No, the kokumi sensation is not a Japanese pop group, which would have been my guess. You've heard of umami, right? It's the fifth basic taste, in addition to salty, sweet, sour and bitter. Translated from Japanese as "savory" or "yummy," umami has only relatively recently been recognized in the West.
Well, kokumi is another food attribute identified by the Japanese. It is sometimes translated as "heartiness" or "mouthfulness" and describes compounds in food that don't have their own flavor, but enhance the flavors with which they're combined. These compounds include calcium, protamine (found in milt, or fish sperm, which is eaten in Japan and Russia), L-histidine (an amino acid) and glutathione (found in yeast extract).
Food scientists have been studying kokumi compounds in hopes of exploiting their enhancement qualities to create healthier, lower-salt or -sugar versions of foods that still taste good. But first they have to figure out how the mechanism works—
I bet you didn't know you had calcium channels on your tongue—and, until 2008, neither did scientists. According to the journal's press release, "these channels sense and regulate the levels of calcium in the body ... noted that calcium channels are closely related to the receptors that sense sweet and umami (savory) tastes and that glutathione (a common kokumi taste element) is known to interact with calcium channels."
The researchers conducted taste tests on a panel of volunteers trained to distinguish flavors, and found that the compounds—including glutathione and calcium—that activated the strongest response in calcium receptors also produced the most flavor enhancement.
So does this mean adding a calcium supplement to diet foods will make them more palatable (while giving you a boost in your levels of the necessary mineral)? It's not that simple. The 2008 study that discovered the calcium receptors on the tongue also noted that many people appear to experience calcium as an unpleasant taste, except in foods like milk and cheese, where it binds with fat. As Paula Deen would attest, fat (especially butter) is the ultimate flavor enhancer—but not exactly diet food.