Transubstantiation is the doctrine that it ceases being bread and wine. Which St Paul kind of debunks in his first letter to the Corinthians at Chapter 11, where he refers to it as bread.

“For as often as you eat this bread and drink the cup, you proclaim the Lord’s death until he comes.”

What you’re talking about is consubstantiation, which is where the body and blood physically coexist in the bread and wine, which can be derived from the Bible.