The following answer is from the Catholic Encyclopedia “Sacrifice of the Mass”:
“While the Consecration as such can be shown with certainty to be the act of Sacrifice, the necessity of the twofold consecration can be demonstrated only as highly probable. Not only older theologlans such as Frassen, Gotti, and Bonacina, but also later theologians such as Schouppen, Stentrup and Fr. Schmid, have supported the untenable theory that when one of the consecrated elements is invalid, such as barley bread or cider, the consecration of the valid element not only produces the Sacrament, but also the (mutilated) sacrifice. Their chief argument is that the sacrament in the Eucharist is inseparable in idea from the sacrifice. But they entirely overlooked the fact that Christ positively prescribed the twofold conscration for the sacrifice of the Mass (not for the sacrament), and especially the fact that in the consecration of one element only the intrinsically essential relation of the Mass to the sacrifice of the Cross is not symbolically represented. Since it was no mere death from suffocation that Christ suffered, but a bloody death, in which His veins were emptied of their Blood, this condition of separation must receive visible representation on the altar, as in a sublime drama. This condition is fulfilled only by the double consecration, which brings before our eyes the Body and the Blood in the state of separation, and thus represents the mystical shedding of blood. Consequently, the double consecration is an absolutely essential element of the Mass as a relative sacrifice.”
It still doesn’t fully answer the question, “What if the bread is consecrated but vinegar wrongly placed in the cup (which cannot be truly consecrated) is not consecrated? What comes of the bread? Do you have a sacrament without sacrifice?