Certain odours can trick the brain into eating less salt or sugar

Obesity in adult populations in France has increased from 8.5% in 1997 to 17% in 2020

^{Source: Ligue contre l’obésité}

With obesity rates steadily increasing, reducing the amount of sugar and salt in food, whether at home or in ready-made meals, is high on the list of priorities. One solution may lie in food odour. Flavour not only includes the taste that we perceive through our taste buds—salty, sweet, sour, bitter, umami—but also the odours perceived through our nose. These two perceptions are unified by the brain, and that is what the researchers have set out to study.

Odours that entice the brain

Flavour involves the combination of taste and odour (or aroma)

Researchers at the Centre for Taste and Feeding Behaviour (CSGA) in Dijon have made a surprising discovery: we can use odours to trick our brains. For example, adding vanilla to your food activates the olfactory receptors in your nose, making food taste sweeter than it really is. Add unsalted peanuts and your food will seem saltier. This phenomenon is called Odour-Induced Taste Enhancement, and it's not just a chemical process, it is also cultural. In France, vanilla is associated with sweetness, but contrary to all expectations, lemon is the aroma most associated with sweetness in Vietnam. This cultural difference suggests that the influence of odours on taste perception is linked to repeated exposure to different aromas over the course of our lives. 

Portrait Charlotte Sinding, a question of good taste (nouvelle fenêtre)

Charlotte Sinding is a junior researcher who joined INRAE five years ago to study the use of odours to reinforce the perception of taste. Working at the Center for Taste and Feeding Behavior, she uses a panoply of instruments — from MRIs to olfactometers — to investigate what goes on deep within our brains.

A phenomenon that's even more effective in obese people

A recent study shows that taste enhancement is even more effective in people suffering from obesity. In this study, 38 obese and 43 normal-weight participants tasted 13 sweet drinks—apple juice, cocoa, water—and 4 savoury drinks—pea soup, water—containing different taste-enhancing odorants: vanilla, strawberry or lychee to enhance sweetness; smoked bacon and smoked garlic to enhance saltiness. While, overall, the reinforcing odour phenomenon was more efficient in obese people than in normal-weight people, apple juice produced the most remarkable results. In fact, 83% of the obese participants perceived the apple juice containing vanilla flavour to be sweeter than the same juice with no added odorant—compared to only 61% of the normal-weight participants. Even more surprising, among these 83%, 37% perceived the apple juice with vanilla odour as sweeter than the apple juice with an extra 33% sugar added! For normal-weight people, only 6% perceived the apple juice with vanilla as sweeter than the apple juice with 33% more sugar. But why? While researchers have observed structural differences in the brain areas that process Odour-Induced Taste Enhancement in obese people, the brain mechanisms that explain this difference in perception are still under study.

These results could be of great benefit to the agrifood industry, since they could lead to the identification of promising spices or natural odours that could help reduce sugar and salt content in our food, improving food quality.

^{Reference: Christopher Aveline, Cécile Leroy, Marie-Claude Brindisi, Stéphanie Chambaron, Thierry Thomas-Danguin, Charlotte Sinding, Influence of obesity on saltiness and sweetness intensity enhancement by odors, Food Quality and Preference, Volume 102, 2022, 104685, ISSN 0950-3293, https://doi.org/10.1016/j.foodqual.2022.104685}