Excerpti: The Eucharist, Part II: What is the matter of the Eucharist?

This is the second installment of Excerpti (extracts); the series is currently focused on the Eucharist, the Most Blessed Sacrament. This is Part II: What is the matter of the Eucharist? (Not "What is the matter with the Eucharist?")

Summary
Regardless of leaven in the bread (see below), the bread must contain wheat gluten; the wine must contain alcohol. Low-gluten bread and mustum are allowed under specific circumstances. (cf. Norms for the Use of Low-Gluten Bread and Mustum; The Use of Mustum and Low-Gluten Hosts at Mass)

In the Western tradition:

• Unleavened wheat bread. (Cf. CIC, can. 924 §§1, 2)
• Natural grape wine mixed with water. (Cf. CIC, can. 924 §§1, 3)

In the Eastern tradition:

• Leavened wheat bread (except in the Armenian and Maronite rites, where it is unleavened). (Cf. CCEO, can. 706)
• Natural grape wine mixed with water. (Cf. CCEO, can. 706)

The wine is mixed with water during the Offertory in the Western rites; the wine is mixed with the water during the Proskomedia in the Eastern rites.

Western Canon Law
"The most holy Sacrifice of the Eucharist must be celebrated in bread, and in wine to which a small quantity of water is to be added." (CIC, can. 924 §1)

"The bread must be wheaten only, and recently made, so that there is no danger of corruption." (CIC, can. 924 §2)

"The wine must be natural, made from grapes of the vine, and not corrupt." (CIC, can. 924 §3)

Eastern Canon Law
"In the Divine Liturgy the sacred gifts which are offered are bread made of wheat alone and recently made so that there is no danger of corruption and natural wine of the grape and not corrupt." (CCEO, can. 706)

Other Documents
"The bread for Eucharistic celebration is bread of wheat and, in keeping with the age-old custom of the Latin Church, unleavened." (Sacred Congregation for Divine Worship, 1970 - Liturgicae Instaurationes, n. 5)

"Faithful to Christ's example, the Church has constantly used bread and wine mixed with water to celebrate the Lord's Supper. The bread for the celebration of the Eucharist, in accordance with the tradition of the whole Church, must be made solely of wheat, and, in accordance with the tradition proper to the Latin Church, it must be unleavened. By reason of the sign, the matter of the Eucharistic celebration 'should appear as actual food.' This is to be understood as linked to the consistency of the bread, and not to its form, which remains the traditional one. No other ingredients are to be added to the wheaten flour and water. The preparation of the bread requires attentive care to ensure that the product does not detract from the dignity due to the Eucharistic bread, can be broken in a dignified way, does not give rise to excessive fragments, and does not offend the sensibilities of the faithful when they eat it. The wine for the Eucharistic celebration must be of 'the fruit of the vine' (Lk. 22:18) and be natural and genuine, that is to say not mixed with other substances. {Cf. Liturgicae Instaurationes, n. 5}" (Sacred Congregation for the Sacraments and Divine Worship, 1980 - Inaestimabile Donum, n. 8)

"Special hosts quibus glutinum ablatum est" -- that is, "whose gluten is removed" -- "are invalid matter for the celebration of the eucharist." (Congregation for the Doctrine of the Faith, 1994 - Norms for the Use of Low-Gluten Bread and Mustum, I.B.1)

"Low-gluten hosts are valid matter, provided that they contain the amount of gluten sufficient to obtain the confection of bread, that there is no addition of foreign materials and that the procedure for making such hosts is not such as to alter the nature of the substance of the bread." (Congregation for the Doctrine of the Faith, 1994 - Norms for the Use of Low-Gluten Bread and Mustum, I.B.2)

"Nevertheless, the permission to use mustum can be granted by ordinaries to priests affected by alcoholism or other conditions which prevent the ingestion of even the smallest quantity of alcohol, after presentation of a medical certificate." (Congregation for the Doctrine of the Faith, 1994 - Norms for the Use of Low-Gluten Bread and Mustum, II.B)

"By mustum is understood fresh juice from grapes or juice preserved by suspending its fermentation (by means of freezing or other methods which do not alter its nature)." (Congregation for the Doctrine of the Faith, 1994 - Norms for the Use of Low-Gluten Bread and Mustum, II.C)

"Following the example of Christ, the Church has always used bread and wine with water to celebrate the Lord’s Supper." (GIRM, n. 319)

"The bread for celebrating the Eucharist must be made only from wheat, must be recently baked, and, according to the ancient tradition of the Latin Church, must be unleavened." (GIRM, n. 320)

"The wine for the eucharistic celebration must be from the fruit of the grapevine (cf. Lk 22:18), natural, and unadulterated, that is, without admixture of extraneous substances." (GIRM, n. 322)

"Diligent care should be taken to ensure that the bread and wine intended for the Eucharist are kept in a perfect state of conservation: that is, that the wine does not turn to vinegar nor the bread spoil or become too hard to be broken easily." (GIRM, n. 323)

"Hosts that are completely gluten-free are invalid matter for the celebration of the Eucharist." (Congregation for the Doctrine of the Faith, 2003 - Prot. 89/78-174 98, A.1)

"Low-gluten hosts (partially gluten-free) are valid matter, provided they contain a sufficient amount of gluten to obtain the confection of bread without the addition of foreign materials and without the use of procedures that would alter the nature of bread." (Congregation for the Doctrine of the Faith, 2003 - Prot. 89/78-174 98, A.2)

"Mustum, which is grape juice that is either fresh or preserved by methods that suspend its fermentation without altering its nature (for example, freezing), is valid matter for the celebration of the Eucharist." (Congregation for the Doctrine of the Faith, 2003 - Prot. 89/78-174 98, A.3)

"The Ordinary is competent to give permission for an individual priest or layperson to use low-gluten hosts or mustum for the celebration of the Eucharist. Permission can be granted habitually, for as long as the situation continues which occasioned the granting of permission." (Congregation for the Doctrine of the Faith, 2003 - Prot. 89/78-174 98, C.1)

"The bread used in the celebration of the Most Holy Eucharistic Sacrifice must be unleavened, purely of wheat, and recently made so that there is no danger of decomposition. {Cf. CIC, can. 924 §2; GIRM, n. 320} It follows therefore that bread made from another substance, even if it is grain, or if it is mixed with another substance different from wheat to such an extent that it would not commonly be considered wheat bread, does not constitute valid matter for confecting the Sacrifice and the Eucharistic Sacrament. It is a grave abuse to introduce other substances, such as fruit or sugar or honey, into the bread for confecting the Eucharist. Hosts should obviously be made by those who are not only distinguished by their integrity, but also skilled in making them and furnished with suitable tools." (Congregation for Divine Worship and the Discipline of the Sacraments, 2004 - Redemptionis Sacramentum, n. 48)

"The wine that is used in the most sacred celebration of the Eucharistic Sacrifice must be natural, from the fruit of the grape, pure and incorrupt, not mixed with other substances. {Cf. CIC, can. 924 §§1, 3; GIRM, n. 322} During the celebration itself, a small quantity of water is to be mixed with it. Great care should be taken so that the wine intended for the celebration of the Eucharist is well conserved and has not soured. {Cf. GIRM, n. 323} It is altogether forbidden to use wine of doubtful authenticity or provenance, for the Church requires certainty regarding the conditions necessary for the validity of the sacraments. Nor are other drinks of any kind to be admitted for any reason, as they do not constitute valid matter." (Congregation for Divine Worship and the Discipline of the Sacraments, 2004 - Redemptionis Sacramentum, n. 50)