The history of chili peppers is a story in which culture, tradition, passion and science are intertwined. We can imagine it set in crops, such as in vegetable gardens, greenhouses, open fields of any rural area on the planet; in kitchens all over the world, not only as an ingredient of the cuisine of the poor but also of gourmet recipes, and then in the laboratories of sensory analysis and neuroscience researchers.
Chili peppers originated in Bolivia and parts of Brazil. From there they have been propagated throughout the Americas by birds, immune to the action of capsaicin.
The Aztecs were the first to incorporate chili peppers into their food and religious rituals, and the cultivation of this plant is documented as early as 5500 BC.
From the new continent, the chilli pepper arrived in Europe with Christopher Columbus, and was later spread to Africa and Asia, where in some countries it is now part of the local culinary tradition, as also happened in many regions of southern Italy.
What are the reasons for its widespread diffusion?
Certainly, on a botanical and agronomic level the rusticity and ease of adaptation to different soils and climatic conditions.
To this, however, may be added:
- the attractiveness of colour. Red is known to increase blood pressure and to stimulate the appetite, warmth, conquest.
- the pleasantness of the sensation of spiciness, a ubiquitous characteristic found in foods all over the world even if preferences change according to geographical areas. In Asian and Central American countries there is a predilection for chilli, pepper, ginger while in western areas for carbonated drinks, wine, onions and horseradish. In addition, it should be remembered that more than 25% of the world population (between Asia, South and Central America and Europe) consume chili peppers daily.
The consumer is more curious and demanding every day. In Italy, the Calabrian pepper is in great demand. Gourmets prefer the Habanero originally from Mexico, very spicy but also fragrant and aromatic. Extremists favor the Naga Morich, the Naga Viper or the Carolina Reaper. The latter, considered the spiciest in the world, is originally from South Carolina (USA) and obtained from the cross between the famous Habanero Red and a Naga Morich from Pakistan. It has a characteristic sweet and fruity flavor, with hints of cinnamon and chocolate. Its extraordinary spiciness makes it practically inedible for an unaccustomed palate.
What are the substances that cause this burning sensation?
Capsaicin and capsaicinoids, which are incredibly stable alkaloids, remain unchanged for a long time even after cooking and freezing. They are produced as secondary metabolites from chili peppers, probably as a deterrent against some mammals and fungi. They are synthesized from two amino acids, phenylalanine and valine. There are eleven of them in nature. The part richest in capsaicin and therefore spicier is that of the placenta (the tissue that supports the seeds) located in the center of the fruit where the capsaicin glands are located while the seeds are covered only on the surface with capsaicinoids but are devoid of them inside.
Pure capsaicin is hydrophobic and colorless, appearing as a crystalline or waxy solid. Together with dihydrocapsaicin, it is one of the alkaloids responsible for most of the "hotness" of chili peppers.
The presence of the aliphatic chain, linked to the vanilloid ring, makes capsaicinoids not soluble in water but rather in ethyl alcohol and even more in substances of a lipid nature.
Hence the use in recipes of both savory and sweet foods with a significant fat component, both as fresh and powdered ingredients (e.g. pepper oil, pepper taralli, chili pepper cheeses and salami, chilli sauces, spreadable creams, chilli pralines, chocolates and pepper honey).
It is also understandable why, to neutralize the burning sensation, the most effective methods may be to drink a sip of whole milk or yogurt or to ingest a spoonful of oil; chewing on buttered bread can be decisive, as can a touch of cheese. Not being very soluble in water, drinking water is not a relief.
How does the spicy sensation define its origin?
It is a chemically induced sensation called chemesthesis, which does not involve the activation of the gustatory and olfactory receptors but causes the activation of the receptors sensitive to physical stimuli.
These are non-specific pain receptors that may be excited by mechanical, thermal and/or chemical stimulation present in the buccal and pharyngeal cavities and, to a lesser extent, also in the nasal cavity. They are small-calibre (weakly myelinated to unmyelinated) free nerve endings of the trigeminal nerve or fifth cranial nerve. A multipurpose nerve that enriches the perceptive system with its different sensitivities, tactile, thermal, pain and chemical, the already complex sense of smell and taste. And when the chili turns into a burning sensation and the menthol into freshness, some fibers of this nerve that are sensitive to heat or cold, offer their receptors to molecules neither hot nor cold, which deceive them.
The best known and recognizable chemesthetic sensations that contribute to the description of the flavor of a food are: spiciness induced by the capsaicin contained in the chilli pepper, freshness associated with menthol, astringency associated with tannins and the electric sensation, also called tingling, induced from Sichuan pepper.
Sichuan pepper is the archetype of chemesthesis, capable of generating a dense and intense electric tingling followed by a slight lemon aroma and inducing a slight numbness of the oral cavity, in particular of the tongue, without however causing the typical burning sensation of chili peppers.
The compounds responsible for the spiciness stimulate those thermo-nociceptors of the type that binds capsaicin (vanilloid receptor - VR1) which is also activated by high temperatures.
The information related to pain moves more slowly (from 2 to 30 m/sec) than from other neurons, for which the transmission speed can reach 100 m/sec. Therefore, it is observed that the chemesthetic sensations in the mouth are perceived more deeply than the basic gustatory sensations and the sensation that is generated is not immediate but is much more persistent.
How can the spicy displeasure become a pleasure?
Neuroscience are dealing with how our brain responds to certain/specific sensory stimuli, distinguishing the good from the disgusting, and usually preferring spicy and sweet, bitter and sour. As for the receptors of basic tastes, it should be remembered that the principle of sensitivity also applies to chemesthetics that varies from individual to individual in relation to genetic factors, to exposure to molecules responsible for perceptions, to the physiological state of the individual (age, disease).
In cases where the level of spiciness exceeds the threshold value of the individual, the adaptive manifestations of the subject are aimed at the expulsion of substances that produce irritation, such as diffuse sweating, lacrimation, redness, rhinorrhea, increased body temperature, salivation, and inflammation of the epidermis (in particular of the nasal mucosa).
So, in cases where stimuli are excessive in intensity and persistence, they can interfere with other perceptions, masking to the point of undermining the acceptability by the consumer. In cases where the spicy level is lower than the threshold value of the individual, the response becomes acceptable up to liking it and can be seen in:
- enhancing the flavour for the increase of:
i. salivary secretion (with increased action of digestive enzymes and flavour enhancers) which increases palatability, with an effect on the creaminess and adhesiveness of fats or oiliness of oils in sauces;
ii. the persistence and amplification of accessory, gustatory, aromatic and tactile perceptions, as the overlap of the signals produces a kind of self-amplification due to the overexcitation of the perception.
- Neurotransmitters stimulation:
i. acceleration of the metabolic activity;
ii. production of endorphins (mediators of the state of pleasure and satisfaction) that act on our mood making us almost euphoric, no longer making us perceive the spiciness as painful, but as something pleasant.
Since the pain receptors make sure that persistent damage is not “forgotten”, and therefore a painful feeling is maintained for a long time even if the cause which provoked it is no longer present, it is possible that this effect favors the memory of the sensation of pleasure and satisfaction, induced by spiciness at the level close to that threshold of the individual.