Salty, sweet, sour, bitter. Scientists once thought these were the only tastes, but in the early 20th century, a Japanese chemist dissected his favorite kombu broth and discovered one more: umami. In recent years, umami has become a foodie buzzword, but for nearly a century, the Western world was in full-blown umami denial—didn’t believe it existed. And we might have stayed that way if it weren’t for our most notorious and potent source of umami: MSG.   A 1930s advertisement for Ajinomoto. (Courtesy of the Science History Institute.)   Advertising brochure from the late 1940s until the early 1950s for Ac'cent, an MSG product manufactured by the International Minerals & Chemical Corporation. (Courtesy of the Science History Institute.)   Kikunae Ikeda, who proposed the idea of umami as a fifth basic taste. (Wikimedia Commons)   Guest:  Nirupa Chaudhari is a professor of physiology & biophysics at the University of Miami. Kumiko Ninomiya is the director of the Umami Information Center.  Footnotes & Further Reading:  Special thanks to Sarah Tracy for some background on MSG in the United States. Read a translation of Kikunae Ikeda's original manuscript in Journal of the Chemical Society of Tokyo. "A Short History Of MSG" discusses Ajinomoto's marketing techniques, as well as reception of MSG in the United States and around the globe.  If you're dying to see the Mr. Umami video mentioned in this story, watch it here. Hear more chefs gushing over umami at the Austin Food & Wine Festival.  Credits:  Science Diction is hosted and produced by  Johanna Mayer. Elah Feder is our editor and producer. Nathan Tobey contributed story editing, and Kaitlyn Schwalje contributed writing and research. Thanks also to Lauren J. Young and Attabey Rodríguez Benítez for research help. Our composer is Daniel Peterschmidt, and they also did sound design. Chris Wood mastered this episode. We had fact checking from Michelle Harris. Nadja Oertelt is our Chief Content Officer.