Final answer:
Umami receptors respond most strongly to the taste of savory foods, which are often protein-rich.
Step-by-step explanation:
The umami taste is most strongly responded to by umami receptors. Umami is the taste associated with savoriness and is attributed to the amino acid L-glutamate. Umami receptors are activated by the presence of L-glutamate, which is commonly found in protein-rich foods. Therefore, umami helps in identifying foods that contain essential amino acids.