I was having dinner with a priest the other night and he made a comment that the use of mustum is “no longer being allowed.” I was wondering if this was a universal sanction, or whether it may be a Diocesan rule only. I understand that this would represent simply a change in practice, and not be a declaration of mustum being invalid matter.
Composition of Mustum
On June 19, 1995, Cardinal Joseph Ratzinger, Prefect of the Congregation for the Doctrine of the Faith, addressed a circular letter to Presidents of Episcopal Conferences containing revised procedures for permitting the use of mustum to priests affected by alcoholism (Prot. N. 89/78). In recent months the Secretariat has received inquiries from several dioceses whose Ordinaries have granted permission for the use of mustum to priests adversely affected by even a small amount of alcohol. The correspondents have sought a more precise definition of mustum.
Article II-C of Cardinal Ratzinger’s letter describes mustum as “fresh grape juice from grapes, or juice preserved by suspending its fermentation (by means of freezing or other methods which do not alter its nature).” While several brands of grape juice are available commercially, not all varieties meet the requirements of mustum.
Any commercially produced grape juice whose fermentation process was arrested, even at a very early stage, may be used for mustum. However, those grape juices which have been pasteurized are not proper matter for Eucharist because such pasteurization removes even trace amount of alcohol produced in the natural fermentation process.
The insistence on the purity and integrity of the grape juice used as mustum is to assure that the matter used for the Eucharist retains, as closely as possible, the characteristics of the matter intended by Christ to become his own Precious Blood.
Source: Committee on the Liturgy USCCB
Norms for use of Low-Gluten Bread and “Mustum”
By Cardinal Ratzinger