In Roman Catholic liturgy, mustum is grape juice that is only minimally fermented, for use in place of sacramental wine. It is precisely defined as "grape juice that is either fresh or preserved by methods that suspend its fermentation without altering its nature (for example, freezing)," and it excludes pasteurized grape juice.
The Church has declared mustum to be valid matter for the celebration of the Eucharist.
This teaching goes back at least to the time of Pope Julius I (337-352), who is quoted in Thomas Aquinas's Summa Theologica as having declared that in case of necessity, but only then, juice pressed from a grape could be used.
Aquinas himself declared:
- Must has already the species of wine, for its sweetness ["Aut dulcis musti Vulcano decoquit humorem"; Virgil, Georg. i, 295] indicates fermentation which is "the result of its natural heat" (Meteor. iv); consequently this sacrament can be made from must. ... It is forbidden to offer must in the chalice, as soon as it has been squeezed from the grape, since this is unbecoming owing to the impurity of the must. But in case of necessity it may be done: for it is said by the same Pope Julius, in the passage quoted in the argument: "If necessary, let the grape be pressed into the chalice."
- The Ordinary is competent to give permission for an individual priest or layperson to use 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.
- When the principal celebrant at a concelebration has permission to use mustum, a chalice of normal wine is to be prepared for the concelebrants.
- Given the centrality of the celebration of the Eucharist in the life of a priest, one must proceed with great caution before admitting to Holy Orders those candidates unable to ingest alcohol without serious harm.
- Attention should be paid to medical advances in the area of alcoholism and encouragement given to the production of unaltered mustum.
- Congregation for the Doctrine of the Faith: circular letter Prot. 89/78-174 98 of 24 July 2003 to Presidents of Episcopal Conferences
- "The Use of Mustum and Low-Gluten Hosts at Mass". United States Conference of Catholic Bishops. November 2003. http://www.usccb.org/liturgy/innews/1103.shtml. Retrieved 2008-08-05.
- Summa Theologica, III, q. 74, art. 5, reply to objection 3
- Further information from the USCCB's Committee on Divine Worship
- Further information from the Liturgy Office of the Catholic Bishops' Conference of England and Wales