How the sensation of "hot" develops
April, 2010: Hot, fiery tasting foods are becoming more and more popular. However, up until now there has been little research on these kinds of chemesthetic sensory impressions. A Polish research group pursued the question as to how the hotness of chilli develops when added to various foods, and in what way it alters the perception of other sensory attributes.
“First there is a burning sensation in the throat and back of the tongue. Then the sensation expands to the whole tongue and palate, and moves along the edges to the tip of the tongue. The sensation ends on the buccal mucosa especially around the inside of the lips. Simultaneously the original fiery burning sensation evolves into a persistent feeling of numbness” – such is the description given by test subjects when having tasted food highly seasoned with chilli powder.
That may sound dramatic, but it has a bright side; more and more consumers have come to enjoy the hot of spicy foods. Eliza Kostyra of the Faculty of Human Nutrition and Consumer Sciences at the Warsaw University of Life Science (WULS) - an ESN member - states that, ”When asked about their preference for the piquant, lovers of spicy foods indicate that the hotness gives food an extra dimension; there is more variety, the food is more interesting, and tastes better.”
The perceived sensation of hotness belongs to the chemesthetic stimulation system. This is a separate system, and behaves differently than the gustatory and olfactory ones. Chemesthetic sensations are perceived via temperature and pain receptors; they develop at a slower rate than do smells and tastes, last much longer and have slower rates of decay. Chemesthetic sensations are more persistent, and may cause strong sensitisation and desensitisation effects. Furthermore, the sensation of “hotness” varies qualitatively over time, and depends partly on the food context in which it is experienced.
The goal of Eliza Kostyra’s and her fellow researchers’ study was to get to the bottom of these phenomena. In the course of this study, the researchers served chicken-, tomato-, and mushroomsoup and -sauce models to a panel of six sensory experts. Each pair of the soup and sauce models contained the same basic components. All the models had the same level of salt (0.6%). They were seasoned with three different amounts of commercial chilli powder evoking low, medium and high pungency levels. Subsequently, the panellists rated the intensity of “hotness” in predetermined discrete time intervals; they also rated the intensity of other main taste/flavour components in the test products.
Study leader Eliza Kostyra underlined that, “A deciding advantage of using model soup and sauce matrices as carriers is that they were complex enough to be able to be compared to other “real” food preparations on the one hand, and on the other hand, they were simple enough that the variability could be precisely controlled for the purposes of the experiment. Whereas previous studies of the chemesthetic effect and its impact on taste have mostly been researched using aqueous sol
utions, the results of our experiments can be easily carried over to real-life situations.”
Which effects become evident?
The sensation of maximal intensity of “hotness”, as well as its length before the sensation began to slowly dissipate, and the length of the lingering sensation of “hotness” as it dissipates were all measured. The results depended on the amount of chilli that was used, as well as on the type and resulting complexity of the carrier (kind of soup or sauce).
It was found that the perceived chilli hotness was consequently more intense in the soups than in the sauces. Kostyra says that, “It may be that the starch content and resulting higher viscosity of the sauces impeded the contact of the chilli with the receptors.”
Variations in pungency intensity also affected the perceived flavours of the model samples. With the equal amount of chilli added, the flavour of the chicken soup and sauce were perceived as considerably hotter, with a longer lasting “after-burn”, than the tomato and mushroom soups and sauces. The variations of intensity were less pronounced when small to middle amounts of chilli were added.
The perception of the leading flavour attributes – chicken, tomato, and mushroom – were influenced to some degree. The attributes were slightly suppressed when chilli levels were increased. The degree of suppression varied depending on the model product. The effect was much stronger in the tomato samples than in the two others. This flavour-suppressing effect was much more evident in the soups and depended on the kind of flavour in the sauces. The intensity of the acidic taste in tomato soup changed in a non-linear manner: a sharp decrease was observed by the smallest addition of chilli (0.03%), and there were further decreases the higher the level of chilli. The same sequence of changes was observed in the tomato sauce, albeit to a lesser degree. However, the intensity of slightly bitter taste that is typical for soups and sauces made from dried mushrooms remained essentially unaffected.
Kostyra noted that, “Although the salt level was equal in all samples (0.6%) there were surprisingly dramatic differences in the perception of saltiness of the no chilli control samples. The addition of chilli reduced these differences: the more the chilli, the smaller the difference in saltiness”. At any rate the study’s leader concluded, “the hotness of chilli has only a moderate effect on leading flavour attributes. This agrees with the results of other researchers.”
The interactions between chilli-pungency and various taste/flavour qualities indicate the complexity of intra- and intermodal effects of hot spices on the senses when the spices are added to various foods. Because of the changing perception of the pungency quality over the time in which the food is consumed, these effects are even more variable.
Faculty of Human Nutrition and Consumer Sciences,
Department of Functional Food and Commodity Science,
Warsaw Agricultural University,
Kostyra E, Baryłko-Pikielna N, Dąbrowska U
Relationship of pungency and leading flavour attributes in model food matrices – temporal aspects
Food Quality and Preference
Volume 21, Issue 2, March 2010, Pages 197-206