Does Seeing Strawberries Make an Odorized Drink Taste Sweeter?

Can added odors and pictures of food change sweetness ratings even when the sugar concentration stays the same? In a 2011 study, a group shown recognizable pictures of strawberries and caramel rated odorized sugar solutions sweeter overall than a group shown abstract images retaining the colors and patterns of the originals.

The study focused not just on color but on recognizing what food an image depicts. It examined how image meaning and picture–odor combinations work when taste, smell, and vision come together.

Keeping sugar concentration constant while changing image recognizability

The participants were 48 healthy adults randomly assigned to two groups of 24. One group saw concrete pictures of strawberries and caramel. The other saw images that retained the originals’ colors and fine textures but scrambled the shapes of the objects. The study did not have participants view both types, to avoid concrete pictures revealing what the abstract images depicted.

All liquids in the main test were 6% sucrose solutions. They contained either a strawberry odor mixture, furaneol with a caramel-like odor, or abhexon with a bouillon-like odor. A trained panel had matched the intensity of the three odors beforehand.

A device delivered 1 mL of liquid at a time to the tip of the tongue, and images appeared for 4 seconds on trials with an image. Participants rated sweetness from 0 to 100 immediately after swallowing and rinsed with water between samples. At the beginning, they also rated unflavored 4%, 6%, and 8% sugar solutions to experience the sweetness range.

Higher ratings for strawberry odor and the concrete-image group

For the initial unflavored sugar solutions, greater sugar concentration produced higher sweetness ratings, with no significant difference between the groups. For the subsequent odorized samples, analyses adjusting for participants’ scale use and their ratings of 6% sugar solution found higher sweetness ratings overall in the concrete-image group.

There were also differences between odors. Across all conditions, strawberry odor was rated sweeter than caramel-like odor. Its difference from bouillon-like odor did not reach significance in this comparison. Considering only trials without an image, strawberry odor received higher sweetness ratings than either of the other two odors.

The prediction that caramel-like odor would enhance sweetness more than bouillon-like odor was not supported. The authors suggested that using single compounds for caramel and bouillon may have mattered, because these differ from the complex food odors people ordinarily experience. The specific odors selected can therefore influence the results.

Ratings rose on trials displaying abstract images

Comparing trials with and without images, the abstract-image group showed a pattern of higher sweetness ratings when an image was present. In the concrete-image group, by contrast, ratings were already high on no-image trials, with no clear additional increase from displaying an image.

The authors explained this combination in terms of two processes: concrete images having a lasting effect mediated by memory, and abstract images having a temporary, immediate effect. However, the paper contains a reporting problem relevant to this persistence interpretation. Its procedure section describes six no-image trials first, followed after a break by 12 trials with images. The results and figure description, in contrast, say that no-image trials were interspersed among image trials.

This discrepancy in trial order matters when deciding whether an image’s effect persisted afterward. The group rating patterns are reported, but they alone cannot establish that the sweetness effect of a photograph lasts.

Picture–odor matching worked differently for strawberry

The researchers also compared matching combinations, such as a strawberry picture with strawberry odor; combinations of different sweet foods, such as a strawberry picture with caramel odor; and combinations with bouillon-like odor.

The overall effect of congruency was not significant, but the results differed by picture type. With strawberry pictures, strawberry odor produced higher sweetness ratings than caramel-like odor. Caramel pictures did not show a comparable benefit from matching.

Thus, neither a blanket claim that matching pictures and odors always increases sweetness nor one that matching is irrelevant captures the results. The specific combination, including which food it evokes, matters.

Image meaning offers a clue; the memory mechanism remains a hypothesis

This study did not directly measure brain activity or memory. Some participants recognized the foods in the abstract images, and half reportedly recognized them partially. Moreover, because the task asked only about sweetness, differences in other impressions, including odor, may have entered the sweetness scores.

The images were selected because they had tended to increase sweetness in a preliminary test with different participants. Further comparisons would be needed to predict the effects of all kinds of packaging or food photography from these two image types.

Summary

Odorized sugar solutions received higher sweetness ratings overall in the group viewing recognizable strawberry and caramel pictures than in the abstract-image group. Strawberry odor was rated sweeter than caramel-like odor, and strawberry pictures also showed a benefit from matching the odor.

Alongside color and pattern, the meaning of an image, including what food it depicts, offers an important clue to how odor and taste combine. Because the paper gives conflicting accounts of presentation order, the distinction between temporary and lasting effects should be treated as an interpretation requiring further verification.

In its funding and competing-interest disclosures, the paper states that some authors were employed at the time by Top Institute Food and Nutrition, Profactor GmbH, and the Center for Innovative Consumer Studies. They declared no related patents or products in development or on the market.

Reference

van Beilen M, et al. (2011). Effects of Visual Priming on Taste-Odor Interaction. PLOS ONE, 6(9), e23857. Original research article and open full text