Mint’s cooling sensation, sweetness, and sourness do not seem simply to add together independently. In a 2008 study, sweetness ratings changed with the combination of mint flavoring and a cooling agent, even though the sugar formulation stayed the same. Adding more mint increased sweetness in the condition containing more cooling agent.
The researchers also compared peach flavoring and included a nose-clip condition to suppress smell. They found different changes not only in sweetness but also in sourness, bitterness, and cooling.
Studying aroma, taste, cooling, and thickness together
The aim was to investigate how the type and concentration of an aroma affect taste, cooling, mouthfeel, and the interactions among them. Cooling can arise from chemical stimulation involving the trigeminal system, distinct from the olfactory system that detects aromas.
The researchers added peach or mint flavoring, the cooling agent WS-3, and citric acid to viscous model samples containing sugars and xanthan gum. Combining low and high levels of flavoring, cooling agent, and acid produced eight peach formulations and eight mint formulations, for 16 samples in total. Physical measurements showed similar viscosities across the samples.
The participants were 10 women with sensory-evaluation experience, with a mean age of 40. They evaluated samples at a room temperature of 22°C with and without nose clips. They rated cooling, sourness, sweetness, bitterness, and thickness; without nose clips, they also rated the odor smelled from the cup and the aroma reaching the nose from the mouth. Samples were numbered, and presentation order was arranged within each condition. However, the nose-clip condition always came first, and the order of flavoring types was not fully balanced.
Removing the nose clip had different effects for peach and mint
Peach samples were rated sweeter and less bitter without a nose clip than with one. Mint samples received higher ratings without a nose clip for cooling as well as sweetness, sourness, and bitterness. The direction of the changes when smell was available differed with the flavoring type.
When the two flavorings were compared without nose clips, peach had a stronger odor and aroma, but mint scored higher for cooling, sweetness, sourness, and bitterness. The authors suggest that effects on other sensations depend not only on how strong an aroma is, but also on what kind of aroma it is.
More mint increased sweetness when the cooling-agent level was high
A particularly important finding was the change in sweetness associated with the amounts of mint flavoring and cooling agent. Without nose clips, increasing mint flavoring raised sweetness in samples with a high cooling-agent level. In samples with a low cooling-agent level, the change in sweetness from adding more mint was not significant. The interaction between the two ingredients was also significant. Adding more peach flavoring increased odor intensity, but produced no clear changes in the other sensations.
The direction of the sweetness change when the cooling-agent level increased also differed by flavoring: sweetness decreased in peach samples and increased in mint samples. Without nose clips, adding more cooling agent also increased sourness for both peach and mint. Cooling itself increased in peach samples regardless of whether a nose clip was worn, whereas in mint samples the increase was significant only with nose clips.
Increasing the acid itself mainly increased sourness and reduced sweetness in peach samples. However, for mint evaluated without nose clips, the increase in sourness with additional citric acid was not significant. The cooling agent also reduced aroma intensity in peach samples, showing that the effects did not run only in one direction from aroma to taste.
The mint flavoring also retained a direct cooling effect
The mint flavoring had been selected in preliminary testing as one unlikely to produce cooling. In the main experiment, however, adding more mint flavoring increased cooling even with nose clips. Cooling was stronger still without nose clips, suggesting that the flavoring’s own cooling action contributed alongside the influence of smell.
For that reason, not all the changes can be attributed to the effect of mint aroma alone. The authors suggest that experiencing aroma, sweetness, and cooling together in products such as chewing gum and mint confectionery may build associations among these sensations. This study did not directly investigate that learning process or receptor activity.
The thickness results were harder to interpret
Without nose clips, samples containing more mint flavoring felt thicker. At the same time, removing nose clips lowered thickness ratings overall, for both peach and mint.
The authors note that nose clips might change mouth movements, swallowing, and mixing with saliva, and therefore withhold a firm conclusion about aroma–texture interactions. These findings came from model samples evaluated by 10 women, not from a test of liking or of how much real confectionery people ate.
Summary
When peach aroma was available, sweetness increased and bitterness decreased; with mint, ratings of cooling and several tastes rose. Furthermore, sweetness enhancement from increasing mint appeared in the high-cooling-agent condition, showing the importance of the combination of aroma, taste, and cooling.
The mint flavoring’s direct cooling effect and possible effects of nose clips on mouth movements mean that no single mechanism can explain everything. Nevertheless, the study shows that a food’s sweetness and cooling sensation depend not only on the amounts of separate ingredients but also on the aroma experienced alongside them.
At the time of the research, the authors were affiliated with the Nestlé Research Center. Givaudan supplied the flavorings and cooling agent. No separate funding section or conflict-of-interest statement was found in the publicly available original paper.
Reference
Labbe D, Gilbert F, Martin N. Impact of Olfaction on Taste, Trigeminal, and Texture Perceptions. Chemosensory Perception. 2008;1:217–226. doi:10.1007/s12078-008-9029-x
