Why does broth taste savory even with no salt added?
That deep savory hit in a good broth is not salt - it is a taste all its own.
Umami is the fifth basic taste, alongside sweet, sour, salty, and bitter. Your tongue has a dedicated receptor (built from proteins T1R1 and T1R3) that detects free glutamate, the savory molecule in kombu, aged cheese, ripe tomatoes, and meat. It is not saltiness and not just MSG - it is a real signal the brain reads on its own.
A bowl of pho with no extra salt still tastes deeply savory - the simmered bones and fish sauce flood it with glutamate, and your umami receptor lights up.
Savory depth is a separate taste from salty - you can boost flavor with glutamate-rich foods, not just more salt.
Knowing umami is its own taste lets you make food taste richer using tomatoes, mushrooms, or fish sauce instead of piling on salt.
Umami = the fifth taste - the savory one your tongue catches with its own glutamate sensor.
Learn the idea and practice English at the same time.