[Reading Science] The Secret of the Sixth Taste Perceived by the Tongue

'Jibangmat' is described as a greasy taste. It must be added in the right amount to blend with other flavors and create a synergistic effect.
[Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jonghwa] The tongue can perceive five basic tastes: sweet, sour, bitter, salty, and umami. However, recently, there has been a claim that the tongue can sense an additional taste, drawing attention as a potential "sixth taste of the tongue." What kind of taste is this?

Humans have genes on their tongues that allow them to perceive tastes, which help identify the nutrients needed by the body. Sweetness distinguishes carbohydrates that provide energy essential for survival, umami identifies proteins, and saltiness detects sodium, which is important for maintaining the body's fluid balance, metabolism, and blood circulation.

Bitter taste serves as a warning to avoid toxic substances in food, while sourness indicates whether food has spoiled and helps identify vitamins. Carbohydrates are consumed through rice and snacks, umami through cheese or meat, protein through meat and eggs, and sodium through salt. Consuming sodium in amounts exceeding the body's needs can harm health.

In addition to these five tastes, the tongue is said to perceive "fat taste." Fat taste is close to a "greasy taste." For example, regular milk tastes richer and more savory than low-fat milk, and eating meat with both lean and fatty parts is more delicious. When a small amount of fat taste is present in food, it enhances the flavor.

However, while a moderate amount positively affects taste, excessive fat or fat taste alone does not produce a pleasant flavor. When the greasy taste of fat becomes strong, it causes discomfort and reduces palatability.

In 2012, Professor Nada Abumrad's team at the University of Washington in the United States published research in the international journal Lipid Research, showing that the tongue can perceive "fat taste" in addition to the five basic tastes. The team discovered that a receptor called "CD36" on the taste buds of the tongue recognizes fat molecules and distinguishes fat as an independent taste.

Supporting research was also published. In 2015, Professor Richard Mattes' team at Purdue University in the United States gave 1,000 participants six solutions labeled as sweet, sour, bitter, salty, umami, and "fat taste," a greasy flavor, and asked them to distinguish the tastes.

As a result, participants could clearly distinguish sweet, sour, and salty tastes but could not separately identify the other three tastes. However, in a second experiment focusing only on bitter, umami, and fat tastes, participants were able to distinguish each taste. In experiments involving foods combining all six tastes, participants also identified fat taste separately.

Can the fifth taste, 'umami,' be followed by 'fat taste' as the sixth taste?2
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In a paper published in an international journal, the research team argued that the Latin term "oleogustus," meaning "oily and tasty," should be recognized as the sixth basic taste. However, participants described fat taste as an "unpleasantly strong and irritating taste." The oily and tasty flavor appears as an effect when mixed in appropriate amounts with other foods.

The issue with fat taste is that it is "not well perceived." People who do not perceive fat taste well tend to gain weight easily. There are individuals who perceive fat taste strongly and those who do not, and those with higher levels of CD36 on their tongues perceive fat taste more acutely.

Such individuals feel fat taste strongly even with a small amount of fat and tend to avoid fatty foods. Conversely, people with lower CD36 levels on their tongues do not perceive the greasy and unpleasant taste of fat well, leading them to consume larger amounts of fatty foods and gain weight.

Research and debate are ongoing in the academic community regarding whether fat taste should be recognized as the sixth basic taste. Regardless of whether fat taste is officially recognized as the sixth taste, it quickly becomes familiar and dulls the tongue's sensitivity. This means that regularly consuming foods high in fat may lead to weight gain, so caution is advised.