At what point during the Mass are the bread and wine changed into the body and blood of Christ?
June 21, 2020, 12:00 PM
During the Eucharistic Prayer, the priest prays the words of consecration. At this point, the bread and wine are “transubstantiated” and become the sacred body and blood of Jesus. This is when the priest solemnly pronounces the words of Christ: “This is my body” and “This is my blood,” elevating the host and the chalice immediately afterward. Notice that the priest doesn’t say “This is the body of Jesus,” but rather, “This is my body.” This is because the priest, during the Mass, is acting in persona Christi (“in the person of Christ”); he literally is standing in for Jesus when celebrating the Eucharist. (See CCC 1377 and 1413 for more on this topic.)
BONUS QUESTION: After the bread and wine at Mass are changed into the body and blood of Christ, would a DNA test on them show human flesh and blood?
No. At the Last Supper when Jesus said, “This is my body,” the host that He held in His hands continued to have physical properties of bread: it looked, felt, and tasted like unleavened bread. Yet the apostles took Jesus at His word. It was no longer bread, it was Jesus himself, and this miraculous change has occurred at every valid Mass since then. So, if the bread does not change in appearance, then how does it change? It changes in substance. Thus, we call this change transubstantiation.
In philosophical language, substance refers to the “whatness” of something. A grain of wheat changes in size, shape, and color as it sprouts and grows, but it remains an individual plant of its species: its properties (the “appearances”) change, while its substance (“what it is”) stays the same.
Miraculously, the opposite occurs in the consecration of the Eucharist. Even though the physical properties of bread and wine are still there, the underlying substance “bread” changes into the substance “body and blood of Christ.” After the consecration, the host is no longer a piece of bread; it is Jesus. It is not Jesus present somehow “in” bread; it is Jesus really present under the appearance (i.e., form) of bread. It is 100 percent Jesus - His body, blood, soul, and divinity.