More about Thermal Tasters

More about Thermal Tasters

At the Sensory Science Group Conference last week our PhD student, Qian Yang (Candy) gave us an update on progress with her research. I have summarised the main points here.

What is a Thermal Taster?

Cruz and Green found that warming the tongue of some people using a special thermode device can evoke sweetness, while cooling it can evoke sourness and/or saltiness. Some individuals can experience both heat-related sweetness and cold-related saltiness, while others only experience one or the other. These people are known as Thermal Tasters (TTs). People who don't perceive any ‘phantom' taste due to heating or cooling are known as Thermal non-Tasters (TnTs).

Previous research has indicated that TTs may perceive some stimuli as more intense than TnTs. First steps were to determine if there was a difference in detection thresholds between TTs and TnTs. Candy screened over 200 respondents for their TT status and classified them into 3 groups: Thermal Tasters (TTs), Thermal non Tasters (TnTs) and uncategorized (Uncat). TTs detected a taste sensation on both heating and cooling of the tongue, TnTs did not perceive a taste, and Uncat were inconsistent in their reporting throughout the classification trials. The most common taste sensations reported were metallic, sweet, bitter and sour. Amazingly, TTs formed 27% of the study population!

Candy went on to determine the detection thresholds of 124 of these people for each of seven taste, aroma and mouth-feel stimuli. The results showed that sucrose was the only stimulus for which TTs and TnTs showed a difference in detection threshold: the TTs were more sensitive. This indicates that the greater sensitivity of TTs at supra-threshold concentrations reported by earlier researchers does not hold at detection level. This is not too surprising, as we know that we perceive things at threshold and above threshold, by different mechanisms.

Do TTs Perceive Stimuli More Intensely at Supra-threshold Concentrations?

105 screened respondents participated in the supra-threshold study. Subjects rated the intensity of five series of taste, odour and trigeminal sensations, namely sweet, salt, bitter, acid, ethyl butyrate and capsaicin (heat) plus the intensity of cool and warm.

Results showed that TTs rated cool and warm sensations more intensely than TnTs. In terms of the taste, odour and trigeminal sensations, TTs tended to rate intensities higher than TnTs, although there was no statistically significant difference for any one stimulus.

How does TT Status Relate to PROP Taster Status?

PROP taster status has long been recognized as a marker of differences in sensitivity of individuals, particularly to bitter products. It is genetically determined, and as part of trying to understand the origins of TT status, Candy's study investigated if there was any relationship between the two phenomena.

She found that the two were generally independent of one another. However, some PROP tasters may have their sensitivity enhanced if they are also a thermal taster, whereas others (those who are especially sensitive to PROP) will not have the same enhancement.

How will our TT Group React to your Products?

Candy's respondent pool was screened in part from Sensory Dimensions' consumer panel database, so we now have a group of people whom we know have TT status. If you are interested in investigating how this group reacts to your products in relation to a non-taster group then please contact us. Or if you just want more details of any aspects of these studies then please get in touch.