"Now it is evident, that in this prophecy[allusion is made] to the bread which our Christ gave us to eat, in remembrance of His being made flesh for the sake of His believers, for whom also He suffered; and to the cup which He gave us to drink, in remembrance of His own blood, with giving of thanks.”
chapter 70
Justin explicitly stated that bread (not the flesh) is given by Christ in remembrance of His flesh, and that the cup is in remembrance of – not is – His own blood. If Justin believed in transubstantiation i.e. the real presence, he would have certainly stated it here, instead he refutes it.