mellowness vs taste sensation

mellowness and taste sensation both are nouns.

Word	Noun	Adjective	Verb	Adverb
mellowness	Yes	No	No	No
taste sensation	Yes	No	No	No

As nouns, taste sensation is a hypernym of mellowness; that is, taste sensation is a word with a broader meaning than mellowness:

mellowness: a taste (especially of fruit) that is ripe and of full flavor
taste sensation: the sensation that results when taste buds in the tongue and throat convey information about the chemical composition of a soluble stimulus

Other hypernyms of mellowness include gustatory perception, gustatory sensation, taste, taste perception.

mellowness (noun)	taste sensation (noun)
the property of a sensation that is rich and pleasing	the sensation that results when taste buds in the tongue and throat convey information about the chemical composition of a soluble stimulus
a soft shade of a color
geniality, as through the effects of alcohol or marijuana
a taste (especially of fruit) that is ripe and of full flavor
a feeling of good humor and sympathy through maturity or intoxication or a relaxed state