Although there is no accurate word for it in English, umami is considered one of the five basic tastes we can perceive. And what better way to explore the science behind this taste than by savoring a delicious Japanese mushroom stew?
Since our section’s inception, we’ve offered our readers scientific recipes featuring various flavors and textures. However, we have not yet explained in depth what taste is and how we perceive it. What distinguishes between sweet and salty foods and between bitter and sour tastes? Is there a connection between them? What is umami anyway? And can taste sensations be created artificially?
The Japanese have already answered at least one of these questions. Recently, there have been reports on the internet about a device developed by scientist Homayi Miyashita from Meiji University in Japan, which allows the artificial creation on the tongue of the variety of flavors that we experience every time we taste different foods. To understand how this is possible, we’ll focus on the umami taste, which was first defined in Japan, and we will illustrate it through a mushroom stew.
Let’s start with the main ingredient - mushrooms. On the cutting board we have mushrooms, garlic, and onions | Ostranitsa Stanislav, Shutterstock
What do you need?
3 tablespoons light soy sauce
½ teaspoon dark soy sauce
1 teaspoon sugar
1 tablespoon rice vinegar
¼ cups water
1 teaspoon cornstarch
2 tablespoons oil
500-600 grams of portobello mushrooms, cut into cubes
3 thin slices of ginger, ground
3 chopped garlic cloves
4 green onions (the white part only), cut into thin slices
1 teaspoon of Szechuan pepper (those who don’t like spicy foods can leave it out)
up to 8 units of dried chili, soaked and sliced
1 cup of diced red pepper
½ teaspoon sesame oil
1 tablespoon roasted peeled peanuts
What do you do?
To make the sauce, mix the soy sauces, sugar, vinegar, water, and cornstarch in a small bowl.
Heat one tablespoon of oil over medium heat in a wok or pan. Add the mushrooms and fry until they caramelize and the liquid evaporates. Transfer to a bowl and set aside.
Heat another tablespoon of oil in the same wok, add ginger, garlic, green onions, Szechuan pepper, and dried chili, and fry for about a minute. Be careful not to burn the spices. Add the red pepper and continue to fry while stirring.
Add the cooked mushrooms, turn up the heat, and stir well.
Mix the sauce well and add it to the stew. Stir everything together in quick movements and remove from the heat.
Add the peanuts and sesame oil.
And Now To The Science
Legend has it that the Chinese philosopher Confucius once proclaimed, “Everyone eats and drinks, yet only few appreciate the taste of food.” The sense of taste evolved as an evolutionary mechanism to assist us in evaluating the food we consume. A bitter or sour taste may signify poisonous plants or food rich in spoiled protein. In contrast, sweet and salty tastes generally signify a nutrient-rich food source.
Humans have the ability to distinguish between five primary tastes: bitter, salty, sour, sweet, and umami. These flavors help us assess the quality and safety of the food we consume and detect signs of spoilage. The process of identifying taste involves communication between cells in the oral cavity and nerve cells that transmit signals to the brain. Scattered on our tongue are papillae - the tiny bumps visible on the tongue. Each papilla contains between fifty to one hundred taste buds - specialized cells with receptors that are activated upon contact with chemical compounds present in the food and beverages we consume.
There are four types of papillae. The most prevalent type does not directly determine taste but rather helps to grip food on the tongue and mediates sensations of temperature, texture, and pain. The remaining three types of papillae are the ones responsible for enabling us to distinguish between tastes. Within these papillae, specialized taste buds are divided into various types of cells that react to the chemical compounds present in the food or drink, transmitting signals to the brain. The brain then processes these signals and creates the sensation of taste.
An Essential Source of Information
In scientific terms, bitter and sour tastes are classified as “aversive tastes” because we generally tend to avoid them. On the other hand, the other tastes - sweet, salty, and umami - are classified as “appetitive tastes,” and we generally tend to enjoy them. Taste preferences likely evolved because the taste system is the final decision point at which we decide whether to consume a particular food. The principles that guide our eating habits include evaluating whether the food is energy-rich, whether it is toxic, and whether it provides the body with protein.
The sweet taste is a basic need for humans. Even in early infancy, babies react to sweet food with a smile, while bitter foods make them scrunch up their face. The sweet taste indicates that the food contains a lot of energy or calories, which throughout human evolution has been a very positive sign since we need energy to survive. However, in modern times, since food in wealthy countries has become readily available, overconsumption of sweet foods has become a global problem, manifested in obesity and diseases such as diabetes.
