Posted by Eric Troy on 17 Jun 2015 15:36
Bitter is one of the tastes that you can distinguish by the taste buds on your tongue, along with sweet, sour, salty, and unami. It was once though that you could only taste bitter with the back of your tongue, but we now know that bitterness can be registered by all parts of the tongue where taste buds reside. However, there are more bitter taste receptors on the back and sides of the tongue.
Bitter is a taste that we associate with toxic substances. Therefore, a strong bitter taste may also cause a gag reflex, which occurs as a protective mechanism. Bitter tastes stimulate the brain through the gloosopharyngeal nerve, which is also associated with the gag reflex.
Foods that are more alkaline, with a higher pH, have a more bitter flavor to us. Plants contain alkaloid components, many of which can be highly poisonous. These alkaloids have nitrogenous bases and are often present as salts of acetic, oxalic, lactic, malic, tartaric, citric, or other acids. Alkaloids can have very strong physiological effects in human beings. A well-known poisonous alkaloid is stryhnine. Others, however, such as caffeine are stimulants, or even, like morphine, analgesic. They can be quite beneficial, at times.
As well, metallic compounds, glycosides, and peptides are experienced as a bitter principle. The number of molecules that we perceive as bitter is very high, and these molecules show a wide variance in structure. The amino acids histidine, methionine, valine, arginine, phenylalanine, tryptophan, leucine, and tyrosine have a bitter taste. Lysine and proline are both sweet and bitter.
Since many sour foods are also bitter, bitterness is often confused with sourness. Many common cooking tips meant to remove bitterness from foods or recipes are actually countering sourness, and vice versa. The best way to counter bitterness is with sugar, which helps balance out bitter flavor.
Although bitterness is disliked when the taste is too strong, or when not expected in a food, it is often thought to be an important part of the overall flavor profile of certain products. This is true in chocolate, for example. A bitter component is considered an integral part of many beverages such as beer, wine, tonic water, tea, and coffee. Bitterness is such an important part of many cocktails that a special kind of mixer called "bitters" has long been used, the most famous of which is Angostura.
Bitter tastes are often accompanies by a type of mouth-feel called astringency, which is felt on the tongue and the mouth itself. This is also sometimes referred to as tannin, since tannins tend to cause this feeling. This is the sensation of "mouth puckering" or having your tongue dried out and made to feel "rough" that comes from eating a bitter food or drinking a bitter beverage. Although we often describe it as if it were a taste, it is actually a sensation. Cranberries are bitter and astringent (and also sour), and are one of the best ways to experience this feeling. Astringency is associated with bitterness often enough that many people mistake it for bitterness itself.
Astringency is important in both tea and wine. It is thought that similar compounds are responsible for the astringency in both, collectively referred to a tannins, hence the designation given above. Among wine, it is more prevalent in reds, where the astringent components come principally from the grape skins and seeds. Some compounds, such as anthocyanins, may enhance astringency without actually contributing to bitterness on their own. In wines, this feeling of astringency which coats the mouth is sometimes described as "slippery." You may have seen the word "brisk" or "briskness" used by tea companies to describe their tea. This term refers to astringency. Both lemon juice and milk added to tea help counter this astringency.
You Either Love or Hate Bitter Tastes?
Since some people will passionately embrace a certain bitter food, and others will absolutely reject it, not matter how it is prepared, many people think that some people simply love bitter flavors and other people hate them. This is not true. One person may appreciate the bitterness in a certain food or beverage and then despise the overly-bitter taste of another. For example, a person who seeks out bitter chocolate may still refuse to eat Brussels sprouts because they are too bitter. This probably has to do with the complexity of how bitter compounds are tasted. There are likely many mechanisms for perceiving bitterness. There may be multiple sites for bitter reception on the tongue, and how hydrophobic a certain compound is may affect the level of perception. Also, other components also present with bitter compounds may enhance the bitter taste. It could be possible, then, for a person to be a "super-taster" of the bitterness in one food, while finding it tolerable or even pleasant in another. In other words, Brussels sprouts may taste more bitter to one person than to another.
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