Students Explore Tastes with Special Kit Developed by Ajinomoto

Elementary and junior high school students in Yokosuka City, Kanagawa Prefecture, are learning about the five basic tastes — sweet, salty, sour, bitter, and umami — through hands-on activities designed to promote healthy eating habits.

Exploring Flavors

In February, students at Uraga Elementary School carefully sipped green tea from paper cups, their expressions serious.

"Hold it in your mouth for five seconds and see what you can taste," instructed Taeko Inamura from Ajinomoto Co's Global Communications Department, Science Group.

For many students, savoring tea so deliberately was a first-time experience. Afterwards, they chose from the following options: "sweet," "salty," "sour," "bitter," "umami," "I can taste something but don't know what," or "no taste at all."

Next, students sampled liquids from five pouches and recorded their impressions in the same way. Each pouch contained one of the five basic tastes, but the students were not told which. Finally, they tasted green tea again to compare.

Inamura, who oversaw the lessons, explained, "Identifying each taste is surprisingly difficult — even about 20% of adults get it wrong. After checking the answers [for the five pouches] and trying the tea again, children often notice sweetness and umami in addition to bitterness."

The lessons also included activities such as tasting gummies while holding their noses and comparing miso soup with and without umami seasoning.

Partnership for Food Education

This hands-on program is part of a partnership between Ajinomoto, Kanagawa University of Human Services, and the Yokosuka City Board of Education. Based on an agreement signed in April 2024, they have continued research on the health, fitness, and lifestyle habits of elementary and junior high students in the city. 

This year, they are conducting experiential food education classes at Uraga Elementary, Obaradai Elementary, and local junior high schools.

Discovery of Umami

Taste is sensed by taste buds on the tongue, which transmit signals to the brain. For many years, the four basic tastes were considered to be sweet, salty, sour, and bitter.

In 1908, Japanese researcher Kikunae Ikeda discovered a fifth taste, umami, and developed it into the glutamate-based seasoning Ajinomoto®, which later became widely used around the world. Spiciness and astringency also contribute to flavor but are detected through pain or temperature sensations, so they are not classified as basic tastes.

Taste Kit

The five pouches used in the program are a taste kit developed based on sensory tests conducted for Ajinomoto product developers. Concentrations were repeatedly adjusted so that 95% of people could correctly identify the taste in each pouch. The compositions are as follows:

• Sweet: sucrose (3.2%)
• Salty: table salt (0.5%)
• Sour: citric acid (0.16%)
• Bitter: caffeine (0.08%)
• Umami: Ajinomoto (monosodium glutamate, disodium inosinate, etc.) 0.16%

Two years were spent refining the concentration, liquid volume, and pouch design while confirming safety and ensuring no allergens were included. 

Kaneyuki Tsutsumi, Senior Producer at Gakken Group, who oversaw the educational materials, noted: "We also designed the pouches so children could open them safely without risk of injury."

Understanding Taste

Taste serves as an important survival signal: sourness can indicate spoiled food, while bitterness may signal toxins. Children's dislike of bell peppers, for example, is a natural, instinctive reaction. Adults, with more experience, can enjoy bitter flavors like coffee, but children often avoid them.

Inamura explained, "Teachers and parents often try to force children to eat nutrient-rich foods like carrots or bell peppers or label them as picky eaters. However, there are biological reasons behind food preferences. It's not always necessary to view children's likes and dislikes negatively."

Factors Affecting Taste

Diet has a strong influence on taste perception. At Uraga Elementary School, many children described miso soup without umami seasoning as tasting like "shellfish." This area is a fishing town, and many children live with their grandparents, having miso soup at least once a day.

Inamura explained, "It seems that many families make miso soup with shellfish. We haven't fully investigated, but it's clear that their diet is reflected in their sense of taste."

Other factors also influence taste. After sweating during sports, the body may be less sensitive to salt. Smokers often find bitter tastes less noticeable.

Compared with adults, children generally prefer sweeter and saltier flavors, meaning the minimum concentration at which they perceive these tastes is higher. However, after the taste lessons, some children reported tasting sweetness in unsweetened tea, showing that awareness can heighten taste sensitivity.

The Power of Umami

Miso soup with umami seasoning was rated "delicious" even at the same salt concentration, demonstrating that umami can reduce the need for salt. After the lessons, students began discussing flavors during lunchtime, saying things like, "This has umami!"

Taku Kuroiwa, Associate General Manager of Ajinomoto's Global Communications Department, Science Group, said, "Lessons that teach how to connect taste and language are rare. If children can express their sensory experiences in words, even once, they become more aware of what they eat in daily life."

Around the world, food companies are coming under close scrutiny. Obesity has become a common health issue not only in wealthy, developed countries but also in developing nations, where economic disparities and changing food cultures are contributing factors. 

Processed foods that are often high in salt, sugar, and fat, such as fast food and snacks, are often consumed simply because they taste good. Food companies that focus on making products "delicious" are seen as partly responsible for accelerating the obesity problem.

Kuroiwa added, "That's why studying taste scientifically and teaching children to understand it is also our responsibility."

By engaging with taste and reflecting on food, children can rediscover the enjoyment of eating and develop skills to maintain a healthy diet. Ajinomoto hopes to expand the use of its "food education tools" nationwide, promoting the message: "Eat Well, Live Well."

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This report is published in cooperation with Ajinomoto, a logo partner of Japan 2 Earth.

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Author: Mika Sugiura