Umami, often called the “fifth taste,” is a distinct savory sensation that complements sweet, sour, salty, and bitter. It represents a pleasant, brothy quality found in various foods. Our ability to perceive this unique taste relies on specialized taste receptors on the tongue. These receptors detect umami compounds, allowing our brain to recognize this savory flavor.
The Nature of Umami
The taste of umami was first scientifically identified in 1908 by Japanese chemist Kikunae Ikeda, who discovered that the savory taste in kombu dashi, a Japanese broth made from kelp, was due to glutamate, an amino acid. Umami is characterized by a savory, brothy, and often mouth-filling sensation, distinct from other basic tastes.
Beyond glutamate (found in foods like tomatoes, aged cheeses, and mushrooms), ribonucleotides like inosinate (in dried bonito flakes) and guanylate (in shiitake mushrooms) also elicit umami. These ribonucleotides do not produce umami on their own but significantly amplify the umami taste when combined with glutamate, a phenomenon known as umami synergy. This synergistic effect can increase the perceived umami intensity by as much as 15-fold, explaining why certain food pairings are particularly delicious.
How Umami Receptors Function
The perception of umami on the tongue is mediated by specific proteins, the T1R1 and T1R3 receptor subunits, which form a heterodimer (T1R1/T1R3). These G protein-coupled receptors (GPCRs) are located on the surface of taste receptor cells within taste buds. When umami compounds, such as L-glutamate, bind to the T1R1/T1R3 receptor, the receptor undergoes a change in its shape.
This change activates associated G proteins, specifically Gustducin, initiating a signaling cascade within the taste receptor cell. This cascade involves the release of secondary messengers that modulate ion channel activity. The modulation of ion channels leads to the depolarization of the taste receptor cell, generating an action potential. This electrical signal is then transmitted to the brain, where it is interpreted as the umami taste.
Umami Receptors Beyond the Tongue
Umami receptors, including the T1R1/T1R3 heterodimer, are found not only on the tongue but also in the gastrointestinal (GI) tract, specifically in cells lining the stomach and intestines. Their presence suggests a broader physiological role beyond simply perceiving taste in the mouth.
These gut-based umami receptors sense nutrient availability in the digestive system. When glutamate is detected in the stomach, it can stimulate nerve fibers, leading to increased acid and pepsinogen release. In the duodenum, glutamate can increase mucus production, which helps protect the mucosa from gastric acid. These actions highlight their involvement in regulating digestion and potentially influencing appetite and satiety signals.
The Importance of Umami Perception
Umami plays a significant role in human diet and health, extending beyond taste enjoyment. The savory quality of umami-rich foods can stimulate appetite and enhance the palatability of dishes, promoting better digestion and nutrient absorption. This is beneficial for populations like the elderly, who may experience reduced taste sensitivity and appetite.
Incorporating umami into meals can help reduce the need for excessive salt and fat while maintaining flavor, contributing to healthier eating habits. Chefs worldwide utilize umami-rich ingredients like aged cheeses, mushrooms, and fermented foods to deepen flavors and create satisfying culinary experiences. The ability to detect umami flavors is important for maintaining a healthy daily life, influencing food choices and nutritional intake.