Thursday 28 June 2018

All in good taste

This article is about our sense of taste, and mostly about some of the weird molecules that can make tastes beyond the usual four; bitter, salty, sweet and sour. To start with, here is a description how we taste things.

Whenever food goes into your mouth, it gets dissolved by the water in your mouth and goes into your taste buds. Each type of taste bud is tuned to a certain common molecule. When the right molecule goes into those taste buds, it binds to and opens ion channels, which are proteins on the membranes of body cells that they use to make an electric charge which travels to the brain. Sweet taste bud cells, for example, are mainly activated by sugars. A salty taste is mainly activated by positive sodium ions(Na+). Sour is activated by protons(H+), which show the presence of acid. There are many known compounds which make a strong bitter taste.

There are other chemicals that make more unusual and harder to identify tastes. This article is not only about the classical four tastes, but I will also describe some of the other, stranger, tastes, the ones that make food the widely varied and complicated thing it is.

Soy sauce has a lot of umami taste.
The first of these unusual tastes that I am going to explain is umami. Umami, or 'savoriness' should be considered one of the five basic tastes, but since it was not discovered by western scientists until recently, it is usually not counted. Food with a lot of umami taste includes tomatoes, soy sauce, meat stock(broth), some seafood and many fermented foods. One chemical that makes the umami taste is monosodium glutamate(MSG), which is often added to food in Chinese resuraunts to make the food taste better. There is a common belief that MSG is dangerous and causes symptoms like headaches and other kinds of discomfort, but scientific tests have found no evidence to support this. MSG is, in fact, a perfectly normal and healthy substance for flavouring, made out of molecules that are very common in food. It is no more harmful than salt.

The ghost pepper, one of the hottest chillies.
The next taste can be considered more of a sensation. It is spiciness, which is in many foods and usually comes from chili pepper. The spiciest substance in the world is capsaicin, because it is the cause of spiciness. This taste is unlike the normal five tastes in that the normal tastes were evolved by humans, but spiciness was evolved by chili peppers, probably to stop certain mammals from eating their seeds. The active ingredient, capsaicin, can also deter fungi, so it might have evolved for both purposes. The way capsaicin works is that it binds to and opens a certain type of ion channel, which is in the mouth and skin of mammals. This ion channel is otherwise only activated with heat, acid or other kinds of damage to the skin, and it sends a signal to the brain saying that the skin is being burned or heated. This is why spicy food makes a burning sensation when you eat it or touch it for too long. One interesting thing about spiciness is that it only works in mammals. This might be because wild chili peppers are dependent on birds spreading their seeds.

There is another taste which works exactly the same way as spiciness, except that the receptors that sense heat or burning are not activated, and a different receptor, which is normally triggered in cold conditions, is activated instead. This makes a cooling sensation, even if the food itself is not cold. This taste is referred to as coolness. Peppermint and spearmint are some of the things that have this taste.

Another neat taste-related thing is the influence of miracle berries, a type of berry native to Africa. Miracle berries are a kind of fruit which, if you chew on the berry and spit the seed out, changes the taste receptors in your mouth. In the juice of the miracle berry, there is a protein called miraculin, which has two sides; one that binds to the sweet taste receptor cells, and one that triggers the sweet receptor if it is in an acid. Since acid usually triggers only the sour taste receptors, miraculin can make anything sour, like lemons, taste sweet instead. The effect of miracle berries lasts for about 30 minutes. I have tried some miracle berries from a tree in a community garden I used to live close to, and the effect feels very odd. Miraculin is sometimes regarded as a sweetener, but it is not one. It only changes one taste into another.

The last taste effect is the strange effect caused by paracress, also called the 'toothache plant', a widely cultivated plant that is grown for ornamental and medicinal purposes. When its flower buds are chewed up, or rubbed onto the gums, it makes a bitter grassy taste, and soon after it makes a very strong sour, tingling and numbing sensation in the mouth, which lasts for about ten minutes. I have tried one of these before, at a herb farm, and because of this I can understand why they are sometimes called 'buzz buttons' or 'electric daisy'. The effect is very apparent. It is caused by a local anesthetic called spilanthol which is in the juice of the flowers and can be absorbed through the lining of the mouth. Like one of its common names suggests, the 'toothache plant' can be used to stop the pain caused by toothache because of this anesthetic. It is often grown for this purpose.

That is my list of 'unusual tastes'. There are many more of these that I left off this list, because they would make it too long. It makes sense that there are so many tastes like this, because how would seafood, paprika or even peppermint be able to have such an unusual effect on the mouth with only sourness, saltiness, sweetness and bitterness?

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