The theory of the four tastes, also named four basic tastes is wrong: any person able to document a little will discover easily that the specialists know very well the fallacy of this theory.
Those who know the error unfortunately fall into the idea that there is a fifth taste, which was named "umami". However, I must disabuse them: we must fight against this idea, which has been widely accredited by sellers of monosodium glutamate.
Invited to visit one of the largest manufacturers of "dashi" in Tokyo, I witnessed the making of this stock: kombu seaweed are washed down with hot water, so that two amino acids were extracted (alanine and glutamic acid). I was told that the flavor of this broth, or stock, was umami.
OK, why not. But in this cas, the umami taste is not "elementary", since it is the mixture of the taste of alanine and of the taste of glutamic acid.
As a corollary, we must admit that the taste of monosodium glutamate, which is not glutamic acid, is not umami, as it is not the mixed taste of alanine and glutamic acid.
In total, I don't see how umami could existe.
In contrast, amino acids have all different flavors. This is good news for cooks, which adds new piano keys.
And finally, some questions for those who would think that there would be only 5 tastes, instead of 4 : did you taste sodium bicarbonate ? and ethanol ? and liquorice ? How do they taste ;-) ?