ripening vs mellowing

ripening and mellowing both are nouns.

Word	Noun	Adjective	Verb	Adverb
ripening	Yes	No	No	No
mellowing	Yes	No	No	No

As nouns, mellowing is a hyponym of ripening; that is, mellowing is a word with a more specific, narrower meaning than ripening:

ripening: acquiring desirable qualities by being left undisturbed for some time
mellowing: the process of becoming mellow

ripening (noun)	mellowing (noun)
coming to full development; becoming mature	the process of becoming mellow
acquiring desirable qualities by being left undisturbed for some time