Aroma And Retronasal Smell: Two Routes Into Flavour

What Are Orthonasal And Retronasal Smell?

When we smell the aroma rising from a cup, volatile molecules enter through the nostrils. This is the orthonasal route. Aromas released while food is in the mouth can instead travel through the connection between the upper throat and the nasal cavity. This is the retronasal route.

There is no second nose inside the mouth. Both routes reach the olfactory area high within the nasal cavity. The distinction concerns the direction from which molecules arrive and the moment of the food experience at which they do so. Smelling a food from outside and encountering its aroma during eating do not share the same entry conditions.

These terms help describe the difference between noticing an herb's smell during preparation and experiencing its aroma within a food. They identify two encounters with the same ingredient: a smell entering the surrounding space, and an aroma participating in what happens in the mouth.

How Do Taste And Aroma Meet In Flavour?

Sweetness, sourness, saltiness, bitterness and umami are taste qualities. Descriptions such as fruity and floral generally belong to smell. Texture, temperature and chilli pungency contribute other information to the same encounter. Flavour names the integrated experience in which these contributions come together.

An aroma seeming to occur somewhere in the mouth does not establish that taste receptors detected it. Retronasal smell is closely associated with eating and with the mouth, so ordinary conversation readily calls it taste. The scientific distinction explains the two sensory routes behind that familiar expression.

Why Does Airflow Matter To Aroma?

Releasing an odour molecule and bringing it to the sensory area in the nose are different events. Transport takes place between them. Air moving with breathing affects the direction in which volatiles around the mouth can travel. An ingredient's list of compounds therefore cannot, by itself, account for its aroma experience.

Ni and colleagues investigated this question with a physical model in 2015. They used computed-tomography images from one healthy person's upper airway to construct the model. Inward and outward flows interacted differently with the region behind the mouth. In the model, outward flow helped volatiles from that region join the passing airstream.

This was not an experiment measuring people's enjoyment of food, and the model represented one airway geometry. It nevertheless makes a useful detail tangible: transporting a molecule towards the olfactory area involves both the shape of the surrounding space and the direction of flow. Aroma connects an ingredient with human anatomy through this physical journey.

What Did A Vanilla Experiment Reveal About Timing?

In 2017, Kakutani and colleagues used apparatus that synchronised odour delivery with participants' breathing. While participants rated the sweetness of a sucrose solution, vanilla odour was delivered through the mouth or nose, before or after drinking. The investigation concerned the route and timing of a smell as well as its presence.

Ten participants entered the analysis of the first experiment. Vanilla delivered retronasally after drinking increased perceived sweetness ratings. In the second experiment, analysed for eight participants, the presentation order changed and the same increase was not observed. Six people took part in both experiments, so these were not wholly independent participant samples.

The finding belongs to the vanilla–sucrose combination and the controlled apparatus. The authors also discuss the possibility that people assigned some odour intensity to the only rating scale provided, which concerned sweetness. The study cannot establish that a smell always makes a dish sweeter. It raises a more precise question: how does the order in which sensory information arrives participate in its integration?

An Aroma Description And A Whole Flavour

A fruity aroma is an odour description. It does not, on its own, identify a compound or its concentration. Equally, a laboratory's list of volatile compounds does not describe a finished food's entire sensory character. Presence in a material, transport to the nose and perception within an experience are connected but distinct questions.

That distinction enriches culinary language. We can describe a pepper-based hot sauce through aroma, sourness, pungency and texture, then consider how those qualities meet within a dish. Aroma is a moving layer of an encounter at the table: it begins with ingredients, follows the path of air and gains meaning alongside the other senses.

• The distinction between umami and aroma
• Documented examples of peppers in desserts
• From a sensory description to a judgment of taste