Today the Eucharist is seen more in a personalistic way; it is an encounter between Jesus Christ and the individual in the Church, hence we do not hear much about the objective factors of the sacrament namely the matter and form of the Eucharist. This does not mean that the Church is any more insisting on the sacramental nature of the Eucharist. Cf. Canons 924-930;
a) MATTER: The first element is wheaten bread cf. ND 1509 and 1508. Many theologians consider that the use of wheaten bread is for the validity of the sacrament. Why wheaten bread? We can say that it is according to the ancient custom of the Church. Use of unleavened bread or leavened bread (among Eastern Churches) is permitted according to the custom (cf. Christian Faith 1508). Read: Tour of Summa p.378 ff. Instruction, Redemptionis Sacramentum, 2004, nos. 48;49 and 50 deal with the matter of the Eucharist. CCC, 1333.
The second element is natural grape wine. Christ himself used it at the Last Supper (cf.Mk 14:25; Mt. 26:29). A little amount of water was added to the wine. This mixing of water is in existence from the early Church cf. FEF 128. This is explained in a symbolic way as the flowing of water from the wound of Christ’s side.
b) FORM: The words of Institution uttered by Christ are the form of this sacrament. For the Greek-Orthodox Church it is the “epiclesis” alone or the words of institution along with epiclesis are the form of the sacrament. The Catholic Church teaches…cf. Christian Faith 1510; See also: Tour of Summa p.384; CCC 1333.
The words of Institution demonstrates, at least with high degree of probability, that at the Last Supper Jesus effected the change (transmutation) by the words: “this is my body”, “this is my blood”, and not by an act of the will or blessing or thanksgiving. How this is possible? How is that such a few words are so powerful to make revolutionary change in the elements? Is it not a magic? To understand this we must see the power of God’s word. The word of God is absolutely marvelous, mysterious and the manifests the salvific plan of God. It is the Word of God that makes this sacrament possible. “Fathers regarding this divine sacrament: “Do not see – Saint Cyril of Jerusalem exhorts – in the bread and wine merely natural elements, because the Lord has expressly said that they are his body and his blood: faith assures you of this, though your senses suggest otherwise” (as quoted in EE 15)
There is another question: Does the priest consecrate solely by virtue of the words of institution, or also by means of the so called Epiclesis, which occurs in the Oriental Liturgies shortly after the words of Institution and expresses a petition to the Holy Spirit, “that the bread and wine be converted into the body and blood of Christ.” The COT says immediately after consecration the elements become body and blood of Christ cf. Christian Faith 1513. Consequently the Latin tradition held that the epiclesis has no consecratory function, but only a declarative significance. Today in the COCC we read “At the heart of the Eucharistic celebration are the bread and wine that, by the words of Christ and the invocation of the Holy Spirit, become Christ’s Body and Blood” (1333).
The Change of the elements of bread and wine is possible only through the consecratory words. This was asserted by the Church when she rejected the 9th century idea that by mixing a non-consecrated element with the consecrated element, the non- consecrated becomes consecrated. The false idea was based on the assumption that a sacred thing assimilates a non-sacred thing to itself. This was rejected by St. Thomas Aquinas, cf. Tour of Summa p. 379 and subsequent Councils too speak about the necessity of Consecratory words Christian Faith 1510. We have also the testimony of the Fathers of the Church. Tertullian cf. FEF 342; Justin the Martyr FEF 128; St. Ambrose Cf. Messages of the Fathers of the Church, no.7, p.80.; Origen cf. Messages of the Fathers of the Church, no.7, p.188 para.2.