I still think "umami" looks out of place next to the other basic taste words. All the others come in adjective/noun pairs: sweet/sweetness, salty/saltiness, etc. Where's the adjective for "umami"? "Umami" again? "Umami-tasting"? It doesn't work well (and importing the Japanese adjective "umai" would make things worse, not better).

Instead, I highly prefer the adjective sapid with its corresponding noun sapidity. Sweet, sour, salty, bitter, sapid. Sweetness, sourness, saltiness, bitterness, sapidity. Much better.