In another passage, Clement contradicts transubstantiation. He writes the following about how Christians should conduct themselves when drinking alcohol (emphasis added):
In what manner do you think the Lord drank when He became man for our sakes? As shamelessly as we? Was it not with decorum and propriety? Was it not deliberately? For rest assured, He Himself also partook of wine; for He, too, was man. And He blessed the wine, saying, “Take, drink: this is my blood”–the blood of the vine. He figuratively calls the Word “shed for many, for the remission of sins”–the holy stream of gladness. And that he who drinks ought to observe moderation, He clearly showed by what He taught at feasts. For He did not teach affected by wine. And that it was wine which was the thing blessed, He showed again, when He said to His disciples, “I will not drink of the fruit of this vine, till I drink it with you in the kingdom of my Father.” [Matthew 26:29] But that it was wine which was drunk by the Lord, He tells us again, when He spake concerning Himself, reproaching the Jews for their hardness of heart: “For the Son of man,” He says, “came, and they say, Behold a glutton and a wine-bibber, a friend of publicans.” (The Instructor, 2:2)
Clement, like evangelicals, cites Matthew 26:29 as evidence that Jesus drank wine. If Clement believed that wine is what was drunk at the Last Supper, he didn’t believe in transubstantiation.
Similarly, Irenaeus denies transubstantiation in his writings. He seems to have believed in consubstantiation rather than the Catholic view of the eucharist. For example (emphasis added):
For as the bread, which is produced from the earth, when it receives the invocation of God, is no longer common bread, but the Eucharist, consisting of two realities, earthly and heavenly; so also our bodies, when they receive the Eucharist, are no longer corruptible, having the hope of the resurrection to eternity. (Against Heresies, 4:18:5)
For this reason, when about to undergo His sufferings, that He might declare to Abraham and those with him the glad tidings of the inheritance being thrown open, Christ, after He had given thanks while holding the cup, and had drunk of it, and given it to the disciples, said to them: “Drink ye all of it: this is My blood of the new covenant, which shall be shed for many for the remission of sins. But I say unto you, I will not drink henceforth of the fruit of this vine, until that day when I will drink it new with you in my Father’s kingdom.” Thus, then, He will Himself renew the inheritance of the earth, and will re-organize the mystery of the glory of His sons; as David says, “He who hath renewed the face of the earth.” He promised to drink of the fruit of the vine with His disciples, thus indicating both these points: the inheritance of the earth in which the new fruit of the vine is drunk, and the resurrection of His disciples in the flesh. For the new flesh which rises again is the same which also received the new cup. And He cannot by any means be understood as drinking of the fruit of the vine when settled down with his disciples above in a super-celestial place; nor, again, are they who drink it devoid of flesh, for to drink of that which flows from the vine pertains to flesh, and not spirit. (Against Heresies, 5:33:1)
Irenaeus describes the eucharist as consisting of two realities, one that comes from Heaven and another that’s from the earth. He refers to the eucharist as an example of drinking wine, the same substance that people will drink in Christ’s future kingdom, after the eucharist has served its purpose (1 Corinthians 11:26). Irenaeus, like Clement of Alexandria, contradicts transubstantiation. Though Irenaeus does seem to have believed in a presence in the eucharist, it isn’t transubstantiation.
Other examples could be cited, and other examples are cited in the article I linked to above. It’s a historical fact that the church fathers held a variety of eucharistic beliefs, including some that contradict what the Catholic Church teaches. This fact is contrary to the Council of Trent’s claim that transubstantiation had always been the view held by the Christian church.