When a plant-based milk feels rich, the aroma reaching the nose may matter alongside the liquid touching the tongue. In a 2024 study, adding milky-creamy flavorings to pea-protein drinks increased ratings of fattiness, thickness, and the coating sensation left in the mouth after swallowing.
However, adding flavoring did not clearly change performance in distinguishing between fat contents. The study examined feeling richer and identifying which drink contained more fat as separate questions.
Varying fat content and aroma separately
The researchers wanted to determine whether aroma changes fat-related mouthfeel in plant-based drinks, and how those changes relate to the liquid’s physical properties. They focused on whether aroma–mouthfeel relationships studied in dairy products also apply to plant-based ingredients that can have green notes, bitterness, and astringency.
The model drinks were water-based, containing a combined 3% of two pea protein isolates and 0%, 1.5%, or 3.5% rapeseed oil. At each fat level, the researchers prepared an unflavored version, a version with flavoring A, and one with flavoring B. Both were milky-creamy flavorings, but A leaned toward fatty and creamy notes, while B had coconut and fruity characteristics. Their proportions of more volatile components also differed. A was added at 0.04% and B at 0.05%.
For sensory evaluation, 30 mL samples were presented at room temperature in black cups under red lighting. Visual cues were minimized, and sample codes and tasting order were randomized. All participants were dsm-firmenich employees. Each discrimination test involved 31–36 people, while the tests describing attributes in detail involved 19–29.
Fat-content differences could be detected even with nose clips
In the first task, participants selected the sample that felt highest in fat from a set of three. Comparisons of 0% versus 1.5%, 1.5% versus 3.5%, and 0% versus 3.5% were performed with and without nose clips.
For these drinks, participants discriminated all pairs of fat levels above chance, whether or not they wore nose clips. Discrimination was also possible with flavoring A or B added, and neither flavoring nor nose clips clearly improved or impaired discrimination ability.
In other words, participants could detect differences using tastes or sensations remaining in the mouth even when aroma cues were suppressed. The authors suggest that astringency and bitterness from the plant-based ingredients may have contributed to these judgments, but the experiment did not directly isolate which sensations were used.
Flavorings increased mouthfeel ratings at the same fat content
Next, participants evaluated individual aroma, taste, and mouthfeel attributes. In the normal condition without nose clips, drinks containing flavoring A or B received higher ratings not only for milky and creamy aroma but also for fattiness, thickness as the tongue moved the liquid, and mouthcoating after swallowing.
A, in particular, tended to enhance fat-related mouthfeel more than B. Fat-containing drinks with B received higher sweetness ratings, which the authors discuss in terms of associations with fruity aroma. The character of a flavoring thus appears to influence which sensations are enhanced.
The authors also conclude that the sensory profile of the 1.5%-fat sample with A approached that of the unflavored 3.5%-fat sample. However, this comparison concerns proximity in ratings. It does not establish that the two drinks had exactly the same mouthfeel or that everyone would like them equally.
Adding flavoring did not reproduce every effect of actually adding fat. Increasing fat content also lowered ratings of astringency and green-vegetable aroma, whereas adding flavoring was not reported to produce clear changes in those attributes. In the analysis across all samples, there were also no significant differences in bitterness, cereal aroma, or cardboard aroma.
Checking whether the liquid itself became physically thicker
If flavoring changed the liquid itself, aroma alone could not explain the mouthfeel changes. The researchers therefore measured oil-droplet and particle size, viscosity, and how effectively the liquid lubricated two surfaces.
Increasing actual fat content slightly raised viscosity and reduced friction. The lubrication measure was positively associated with fattiness, thickness, and mouthcoating ratings, and negatively associated with astringency. In contrast, viscosity did not correlate significantly with the sensory ratings. At least in this low-fat model, lubrication properties offered more insight into fat perception than viscosity alone.
When samples with the same fat content were compared, adding a small amount of flavoring produced no significant differences in particle size, viscosity, or friction. Furthermore, when the three 3.5%-fat samples were evaluated with nose clips, differences in taste and mouthfeel between flavored and unflavored samples were no longer significant. Together, these findings support the explanation that aroma reaching the nose changes ratings of sensations in the mouth.
Interpreting how a creamy aroma connects sensations
The authors interpret the findings as an effect of associations between milky-creamy aroma and the mouthfeel of fatty foods. This is a cross-modal interaction, in which one sense influences another. The experiment fits that explanation, but did not measure learning from past food experience itself or processing in the brain.
The study covered two flavor formulations and pea-based model drinks, and the detailed evaluation with nose clips was limited to 3.5% fat. It also used an employee panel to rate attributes rather than studying general consumers’ preferences, satisfaction, or actual intake. Applying the findings to products requires those questions to be examined separately.
Summary
Adding milky-creamy flavorings to pea-protein drinks increased ratings of fattiness, thickness, and mouthcoating even at the same fat content. The lack of significant physical changes, together with nonsignificant taste and mouthfeel differences in the 3.5%-fat nose-clip condition, suggests that aroma may supplement fat perception.
However, neither flavoring nor nose clips clearly changed the ability to discriminate fat levels, and the lubrication properties provided by actual fat were also associated with mouthfeel. The study shows that understanding richness in plant-based drinks involves not only fat content and physical properties, but also the aromas associated with those sensations.
The research was funded by dsm-firmenich. At the time of the study, six of the seven authors were affiliated with its divisions, and sensory-evaluation participants were also company employees. The paper’s competing-interest declaration states “None.”
Reference
Vossen RM, Gelin J-L, Hettinga K, et al. Improving plant-based protein drinks: The potential of flavors for cross-modal enhancement of fat perception. LWT. 2024;213:117016. doi:10.1016/j.lwt.2024.117016
