While taste physiologists have traditionally pointed to four basic flavours - sweet, salty, sour and bitter - Japanese culture has long held the notion of a fifth flavour, umami. Today, umami is rapidly gaining acceptance in Western culture, thanks in no small part to the increasing popularity of Asian cuisine.
So what exactly is umami? Often translated as "savoury" or "brothy," umami can be described as the tongue-coating, meaty flavour of sauteed mushrooms, a juicy steak, aged cheese, or a rich stock. Physiologically, the umami taste is related to the presence of glutamic acid, which is abundant in protein-rich foods. Recent theories have suggested that the experience of umami is a result of glutamic acid working synergistically with olfactory sensors and salt. The result is a rich, fully rounded flavour that's well-enhanced. Not surprisingly, soy sauce has plenty of the elements that make up the elusive umami. Adding naturally brewed soy sauce to a variety of food products can add the allure of umami's richness and fully-rounded flavor without adding MSG.
Umami is particularly desirable in processed foods, where rapid preparation can be an obstacle; the cooking time required to develop rich, meaty flavours is often overridden by tight production schedules. By adding a little soy sauce to the formula, the amino acid content can help fill in the blanks in the flavour profile without having to add hydrolyzed vegetable protein.