Once peeled, the mandarin releases an intense aroma due to numerous volatile compounds. Among these prevail i terpeneshow limonene And linaloolresponsible respectively for the citrus and floral notes. These molecules spread rapidly in the air, stimulating the olfactory receptors and generating the typical tangerine smell. At home, when you place the peels on the radiator, heat accelerates the evaporation of terpenes and other volatile substances, quickly perfuming the environment surrounding: compared to other citrus fruits, such as i lemonsthe volatile molecules present in mandarin peel are “lighter” which is why they tend to spread more easily in the air.
The volatility of mandarin molecules: why the smell does not last long
One of the first times we hear of the mandarin is in a list of fruits offered in tribute to the emperor Dayubetween 2205 and 2197 BC, in a Chinese Encyclopedia entitled Yu Kung. In fact, it is believed that the mandarin (scientific name Citrus Reticolata) was domesticated in Southern China. Compared to other citrus fruits, such as grapefruit or orange, mandarin has a less adhesion between peel and pulpa feature that allows you to peel it easily without using a knife: this aspect makes it particularly practical and suitable for a quick snack. Once freed from the peel, it is released into the environment penetrating and unmistakable odor, the result of a complex mix of volatile substancesi.e. molecules that evaporate easily and diffuse into the air. Among these, numerous stand out terpenesorganic compounds responsible for the characteristic aromas and scents of many plants and fruits, such as limonene and linalool.
All these molecules, and many more in fact, quickly disperse into the air as soon as the mandarin is peeled, interacting with our olfactory receptors and generating the characteristic perception of mandarin scent. However, there is a downside: precisely because these molecules are highly volatile, they tend to evaporate quicklyreducing the persistence of the scent and aroma in the fruit itself during storage.
In fact, in a study reported in the International Journal of Food Science and Technology, we read that after a sensory evaluation by a panel of trained tasters, the flavor of mandarin was rated between good and excellent at harvest, but slipped to “fair” after 6 weeks of storage. This decline is linked not only to the loss of volatile compounds, but also to formation of new molecules resulting from biological processes, such as fermentation. Among these, we can mention theethanol el’alpha-pinenethe latter associated with an unpleasant odor, similar to that of mold, which ends up masking and counteracting the good scent of terpenes.
The differences between citrus fruit peels: why we put mandarin peels on the radiator
It may happen that at home one of our relatives, a grandmother or an aunt, does not immediately throw away the mandarin peels, but places them on the radiator. A simple gesture, but which hides a small chemical explanation: the heat favors the evaporation of volatile substances contained in the peel, managing to perfume the room without the use of sprays or diffusers. But why is mandarin peel often chosen, instead of using other citrus fruits such as lemon?
According to what emerges from a study published in Frontiers, citrus fruits can be classified into three groups (“clusters”) depending on the volatile profilethat is, the type and quantity of volatile molecules contained in the peel. The mandarin (C. reticulata) is part of the first cluster, together with the Citrus aurantium (the’orange), and has a higher abundance of compounds non-terpenic aliphaticsmainly aldehydes and chain esters short.
In the second, intermediate cluster, we find for example the bergamot, Citrus bergamiawhile the lemon (C. limon) is instead part of the third group, also characterized by the presence of sulphured monoterpenoids (molecules derived from terpenes that contain sulfur atoms), which are often molecules larger and heavier compared to those contained in the mandarin peel, and this it could reduce its volatility: the heavier a compound is, the more it tends not to pass through the air, as if it had ballast attached.
