“Science of Taste: Sour”

When life gives you lemons, make lemonade.

Next time you drink a glass of lemonade, think about where the main ingredient came from.

The lemon is a quintessential part of many dishes. It adds character to the classic Maldivian combination of garudhiya and rice. It adds a tang to desserts and is used to bring out the flavor in a number of dishes in many cultures. But where did the lemon originate from? Historians are at a loss for the answer but the closest link is to a region of Northwestern India.

While lemons are famous for its characteristic sour taste, it’s not the only source of the sour flavor. Let’s not forget about passion fruit, Bilimbi (Bilimagu in Dhivehi), fruits such as orange and grapefruit, tamarind, green mango, and kumquats. Sour foods also include fermented vegetables such as kimchi, sauerkraut, sourdough bread, yogurt, vinegar, and the list goes on.

The sour taste of these foods isn’t everyone’s cup of tea though. Individual preferences mean that not everyone likes kimchi or sauerkraut because not everyone has the same palate. Some of these foods are definitely an acquired taste and this can be attributed to the evolution of our taste.

The purpose of detecting sour taste is to prevent consumption of acidic food. Therefore, it was only associated with un-ripened fruits or spoiled foods. However, spoiled or not, yogurt and cheese are globally popular foods in today’s current age.  Acids are what all these various aforementioned foods have in common.

You might recall being taught the tongue map back in your elementary school days. The map claims that each taste has its designated receptors in specific areas of the tongue. Recently, this myth has been debunked. Turns out, the entire tongue can detect all five identified tastes pretty much equally. Out of all the five tastes, scientists know the least about how sour taste works. Nevertheless, researchers have identified PK2DL1 as the taste receptor responsible for sourness.

A study conducted in 2006 found that PK2DL1 can also be found along the length of the spinal cord in nerve cells that surround and extend into the central canal. Researchers suspect that since PK2DL1 detects sourness or acidity, these receptors might be responsible for monitoring the pH of the cerebrospinal fluid. This finding was significant because PK2DL1 is part of a group of proteins called “polycystic-kidney-disease-like ion channels” and as per its name, mutations in some of these proteins are connected with kidney failure. Since the cause of failure is still unknown, this discovery could be a thrilling and unforeseen ticket to combatting severe kidney disorders.

With this information in mind, health-conscious individuals ought to add sour foods to their diet. However, if you’re reluctant to do so because you dislike sour foods, it might be because of your childhood diet.  A study investigating the effects of early experience on sweet and sour preferences in children found that the earlier sour foods are introduced to children, the more likely they will grow up to prefer sour tasting food.

Unlike the inborn fondness for sweet tastes, newborns reject sour tasting food. You’ve probably seen this from your own child or in the many viral YouTube videos of babies making grossed out faces after tasting a lemon. So if you’re one of those people who never understood the international trend of kombucha tea known for its distinctive sourness, the answer probably lies in the lack of sour foods in your childhood food regimen.

If we were to all collectively examine our current diets, the large preference for sweet and salty foods can be observed.  Hence, the dietary neglect of sour and bitter tastes are a shame. Like most things in this world that come in complementary and opposite pairs, sourness balances out the sweetness. It can also give a “rounded taste”, as the Thai’s apparently call it, to really hot spices. This balance of tastes can either be described as an art or a science.

Our sense of taste is more complex than we estimate it to be. From childhood dietary preferences affecting adult taste perception, to fighting kidney disease and balancing taste, sourness has been greatly under-looked. Prime example being the characteristic sour tasting lemon colloquially being used as a term for disappointment.

As they say, when life gives you lemons, make lemonade.

Words by Afaaf