Ever since the acceptance of umami as the fifth taste in the 80s, there has been research and debate into the existence of the sixth taste. In fact, in recent years, scientists have proposed a number of possible tastes. Along the way, research has revealed even more about foods and flavors.
Is There a Sixth Taste?
The five basic flavors are salt, sweet, sour, bitter, and umami, or savoriness. These basic tastes interact with receptors in the mouth, giving specific flavor sensations. However, not all flavors can be described in simply these five terms, which leads chemists and food scientists to search for more basic tastes.
In order for a flavor to meet the standard of a “basic taste”, researchers must prove that:
- The taste has a unique chemical signature
- The taste triggers specific flavor receptors
- People must be able to distinguish the flavor from others
The final criterion is often the sticking point: not everyone experiences flavor the same way, and not everyone describes their taste experiences in the same way. To judge taste, flavors are often measured against a reference flavor; for example, the sweetness of a food is judged against a reference point of pure sucrose. However, many “taste” candidates lack similar absolute references, making subjective measurement even more complicated.
Currently, there are several flavors competing for “basic flavor” status that would elevate them to the taste status. Here are some of the top contenders:
Piquancy or Pungency
Nobody would disagree that the heat or spiciness of food isn’t a unique taste. This taste is found in chilis, mustards, curries, and other foods considered “hot” or “spicy”. Adding pungency as a taste may seem like a natural choice, but it is held back for two reasons:
- Reference measure. While we have the Scoville scale for measuring the heat of chili peppers, we do not have an absolute reference measure for the pungency of food. Unlike pure salt or pure sucrose, we don’t have an absolute chemical reference for the taste of heat.
- Receptors. The perception of spice/heat/and pungency reaches the brain through a huge range of different carriers. Eating hot foods triggers taste receptors, but also triggers somatosensory fibers in the oral cavity, transmitting a sense of “heat” in a similar way to touching something hot, rather than tasting something hot.
The truth is, pungency may simply be too broad a term. Most people would agree that the spiciness of a hot sauce, the spiciness of a mustard, and the spiciness of a curry are substantially different. Our vocabulary for spiced, seasoned, and hot foods limits our ability to describe these tastes, so we may actually be searching for several different basic tastes instead of one.
Richness or Kokumi
Another candidate is kokumi, a sense of richness in food. Like umami, this taste was discovered by scientists in Japan, and is frequently present in Asian foods. Kokumi is as much a feeling or physical sensation as a taste; it’s the flavor of added richness and roundness that enhances other flavors. It is naturally present in aged and fermented foods, and explains why aged wine, cheese, and soy sauce, or slow-roasted meats and vegetables, taste better than their quickly-prepared counterparts.
While kokumi is a readily identified flavor, and has been tracked to the specific Calcium Sensing Receptor, it is not yet considered a basic taste because it has not been traced to a specific molecule, Instead, the kokumi sensation is activated by naturally occurring glutamyl peptides in aged foods. Interestingly, a recent study appears to show that cats are more sensitive and responsive to kokumi, while humans are more sensitive and responsive to glutathione.
Kokumi has been isolated and is available in a powdered form as a flavor enhancer. For the short term, at least, we seem to be treating it as a seasoning rather than a basic taste.
Fattiness or Oleogustus
It seems natural that humans would have a specific taste for fatty acids, since they are such an important part of our diet. Generally speaking, we perceive the fattiness of food as a physical sensation affecting mouthfeel, creaminess, or smoothness. However, scientists have determined that fatty acids derived from triglycerides have a unique flavor, and we do have fat flavor receptors.
The reason that oleogustus has not yet made the ranks as a (sixth) basic taste is because not everyone can taste or distinguish this flavor. Most recent studies show that only about half of people are able to readily distinguish fatty acid flavor samples from other flavors.
Interestingly, the isolated fatty acid compounds have an unpleasant taste, leading many people to classify them as “bitter” rather than “fatty”. Like all the other tastes, in low concentrations it enhances food, while in high concentrations it is regarded as unpleasant.
Starchiness or Carbohydrates
Until recently, scientists believed that humans could not detect the taste of carbohydrates. These flavors break down so quickly in the mouth that scientists believed that the flavor associated with carbohydrates is the flavor of sweetness or sugars. But new evidence shows that people have a unique response to flavors they would describe as “starchy.” In the East, this flavor is associated with rice, while in the West it is associated with bread. When test subjects are given compounds that specifically block sweet taste receptors, they are still able to detect and describe foods that contain long-chain carbohydrates.
While the ability of test subjects to separate and identify starchiness from sweetness makes it a strong candidate for being a taste, scientists have not yet identified any receptors specifically associated with this flavor. Research is ongoing.
Instead of asking “Is there a sixth taste?” we may soon start asking “how many tastes are there?” In fact, we may move away from the subjective questions of taste and flavor altogether. The real answer seems to lie in the direction of chemistry: we have unique receptors for calcium, triglycerides, peptides, amino acids, long-chain carbohydrates, antioxidants, and more. A better understanding of our taste receptors will eventually allow us to craft whole new flavor combinations and sensations, transforming the foods of the future. To be part of the exciting frontier of food innovation, you need the right talent. Contact grapefrute for expert recruitment in food and beverage science.