The salty taste suggests that the food contains minerals important for the body’s functioning, such as sodium or potassium. Salt is not only responsible for the salty taste, but it also helps reduce bitterness and enhance sweetness. However, excessive consumption of salt has also become an important issue in public health debate due to the potential health problems that may arise from excessive intake of certain minerals.
The sweet taste signals that the food is rich in energy, but excessive sugar consumption in the modern western diet has become a health problem. A girl licking sweet batter | Jacob Lund, Shutterstock
The Newest Taste
Unlike the first four tastes, known to us since the dawn of humanity, umami was identified as a basic taste only a little over a century ago. The scientist who identified it was the Japanese researcher Kikunae Ikeda, who tested a soup stock composed mainly of seaweed. He called the taste he found umami, which means “very tasty” in Japanese. In practice, umami is not very tasty on its own, but it enhances the taste of foods.
The umami flavor comes from the amino acid L-glutamate, or monosodium glutamate. The amino acid is one of the products of protein breakdown that are naturally found in foods such as meat, milk, mushrooms, and tomatoes. Foods rich in free glutamate, such as ripe tomatoes, are considered especially tasty. This is also why the taste of aged meat is richer than that of regular meat - the aging process involves protein breakdown, which leaves many free amino acids in the meat.
The umami taste is enhanced in the presence of salt due to the interactions between the different taste receptors. This is why many people like to season tomatoes with salt. The umami taste also enhances sweetness and balances the bitter and sour flavors. Similar to sweet and salty tastes, the attraction to umami serves an evolutionary purpose, as our bodies need protein to function properly.
The source of the umami flavor is in the amino acid L-glutamate, which is found in foods such as meat, milk, tomatoes, and mushrooms. Mushroom stew stir-fried in a wok | Ostranitsa Stanislav, Shutterstock
In Matters of Taste and Smell
The taste is primarily influenced by the tongue, but the sense of smell also contributes to the perception of taste. The sense of smell operates in two ways during eating: direct absorption of volatile compounds that emanate from the food and reach the front of the nose, and absorption of volatile compounds that are released from the food during chewing and reach the nose through the back of the mouth. We can detect thousands of scents, and our brain combines the information from the olfactory receptors and taste buds to create a complex sense of taste.
However, this is still a partial picture. Another sensory system greatly influences how we experience hot and spicy foods and cold or burning foods. In the human brain’s frontal cortex lies the trigeminal nerve, which controls, among other things, the sensation in the face and movements for chewing, biting, and swallowing. The cells in the trigeminal nerve react to chemical stimuli in the mouth, throat, nose, and even the eyes. Therefore, exposure to a strong mint scent, for example, evokes a sensation of coolness, while wasabi creates irritation in the nose and tears in the eyes.
At the ends of the cells in the trigeminal nerve, there is a family of ion channels, which are proteins that allow atoms with positive or negative electrical charges to enter or exit the nerve cells, thereby enabling the transmission of nerve signals. These channels are also responsible for detecting touch and temperature - a discovery that earned the scientists who uncovered it the 2021 Nobel Prize in Medicine. These ion channels react, among other things, to capsaicin, the active ingredient in hot peppers. Therefore, foods such as wasabi and horseradish stimulate a sensation of warmth and burning that we perceive as spiciness. A device that stimulates taste is capable of reproducing these sensations.
By mixing five conductive gels with different flavors, new flavors can be created. The flavor generator device developed by Miyashita | From the research article
Creating Artificial Tastes
Understanding the chemical processes involved in taste perception is also the basis on which Miyashita developed the taste-generating device mentioned at the beginning of the article. The device contains five conducting gels, one for each taste, so a specific taste can be amplified or weakened by changing the intensity of the current passing through its gel. When the five gels are mixed, different flavors are obtained depending on the ratio between the gels in the mixture, similar to how LED bulbs of various colors can be created by combining red, green, and blue colors.
Of course, one can ask what the point is in using this flavor device. After all, if one wants the taste of an apple, one can simply eat an apple. But according to the developers, if we can create our favorite flavors without the foods that created them, we can, for example, recreate the taste of our favorite chocolate snack without the high amount of calories it contains. It is somewhat reminiscent of what Willy Wonka did in the book “Charlie and the Chocolate Factory” when he developed a stick of chewing gum that recreates the taste of a satisfying three-course meal of tomato soup, beef, and blueberry pie.
Of course, nothing compares to the real eating experience, no matter how accurately the device replicates the taste. Mechanical actions such as chewing and swallowing, the sense of smell, and other senses provide our brain with important information, where taste is part of a whole multisensory experience. All that is left for us is to enter the kitchen, cut, fry, saute and season, and bon appetit!
A video depicting how the flavor generator works