Taste the palate

How Humans Detect Flavors

What causes people to dislike certain foods while others love them? This question has puzzled chefs like me, troubled food producers, and frustrated many parents dealing with picky eaters. Food and drink preferences—whether it's adding milk or sugar to tea or coffee, or choosing ketchup, vinegar, or mayonnaise with fries—are partly shaped by social and cultural influences, as well as by habit. However, there is growing evidence that our food preferences are also influenced by individual variations in taste perception. Since taste plays a significant role in flavor perception, these individual differences could help explain personal flavor preferences.

The human tongue can distinguish between four primary tastes: salty, sweet, sour, and bitter. Taste buds, which contain several taste cells, are located within taste papillae on the surface of the tongue. When we consume food or drink, taste molecules dissolve into saliva. Taste transduction occurs when these chemicals contact receptor sites or channels located at the tips of taste cells, in the correct orientation.

It was once believed that different areas of the human tongue responded to specific tastes. While there are slight differences in sensitivity across the tongue and palate, all tastes can be detected from all regions of the tongue that contain taste buds. Taste cells, like olfactory receptor neurons, are continually replaced throughout life, making the taste system particularly resilient to ongoing exposure to stimuli.

Some people are particularly insensitive to one or more tastes. Approximately 15-30% of people cannot detect certain tastes at all, and these individuals are referred to as "non-tasters." However, the taster/non-taster frequency varies among ethnic groups. There is also variation in sensitivity to bitterness. People who can taste extremely bitter flavors are known as "supertasters," while those who find bitter flavors moderately intense are known as "tasters." It's important to note that a supertaster is not necessarily better at tasting than a non-taster; the term simply refers to their heightened perception of certain bitter compounds.

In fact, there are many different bitter-tasting compounds. Recent studies have identified approximately thirty genes encoding receptors responsible for recognizing bitter compounds, suggesting there may be up to thirty receptors for bitter taste. Different receptors may be responsible for detecting different bitter compounds. For example, compared to non-tasters, supertasters perceive sweet, sour, salty, and bitter compounds more intensely, as well as other mouth sensations such as the burn from chili peppers, black pepper, ginger, and alcohol.

Environmental factors also influence likes and dislikes. For instance, nausea can create an aversion to foods consumed shortly before the episode, even if the food did not cause the nausea. It is generally accepted that some changes in taste occur as a function of age, though these effects appear to be minor.

Science has played a crucial role in advancing our understanding of flavor perception. Research techniques have improved significantly over the past few years, with the invention of machines such as the atmospheric pressure chemical ionization mass spectrometer (APCI-MS) to measure aroma release from foods and beverages, and the liquid chromatography-mass spectrometer (LC-MS) to assess some of the textural properties of food. However, the most sensitive and valuable flavor-measuring "machine" is still people, who can describe the flavors they perceive as they eat.

Flavor Challenges

For a chef, the variety in taste sensitivity poses a potential challenge. If a chef has a low sensitivity to salt but a high sensitivity to acidity, this will likely affect how they season a dish. How will a customer with a low sensitivity to sourness but a high sensitivity to salt respond to such a dish? Even more importantly, what happens if the chef cannot detect bitterness—how will a supertaster respond to their dish?

These variations may help explain why different people prefer the cooking styles of some chefs over others. Additionally, a closer look at the data reveals another interesting fact: the same individual may respond differently to the same flavor solution on different test days.