Adversus Haereses (Against the Heresies) St. Irenaeus circa 180 A.D.
St. Irenaeus was born somewhere between 115 and 125 AD. He was a disciple of St. Polycarp, St. Polycarp was a disciple of St. John, author of the 4th Gospel and disciple of Christ. So we have in Irenaeus teachings of the faith which are only one generation removed from the Apostles themselves. He became the Bishop of Lyon and is one of the Church Fathers.
St. Irenaeus writing a famous tract Against Heresies between 180 and 190 A.D. is the first to provide explicit mention of the change that takes place in the bread and wine when they become the Eucharist:
"The earthly creation (bread and wine) are raised to a heavenly dignity after they "receive the word of God" [at the epiclesis of the Mass or the invocation to the Holy Spirit] and become the food and drink of Christians. So how then can we doubt that, "Our bodies, receiving the Eucharist, are no longer corruptible but have the hope of resurrection to eternal life."
"If the body be not saved, then in fact, neither did the Lord redeem us with His Blood; and neither is the cup of the Eucharist the partaking of His Blood nor is the Bread which we break the partaking of His Body . . . He has declared the cup, a part of creation, to be His own Blood, from which He causes our blood to flow; and the bread, a part of creation, He has established as His own Body, from which He gives increase to our bodies. "
Again, giving counsel to His disciples to offer to God the first-fruits from among His creatures, not as if He needed them, but so that they themselves might be neither unfruitful nor ungrateful, He took from among creation that which is bread, and gave thanks, saying, ``This is My Body.'' The cup likewise, which is from among the creation to which we belong, He confessed to be His Blood.He taught the the new sacrifice of the New Covenant, of which Malachi, one of the twelve prophets, had signified beforehand: ```You do not do my will,' says the Lord Almighty, `and I will not accept a sacrifice at your hands. For from the rising of the sun to its setting My name is glorified among the gentiles, and in every place incense is offer to My name, and a pure sacrifice; for great is My name among the gentiles,' says the Lord Almighty.'' (Mal 1:11). By these words He makes it plain that the former people will cease to make offerings to God; but that in every place sacrifice will be offered to Him, and indeed, a pure one; for His name is glorified among the gentiles"
If you are a Christian and you have never read the Early Church Fathers who were eye witnesses to the Church, what its beliefs were and how those beliefs came about from the Apostles themselves, do yourself a favor. The Catholic Church did not contrive these beliefs, many centuries later as some would want you to believe.