Tasting Does Not Occur in the Tongue Alone

However, aromatic expectation does not always correspond to the experience that develops during consumption. An orthonasal aroma may be strong and then weaken inside the mouth. Alternatively, it may appear limited before consumption but be released progressively during chewing.

A professional evaluator should therefore distinguish among:

• Aroma before consumption.
• Aroma during chewing.
• Aroma after swallowing.
• The final aromatic aftereffect.

Combining these stages into one early judgment may produce an incomplete evaluation that fails to capture flavor development over time.

Fourth: Retronasal Olfaction and Its Central Role in Flavor

Retronasal olfaction occurs when volatile aromatic compounds are released from food inside the mouth and travel through the pharynx to the nasal cavity and olfactory region during chewing, swallowing, and exhalation.

Several factors contribute to this process:

• Breakdown of the food structure.
• Mixing food with saliva.
• Changes in the sample’s temperature inside the mouth.
• Movement of the tongue and jaw.
• Duration of chewing.
• The characteristics of fat and water.
• Swallowing.
• Airflow from the mouth toward the nasal cavity.

Although the olfactory system receives these compounds, people often experience their identity as though it existed inside the mouth. This is why many people describe aroma as “taste.”

Neuroimaging studies have shown that the route through which an odor reaches the olfactory system influences its processing. Odors delivered retronasally may be perceptually referred to the mouth differently from odors received through the nostrils. The neural response may also vary according to whether an odor is food-related or non-food-related.

Orthonasal and retronasal olfaction therefore activate the olfactory system but perform overlapping rather than identical perceptual functions:

Fifth: Why Does Aroma Seem Like Taste?

This phenomenon is known as the oral referral of odor. It means that the brain attributes retronasal aroma to food inside the mouth rather than experiencing it as originating in the olfactory region.

When a sweet beverage containing vanilla aroma is consumed, two different signals occur:

• The gustatory system detects sweetness.
• The olfactory system detects vanilla aroma.

Because these signals appear at approximately the same time and are associated with the same food source, the brain integrates them into a unified experience. The result in everyday awareness is not separate sweetness and odor, but a “sweet vanilla flavor.”

The degree of congruence between odor and taste affects the strength of this integration. Experimental research has shown that congruence is important for the oral referral of retronasal aroma. An aroma normally associated with sweetness may integrate with sweet taste more readily than an aroma that is not associated with sweetness in previous food experience.

These relationships may be acquired through learning, repetition, and culture. When a particular aroma is repeatedly paired with a particular taste, the brain learns the relationship. One component may subsequently predict the other or influence its perceived intensity.

This effect is not necessarily identical among all individuals. It may vary according to experience, food environment, language, age, training, and cultural context.

Sixth: The Flavor Object as a Perceptual Construction

The concept of the flavor object can be used to describe the unified perceptual entity constructed by the brain from different sensory signals associated with one food or beverage.

People do not normally experience a separate list stating:

• There is sweetness.
• There is vanilla aroma.
• There is warmth.
• There is viscosity.
• There is a fatty sensation.

Instead, they experience one entity, such as “a warm, sweet, smooth, and rich vanilla cream.”

This entity results from the integration of several components:

Where:

• F: perceived flavor.
• G: gustatory signal.
• R: retronasal olfaction.
• O: orthonasal olfaction and aromatic expectation.
• S: somatosensory information and mouthfeel.
• T: temperature.
• C: chemical sensation.
• M: memory and acquired experience.
• E: expectation, context, and emotion.
• I: neural and perceptual integration.

This formula is not a finalized clinical equation for measuring flavor. It is a conceptual model illustrating the diversity of flavor’s sources.

The brain does not combine these elements through simple arithmetic. It may enhance, suppress, or reinterpret individual components according to congruence, context, previous experience, and the evaluator’s physical and psychological condition.

Seventh: The Brain Constructs Flavor Rather Than Receiving It Ready-Made

Gustatory, olfactory, and somatosensory signals travel through specialized neural pathways. They then converge within brain networks involved in recognition, integration, memory, emotion, value assessment, and decision-making.

The insular cortex contributes to taste processing, while olfactory areas process odors. The orbitofrontal cortex also participates in integrating taste, aroma, texture, and the motivational value of food.

Functional magnetic resonance imaging studies have shown that odors delivered through the mouth can activate regions associated with smell, memory, emotion, and sensory integration. These include the piriform cortex, orbitofrontal cortex, insula, amygdala, and hippocampal regions. This helps explain how retronasal aroma becomes part of an experience that appears taste-like.

A study published in 2019, using an animal model and neural inactivation techniques, found that inactivating gustatory cortex impaired the expression of preferences associated with retronasal odors without producing the same effect on orthonasal odors. This finding suggests a distinctive functional relationship between retronasal olfaction and taste-processing circuits.