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In the sensory analysis of virgin olive oil we work on the olfactory and taste sense. The olfactory sense is the one that tells us in the first place if it is a fresh oil or an old or defective oil.
The olfactory receptors are the responsible to perceive aromas, and they are found in the nostrils. Inside the nostrils are lined with a mucosa called the pituitary and is divided into two areas:
- The lower area, called the red pituitary,is highly vascular and therefore takes on a reddish hue. Its function is to heat the air that enters the nose. It is also responsible for cleaning the air of any particles or impurities. It lacks proper olfactory function.
- The upper area is the yellow pituitary. It is the region responsible for the sense of smell and has specialized cells and is where the olfactory receptors are found. This upper region would be responsible for the sense of smell.
To stimulate the olfactory receptors found in the upper part, the substances have to be volatile, not very heavy. This means that they must give off vapors that can penetrate the nasal passages, and that they have to be soluble in water so that they dissolve with mucus and reach the olfactory cells.
These olfactory cells transmit a nerve impulse to the olfactory bulb and from this to the olfactory centers of the cerebral cortex, which is where the sensation of smell is appreciated and interpreted.
The aroma in virgin olive oil is perceived as a result of the interaction between numerous volatile compounds and their corresponding olfactory receptors.In general, we can say that the aroma is the dominant perception of any food.
The sense of smell begins its operation, as we have said before, when it is stimulated by the molecules that are in the air we breathe or by volatile substances contained in the food that are taken to the nose or mouth.
The olfactory sense begins with the nose and includes other parts of the head and brain.The nostrils, smell receptor neurons, the olfactory bulb and the brain are involved in the olfactory process, which is where the process of identifying an aroma is carried out.
Olfactory sensations are not fixed or long-lasting. During an olfactory cycle of 4 or 5 seconds corresponding to a slow inspiration, a progressive increase in sensation is registered and then a slow disappearance.
For a substance in solution to be perceived as aromatic it is necessary it to be volatile and to have a minimal weight, and this is the reason why volatility influences as much on its aromatic power.
On the contrary, the main compounds in virgin olive oil, as we have commented on several occasions, are triacylglycerols, but these, due to their weight,it is not possible to be smelled. Hundreds of thousands of differentiated stimuli are perceived. However, we are unable to catalog since we do not have as many qualifiers in the language as would be necessary for it.
The characteristic aroma of virgin olive oil is the result of a complex mixture of volatile compounds that mainly includes aldehydes, alcohols, ketones, hydrocarbons, furans and esters. However, the first two represent qualitatively and quantitatively the most important fractions of volatile compounds in virgin olive oil. These compounds are responsible for the green aromatic notes characteristic of virgin olive oil. The volatile compound profile of an oil depends mainly on its quality, and its profile is more complex as its quality is lower.
In other words, newly obtained, high-quality virgin olive oil has a simpler volatile compound profile than low-quality ones, which present a greater number of volatile compounds responsible for unpleasant odors and which come from different enzymatic and chemical routes.
Filmina extracted from the Virgin Olive Oil OnLine Tasting Course. ESAO