In Search of Flavor

By Bryan Quoc Le | 150 Food Science Questions Answered

A monk started to prepare his simple lunch of rice, vegetables, and broth. After meditating for hours, he grew hungry and wanted a delicious meal. He looked inside a wooden vat of fermenting miso made from soy beans and wheat that he had prepared the winter before. All that was left were dredges that had seeped through the bottom. Curiously, the monk decided to reach with a wooden spoon. As he raised the utensil to his mouth, the aroma wafted into his nostrils — toasty, caramel, and acidic. He brought the dark liquid to his tongue.

The taste was exquisite.

According to legend, Shinichi Kakushin was a Japanese Zen Buddhist monk who has been credited with introducing soy sauce to Japan in 1254 AD. While both Chinese and Japanese monks had been exchanging recipes for soy sauce across the Sea of Japan since 772 AD, it wasn’t until Kakushin serendipitously discovered a recipe for this particular shoyu soy sauce that the Japanese began their love affair with this universal condiment, whose bold flavor and high quality became revered over the current soy sauces available.

Buddhist practitioners and monastics alike were bound by the tenet of not deliberately harming living creatures, and so meals served in the Buddhist community became largely vegetarian, despite the fact that the Buddha himself prescribed no restrictions on meat intake. Plus, Buddhists were restricted in their consumption of certain herbs like garlic and onion, which led to a demand for a versatile seasoning that could add a punch of flavor to bland vegetarian fare. Kakushin’s discovery coincided with the spread of Zen Buddhism and its acceptance into both the aristocratic and military social circles. With this newfound prestige and wealth, temples were built across the island nation, which came with a great need for soy sauce. Soy sauce met the ticket, and monasteries became the de facto centers for soy sauce production and development.

Kakushin taught his nearby lay community as well as fellow monastics in the small town of Yuasa, Japan. As the popularity of this soy sauce recipe rose together with the widening influence of Buddhism in the country, the sauce became an integral feature of Japanese cuisine for Buddhists and non-Buddhists alike. Over centuries, the Japanese learned to distinguish the presence of a powerful, ephemeral flavor in soy sauce that had yet to be named — umami.

The Science of Soy Sauce

Soy sauce is traditionally made by inoculating a mash of cooked soy beans and toasted wheat with koji-kin, the hibernating spores of the mold Aspergillus oryzae. During the growth stage of the mold, mycelium spread into the crevices of bean and grain, exuding extracellular enzymes along the way. These enzymes are the key to unlocking flavor in the otherwise bland mash through the breakdown of proteins and carbohydrates. Proteins in both soy and wheat are especially rich in the amino acid glutamic acid, which is released by the mold-driven enzymatic digestion. Glutamic acid is arguablely one of the key flavoring components of soy sauce.

Concentrated salt brine is added to the fermenting mixture after three days, which causes the growing koji mold to burst open, release the remainder of its enzymatic payload, and accelerate the decomposition of proteins. The high salinity brine also protects the mash from undesired bacteria and yeast. The enzymes go to town on the remaining carbohydrates and proteins, and after several weeks, months, or even years, the mash is filtered to give a distinctly brown liquid rich in glutamates and salt. Together, the two make up the basic building block of umami flavor: monosodium glutamate, or MSG. This MSG-laced sauce became an important driver for the expansion of shoyu soy sauce as an essential ingredient for Japanese cooking and would allow its consumers to pick up on the presence of the yet-to-be-named umami in foods steeped in soy sauce and other umami-rich ingredients.

Kikunae Ikeda — The Father of MSG

However, while soy sauce has been used in Japanese cuisine for centuries, the realization that MSG was the source of the umami effect was only discovered in the last 100 years. Kikunae Ikeda, a Japanese professor of chemistry, began his journey to flavor stardom at the dinner table. Something of an early 20th century foodie, Ikeda was very much interested in the chemistry of taste. One night, after a long day in the laboratory, his wife decided to serve him a particularly delicious broth of miso. After cross-examining her about what she had done differently with the recipe, she explained that she had only added a bit more kombu seaweed, a seaweed traditionally used to flavor Japanese dishes.

The effect of the kombu made a tremendous impact on the Japanese chemist. It occurred to Ikeda that no one had yet identified this essential principle of taste that could transform a modest meal into one fit for a king. Professor Ikeda set to work on capturing that flavoring principle in his wife’s broth and uncovering its chemical secrets.

He began with one pound of high-quality kombu seaweed, which he could procure relatively cheaply from the local food markets and applied the basic steps of chemical discovery: extraction, separation, and purification. Just rinse and repeat, until all that’s left is the essential factor responsible for the desired effect — in this case, enhanced flavor.

