I call BS on Umami.
All this talk about Umami being this 5th flavor is bull. To me, Umami simply means 'good flavor', and its just a word. Whenever I hear someone use the word Umami to describe a depth of 'taste' in a food, my Japanese spidey senses tingle.
Here is why.
Its yet another example of slight semantic shifting.
The extent in which dashi is used in Japanese cuisine is no secret to the Japanese. It exists in almost everything in Japanese food. It gives everything a bolder, deeper, richer flavor. An example is the difference in taste of American Mayonnaise and Japanese Mayonnaise. Japanese Kewpie Mayonnaise has dashi in it as part of its 'not-so-secret' ingredient, the rest of the basic ingredients are the same but they are very distinctly different. So I believe the attempt to define this distinct essense or flavor lead people to coin and spread the use of 'Umami'. The Japanese word for 'good flavor' is now intentionally being marketed as this distinct essence.
It also turns out that the maker of this manufactured essence more commonly known as MSG is Ajinomoto. Their site reveals that one of its goals is to 'educate the world about umami'.
"In addition to spreading understanding of the umami seasoning AJI-NO-MOTO®, the Ajinomoto Group is helping to communicate the fact that umami is a universal taste, common to food cultures the world over"
So in conclusion, I believe the spread of the word Umami outside of Japan to describe the richness in taste of dashi stock is a result of strategic corporate marketing.