intake in a natural way.”

The body mass index (BMI) is a measure used by researchers to estimate a person’s body weight and classify them as underweight, normal weight, or overweight. It is calculated by dividing body weight in kilograms by height in meters squared.

The limits for BMI are as follows: a BMI below 18.5 means underweight, a BMI between 18.5 and 24.9 is considered normal weight. A BMI of 25.0 to 29.9 is considered overweight, and a BMI of 30.0 or above is considered obese. It should be noted that these values apply to adults and may vary depending on age, gender, and muscle mass.

Pea protein hydrolysates and degree of hydrolysis

The pea protein hydrolysates currently available on the market are partial hydrolysates, which are obtained through chemical or enzymatic cleavage processes. In partial hydrolysates, the cleavage process is not completely finished, so that larger protein residues remain in addition to free amino acids and short peptide chains.

The degree of hydrolysis indicates how many peptide bonds in a protein hydrolysate have been cleaved in relation to all peptide bonds in the original protein. It therefore indicates the extent to which the long protein chains have already been broken down into shorter peptides and amino acids.

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