What we call the Old Testament was already in existence, Luke 24:44.
The Catholic Church determined both Old Testament and New.
When Jesus taught about Himself being the true Manna from Heaven He had not yet instituted His Remembrance. John 6:35-63. And that was not written until about 95 or so AD. And to claim it was about the Remembrance is contrary to its contexts.
Jesus flesh is real food and blood is real drink. Not only is it the words of Scripture, it’s Jesus own Words.
This is the Manna we receive down the ages each day the living journeying Church, we receive and are sustained by Jesus Himself in Eucharistic Covenant.