After one year of endeavor, Ikeda was eventually able to isolate a few sandy brown crystals, which he quickly identified as monosodium glutamate due to its discovery back in the 1880s by German Nobel laureate and chemist Emil Fischer. Fischer himself only tasted glutamic acid alone and did not notice any enhanced taste perception.

In gustatory anticipation, he added the crystals to a bit of broth and sipped.


He had found the proverbial diamond in the rough, and it was MSG.

Ikeda named the magnifying flavor effect “umami” – a loanword for “pleasant savory flavor”. He went on to find a cheap route to MSG suitable for industrial production by cooking wheat, one of the key sources of glutamate for soy sauce, in concentrated acid. The acidic brew is neutralized with soda ash and the desired MSG recrystallized from the treated broth. He acquired patents in Japan, France, the United States, and the UK for his newly discovered process, which could churn out pounds of MSG in a matter of days.

To commercialize his efforts, Ikeda co-founded the Ajinomoto Company with Sabururosuke Suzuki II in 1908. Ajinomoto would eventually bring the infamous white crystals of umami to every corner of the world and earn billions in the process.

The Rise of Flavor Enhancers

Professor Ikeda’s breakthrough opened the flood gates for a new culinary concept — flavor enhancers. And the discoveries didn’t stop at MSG. Ikeda’s protégé, Shintaro Kodama, found another umami-boosting molecule (this time, from fish flakes), disodium inosinate in 1912. And many decades later, Japanese researcher Dr. Akira Kuninaka of Yamasa Shoyu Research Laboratories (a soy sauce company) isolated the umami enhancer, disodium guanylate, from yeast extract treated with koji enzymes. He also discovered its ability to synergize with MSG and disodium inosinate to greatly enhance the umami effect. This trio of compounds has been harnessed by Ajinomoto and other flavor companies as the basic building blocks of flavor. Broths, sauces, seasonings — really, anything savory under the sun — have been sprinkled with these near-magical compounds to boost up the bland flavors that resulted from the necessary heat treatment processes used by the food industry to extend food product shelf life and keep food microbiologically safe. Not to mention, these same compounds have been used to overcome the poor flavors of low-quality food ingredients as well.

But corporate and academic research into flavor enhancing agents hasn’t stopped. Even within the last decade, the emergence of the ‘kokumi’ taste principle is beginning to take root in the culinary and food industry world, based on Japanese research conducted in the 1980s. Kokumi is something of a mystery, even to flavor scientists, but has been described as ‘heartiness’. If umami is a spike in the taste graph that punches up the strength of sweet, sour, and salty, kokumi extends the enhanced taste effect for longer periods on your tongue. The major natural ingredient that imparts kokumi is glutathione, a compound found abundantly in yeast extracts, and is used to extend the staying power of the three main umami-enhancers to form a long-lasting orchestra of flavor. You can find these very same ingredients all wrapped up beautifully in those aluminum pouches of instant ramen seasoning.

The four horsemen of flavor enhancement (monosodium glutamate, disodium inosinate, disodium guanylate, and glutathione) have taken the grand stage in modern food ingredient formulation, becoming key players in almost any savory food imaginable. Both lucrative and in high demand, these cherished ingredients have become the de facto taste foundation on which savory foods are designed in the food and flavor industry. When perusing down the grocery aisle and inspecting the ingredients list, you’ll notice the nearly-foreign words ‘monosodium glutamate’, ‘disodium inosinate’, ‘disodium guanylate’, and ‘yeast extract’ in far more food products than expected.

Recent pushback against artificial ingredients by health-conscious consumers today, spearheaded by food advocates and clean eating gurus, has reduced the popularity of these ingredients to some extent. But the truth is that these four are here to stay, primarily because substitutes derived from natural sources just can’t go toe-to-toe with them on strength, intensity, or cost-effectiveness. While the food research community continues to excavate for more powerful flavor enhancers, food and flavor companies will go on including these umami and kokumi-intensifying ingredients in their products. The toolbox of flavor enhancers will simply expand to satiate the hunger of an ever-growing world population.

As a food product developer once told me, “People will say they eat for health. But really, their wallets say they eat for flavor.”

That’s something to chew on while eating a bowl of instant ramen.

Bryan Quoc Le | 150 Food Science Questions Answered

Bryan is the author of 150 Food Science Questions Answered (Rockridge Press, 2020) and a Ph.D. candidate in Food Science at University of Wisconsin-Madison studying the health effects of garlic and onion flavors. He received his B.S. and M.S. in Chemistry at the University of California, Irvine.  In another life, he walked 2,000 miles from California to Louisiana in six months, and learned that eating tuna and peanut butter every day was not meant for the average human body.  After he met his wife, he learned that there was more to good food than canned goods and smoothies.  While not juicing onions and pressing garlic, Bryan likes to run half-marathons, discover interesting cuisines with his wife, and help entrepreneurs develop great food products.

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