Does Vanilla Aroma Make Milk Taste Sweeter?

Can adding vanilla aroma make milk taste sweeter without adding more sugar? In 2018, Gloria Wang and colleagues asked 108 people to taste 18 types of skim milk to investigate how vanilla and sugar change each other’s perception.

The study was not simply asking whether milk containing vanilla would be rated sweeter. Would the effect remain even when separate response scales were available for “sweet aroma” and “sweetness tasted on the tongue”? And would the combined effect exceed the sum of the effects of the two ingredients separately?

Are people simply reporting aroma impressions on the sweetness scale?

Aromas associated with sweet foods, such as vanilla, have been reported to enhance perceived sweetness. But if an experiment asks only “How sweet is it?”, participants may include their impression of the aroma in their sweetness score. Researchers view this as a problem of assigning a sensation to another response category because an appropriate category is unavailable.

In everyday eating, however, people do not necessarily separate aroma, taste and mouthfeel in detail. Asking them to evaluate each separately in an experiment may itself change how they perceive flavor. With this issue in mind, the study used a real food, milk, and a wide range of formulations including concentrations used in products.

108 people evaluated 18 milks over three days

The participants were 108 people aged 19–71 who drank skim or low-fat milk at least once a week and were interested in tasting vanilla-flavored milk. They evaluated six samples per day, completing all 18 over three days.

Added sugar ranged from 0% to 5% by weight, and two-fold vanilla extract from 0% to 0.75%. Rather than samples containing only isolated aroma compounds, the researchers used a product made by extracting vanilla beans in water and ethanol. Formulations containing sugar alone, vanilla alone or both were tested alongside plain skim milk.

Samples were served at 5°C with three-digit codes that did not identify their contents. Presentation order was balanced across participants. Participants first rated liking on a nine-point scale, then rated the intensities of “sweetness,” “vanilla flavor,” “milk flavor” and “thickness (the sensation of viscosity)” separately on 0–100 scales. Providing a separate response scale for the aroma impression was a key feature of the experiment.

Vanilla slightly increased sweetness, while sugar strengthened vanilla flavor

Modeling the overall relationship between concentrations and ratings showed a small but statistically significant increase in sweetness as vanilla increased. Separating the aroma and sweetness rating scales did not entirely eliminate the effect on sweetness.

Nevertheless, sugar concentration remained the main influence on sweetness. In the model, increasing vanilla extract by 0.1 percentage points increased sweetness by about 0.5 points on the 100-point scale. This is an estimate calculated from the relationship between concentration and average ratings, not proof that every person could clearly distinguish the difference.

There was also an effect in the opposite direction: increasing sugar substantially increased ratings of vanilla flavor. The authors reported that sugar’s enhancement of vanilla flavor was more pronounced than vanilla’s enhancement of sweetness. The study suggests that reducing sugar in a vanilla-flavored food may change not only sweetness but also its vanilla character.

The authors discussed this interaction in terms of the integration of taste and aroma in perception. However, the experiment did not measure brain activity, nor did it directly measure volatiles released from the extract to establish the mechanism.

A combination that exceeds simple addition is not necessarily better at higher concentrations

“Adding vanilla increases sweetness” is not the same as “combining the two produces more than the sum of their separate effects.” The researchers used the concentration–sweetness relationships for sugar-only and vanilla-only milks to establish a no-interaction reference. They then examined how far the sweetness of milks containing both ingredients departed from it.

In this analysis, four of the nine mixed formulations showed evidence of synergy beyond the authors’ chosen criterion. These combined 1.31% or 2.24% sugar with 0.30% or 0.435% vanilla extract. Synergy was most apparent at low to medium concentrations, and the mixtures with the most vanilla did not meet the same criterion.

Synergy here is a mathematical classification based on concentrations and ratings. The authors noted that further work is needed to establish how meaningful differences in this index are to consumers and whether the same criterion applies to other foods. The proportion of formulations showing synergy cannot be reinterpreted as a percentage reduction in sugar.

“Sweet” and “liked” follow different curves

Liking did not keep rising as vanilla and sugar increased. In the model relating concentrations to liking, the most preferred point was around 3.79% sugar and 0.53% vanilla extract. These are model values fitted to the data for this skim milk, extract and participant group, not a universally optimal formulation for vanilla milk.

Given the small aroma-induced enhancement of sweetness, the authors suggested that using it for sugar reduction would probably require combining it with other approaches. They also proposed checking the interaction with methods that compare foods as integrated wholes, rather than only rating individual flavor attributes as in this study.

Summary

In this skim-milk experiment, vanilla aroma slightly increased sweetness. The effect remained even with separate response scales for sweetness and aroma, and some formulations showed an interaction beyond simple addition. However, the effect was small, and more vanilla did not necessarily increase either synergy or liking.

Equally important, sugar changed how vanilla was perceived. Vanilla and sugar do not divide neatly into aroma and sweetness roles; together they create the flavor experienced while drinking. The study indicates that developing enjoyable reduced-sugar foods requires adjusting the formulation with aroma impressions in mind, rather than restoring sweetness alone.

References

Wang, G., Hayes, J. E., Ziegler, G. R., Roberts, R. F., & Hopfer, H. (2018). Dose-Response Relationships for Vanilla Flavor and Sucrose in Skim Milk: Evidence of Synergy. Beverages, 4(4), 73. DOI: 10.3390/beverages4040073 / Full original article.

Original article: © 2018 by the authors. Licensee MDPI, Basel, Switzerland. CC BY 4.0.