Episode 1: The Essence of Japanese Cuisine: Dashi

I am Tatsumi, a Geo-activist and director of the Geo-Live Research Institute.
The first episode of this series is themed around "dashi," which is indispensable to Japanese cuisine. Why did a dashi culture develop in Japan? Come on, let's Geo-live!

Dashi packed with umami

Wakatakenie (simmered bamboo shoots and wakame seaweed) is a quintessential spring dish, where the aroma and texture of the bamboo shoots are enhanced by dashi. The depth of this dashi is said to be created by the synergistic effect of the umami from kombu (kelp) and katsuobushi (dried bonito flakes). What is important here is that "umami" has a scientific meaning that is distinct from the sensory expression of "delicious." Our sense of "taste," one of our five senses, is fundamentally a sense for identifying components that are essential or harmful to a living organism. It has long been known that there are four main tastes perceived primarily by the tongue: "sweet," "bitter," "sour," and "salty." The "receptors" in the taste cells of the tongue detect the components corresponding to each. Regarding umami components, Japanese scientists discovered them in Japanese ingredients such as kombu (glutamic acid: Kikunae Ikeda), katsuobushi (inosinic acid: Shintaro Kodama), and shiitake mushrooms (guanylic acid: Akira Kuninaka), but they were not easily accepted in the West, where these ingredients were less familiar. However, with the proof in the early 21st century that glutamic acid receptors exist within taste cells, "umami" finally became widely recognized as a basic taste.
Of course, soup stock is also essential in Western cuisine. However, there is a decisive difference between those and dashi. That difference is the ingredients used. Dashi often uses a combination of kombu and katsuobushi, whereas in France, for example, one of the main players responsible for the umami of soup is animal meat. Many people think the reason meat-based soups did not spread in Japan is due to the influence of Buddhist culture, which dislikes the taking of life. While that is certainly one factor, the nature of the water actually has a significant influence.

Soft water and hard water

One of the scales for expressing the properties of water is "hardness." Water is classified as shown in Figure 1 based on its hardness, which is the amount of Ca and Mg it contains. Using this scale, it is immediately obvious that Japanese water is overwhelmingly softer than water in Europe. Among them, the water of Kyoto, which can be called the home of Japanese cuisine, is ultra-soft water. On the other hand, while water in the Kanto region is classified as soft water, it has a slightly higher hardness, and Okinawa also tends to have higher hardness. Additionally, "Miyamizu," which supports the Nada-gogo (Kobe City/Nishinomiya City), the number one sake-producing region in Japan, is medium-hard water. Actually, these waters, which are unique to the Japanese archipelago, have fostered unique food cultures in their respective regions, but I will talk about that another time; for now, please remember that Japan is a "land of soft water."

I believe that people on the Japanese archipelago also used to boil and eat animal meat in the past. As can be seen from the shell mounds of Jomon ruins, wild boar and deer meat were important sources of protein for ancient people. They must have eaten the meat obtained from hunting by roasting or boiling it. However, boiled meat dishes must have been far too "gamey." This is because they could not effectively remove the odor components (fatty acids and proteins) in the meat and blood. These odor components combine with the Ca contained in water to form "aku" (scum), so if you skim this off thoroughly, you should be able to remove the gamey smell. However, because there is little Ca in the soft water of the Japanese archipelago, the reaction to form scum does not proceed. On the other hand, in Europe, where the water is hard, exquisite "fond de veau" was born by carefully skimming the scum.
While soft water is not suitable for cooking meat, it has characteristics that more than make up for it. It effectively extracts glutamic acid, the umami component of kombu. It can be said that this is what created the dashi that forms the basis of Japanese cuisine. On the other hand, in hard water, the slimy component (alginic acid) contained in kombu reacts with Ca to form a film on the surface. Therefore, if you use hard water, glutamic acid is not sufficiently extracted.
The owner of a long-established restaurant in Kyoto once said this: "I opened a branch in Akasaka, but no matter what I did, I couldn't make the usual dashi. I thought it was the water, so I brought water from Kyoto, and it worked out well!" As I mentioned earlier, water in the Kanto region is somewhat on the hard side.

Mountains and plains that divide soft water and hard water

A Dutch civil engineer who came to Japan during the Meiji era wrote this: "There are no rivers in this country. What there are, are waterfalls." This should be clear if you look at Figure 2. Compared to the continent, the riverbeds of the Japanese archipelago have an overwhelmingly large gradient and are rapid streams. Actually, this is the very reason why Japan became a "land of soft water."

In continental rivers that flow slowly over time, a large amount of Ca and Mg ions contained in the ground dissolve, resulting in hard water. Furthermore, because calcareous ground, which has these elements as its main components, spreads across Europe, the hardness of the water increases even more. On the other hand, because the rivers of the Japanese archipelago are overwhelmingly rapid, there is no time for ions to dissolve, resulting in soft water.
The same can be said for groundwater. The average time that groundwater remains underground (residence time) is said to be over 10,000 years on the continent, for example in Central Europe or Texas in the United States, whereas it is less than a few decades for mountain springs in Japan, and about 5 years even in the Kyoto Basin.
In the Kanto region, where Japan's largest plains spread out amidst the Japanese archipelago with its many rapid streams, the Tone River and Arakawa River flow slowly. For that reason, it is thought that the hardness of the water is higher compared to other regions, making it somewhat more difficult to make kombu dashi. Also, Okinawa, where the ground is made of limestone originating from coral reefs, is also a hard water system. In addition, "Miyamizu," which is used for sake brewing in Nada (Kobe City to Nishinomiya City, Hyogo Prefecture), the number one sake-producing region in Japan, is medium-hard water. The reason for this is that this water flows through strata containing many shells, which have Ca as their main component.
The fact that Japan is a land of soft water, and as a result, a culture of making dashi with kombu was fostered, was because there are many rapid streams—in other words, because this country is a mountainous island nation. So why do the mountains in this country become so high? Let's talk about that next time.