Trying to get a grasp of how to use the word 豊富な, I found a phrase saying 「タンパク質が豊富な」 from a Japanese website. I’m not sure if が must be used for it to be correctly mean “protein-rich” or “rich in protein” And then there’s my own phrase: 「豊富なタンパク質」. If I mean “abundant protein”, is this correct?
EDIT: The full sentence is "タンパク質が豊富な食材13選"
豊富 is a rather simple na-adjective meaning abundant, and you can say both 豊富なタンパク質 and タンパク質が豊富な食材, just as you can say the following:
Grammatically, these ～が～な form relative clauses that modify a noun.
I don't know where you found the phrase, but if you know about "conjugated part ending" of Japanese, you also know that "な" of the word of "豊富な" is used when the word is before some noun. It's called "attributive form." If you can't find noun after the word "豊富な," it must be omitted. You can infer what the noun is by reading context.
So the answers: Both expressions you proposed can be correct and “abundant protein” is also able to be translated into "豊富なタンパク質."
And you've questioned about "が," haven't you? "が" is one of Japanese postpositions, "joshi," that means the noun before itself is subject, and also you can use it to supplement noun with verb, like "relative pronoun." So precisely, "タンパク質が豊富な食材" is "ingredients which is protein-rich" or "ingredients which is rich in protein." This is the closest expression for this Japanese phrase, I think.
