This fundamental research could provide crucial knowledge of how consumers sense food for a food industry constantly organising the building blocks of new food formulations.
"There is a need for the food industry to know whether such cognitive processes on food perception have similar effects in classical/familiar and new/unfamiliar products," explained lead author David Labbe from Nestlé Research Centre.
The new research, published on-line ahead of print in the journal Food Quality and Preference (doi: 10.1016/j.foodqual.2006.04.006), investigated the olfactory responses of ten women (average age 45) on the perceived bitterness of a familiar (bitter cocoa) and an unfamiliar (bitter milk) drink.
Two different flavours were added (vanilla and cocoa) in three different amounts (none, medium, high) and the women asked to score the drinks in terms of bitterness, sourness, sweetness and body. Tasting was done with and without noseclips.
When the women tasted the beverages with the noseclip, it was found there was no perceived additional taste to the beverage due to the addition of vanilla or cocoa.
Without the noseclip however the cocoa flavouring in both beverages was associated with an enhancement of the bitterness, while the vanilla flavouring was linked to an increase in sweetness.
"This study is further evidence of the influence of olfaction on taste perception in complex matrices," said Labbe - the link between olfaction and taste has already been reported.
In addition to this, the novelty of this research came from extending the experiment with addition of bitter-tasting caffeine to the vanilla-flavoured milk.
While the vanilla did enhance sweetness, it also rather unexpectedly was associated with an increase in perceived bitterness, say the researchers.
These observations, say the researchers, suggest that the degree of familiarity for the beverage may be an important factor in determining taste-olfactory interactions.
"The pleasant familiar vanilla note may therefore have induced a positive hedonic expectation, which was not fulfilled by the unfamiliar milk beverage's bitter taste. Based on these statements, the unfamiliar bitter milk beverage was probably judged unpleasant by tasters and the combination between this product and vanilla flavouring may have increased the product's unfamiliarity and consequently its unpleasantness.
"The subjects may have associated unpleasantness with bitterness, thereby boosting the perceived bitterness when the unpleasant sensation increased with addition of vanilla flavouring," the researchers suggested.
During a second round of tasting, the researchers noted that the flavoured caffeinated milk beverages were perceived as significantly more bitter and less sweet than drink the first round of tasting.
"Our results suggest that taste-olfaction integration is product dependent and related to food experience," concluded Labbe.
The results have implications for tasting of commercial products since prior exposure to related products may affect the perceived taste and olfactory sensations of the new product, said the researchers.
Previous research into taste has revealed that the human tongue has about 10,000 taste buds with five taste sensations: sweet, bitter, and umami, which work with a signal through a G-protein coupled receptor; salty and sour which work with ion channels.
Contrary to popular understanding, taste is not experienced on different parts of the tongue. Though there are small differences in sensation, which can be measured with highly specific instruments, all taste buds, essentially clusters of 50 to 100 cells, can respond to all types of taste.
Taste buds (or lingual papillae) are small structures on the upper surface of the tongue that provide information about the taste of food being eaten.