50.] 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.127 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.128 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.