Let’s talk about the two experiences felt by the trigeminal nerve touch, astringency and pungency.

As mentioned before, astringency is a rough texture that is dry and not smooth. The substance that causes astringency is generally tannin, also called tannic acid, which is a phenolic compound.

This type of substance consists of 3 to 5 carbon rings and is just the right size to surround two or more salivary protein molecules and combine with them, allowing the unconnected proteins to stick together into clumps and adhere to food particles and various food particles.

The surface at which the surface is located increases the surface friction, and we feel astringency.

Tannin is also a defensive chemical substance in the plant world. Tannin is most commonly found in unripe fruits. The purpose is to prevent the seeds from being eaten when they are unable to germinate. The outer skin of the fruit usually also contains a large amount of this substance to protect the fruit.

As for quickly becoming infected with mold and becoming rotten.

Another thing that can be felt through touch is pungency.

Foods that can induce pungency, including spicy spices and spicy vegetables, contain highly active pungent substances and work in different ways.

For example, the spiciness in garlic is different from the spiciness in chili.

They are described below.

The spiciness in garlic is that defensive substances are produced only when the tissue is damaged and enzymes and substrates that are not usually in contact are mixed together, similar to this, such as mustard and onions, horseradish and horseradish.

Processing can reduce the spiciness of these foods because enzyme activity decreases when heated.

These defensive substances are all sulfur-containing compounds, which are mostly small, light, hydrophobic molecules composed of about 10 to 20 atoms.

Once food is ingested, these molecules easily spread throughout the mouth and nasal cavities. They stimulate the nerve endings in the mouth and nose, and then the nerves send pain messages to the brain.

Speaking of this spicy feeling, we must mention the Allium genus of the Liliaceae family. The plants in this genus are quite individual. The onions, garlic and leeks in this family have completely different tastes.

Intact onion cells only have the flavor precursor substance alkylcysteine ??sulfide, of which four species have been found so far. They are present in the cytoplasm, and the enzyme is in the vacuole, so the onion surface looks very mild, but when cutting the onion

, the cells are damaged, the enzymes in the vacuoles come into contact with the flavor precursors, and hydrolyze them into thiopropionaldehyde-S-oxide. This compound is the tear-inducing factor, which can make people cry, and it can also cause heat and burning.

feel.

Garlic, a member of the Allium genus of the Liliaceae family, is well-deserved for its status in the world of Chinese gourmet condiments.

On the surface, it looks warmer than onions, but when you chew it, you will find a colorless and odorless flavor precursor substance (scientific name is S-allyl-cysteine ??sulfoxide, a kind of onion flavor precursor).

) Under the catalysis of enzymes, allicin is produced. Although this substance is pungent and smelly, it is hard to let go and has endless aftertaste.

There are also Brassica plants, such as cabbage, mustard, sprouts, etc., and their defensive precursors are glucosinolates.

Glucosinolates are different from the precursors of onions. In addition to sulfur, they also contain nitrogen. Therefore, the flavor compounds produced are mainly isothiocyanates. These flavor precursors and products also have pungent and bitter tastes.

There are many types of glucosinolate precursors, and their combinations have unique characteristics.

Therefore, cabbage and mustard greens have similar tastes, but also have unique flavors.

The spiciness in peppers is a defensive component stored in plant tissues. Damaged tissue or cooking cannot increase or decrease the spiciness, similar to that of ginger, black pepper and Sichuan peppercorns.

Such chemicals are alkyl amides.

These molecules are large and heavy, containing about 40 to 50 atoms, so they generally do not volatilize from food to regulate our nasal cavities, but mostly act in the mouth.

These substances can bind to the receptors of sensory neurons. When the receptors are activated, they transmit a burning sensation, so when you eat chili peppers, you feel a burning sensation.

Mammals, especially herbivores, are allergic to capsaicin, but birds are not, so peppers can be eaten by birds and then spread their seeds.

Relying on this method, peppers have thrived in the mountains of South America for tens of millions of years. Unfortunately, this defense mechanism became a special attraction when it encountered humans, Sichuan people to be precise.