Q: Is there a standard for the type of wine to be used at Mass? Is a “jug” wine acceptable? This is for a low income, struggling parish.
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A: See Redemptionis Sacramentum 50: https://www.vatican.va/roman_curia/congregations/ccdds/documents/rc_con_ccdds_doc_20040423_redemptionis-sacramentum_en.html
And this letter: https://www.vatican.va/roman_curia/congregations/ccdds/documents/rc_con_ccdds_doc_20170615_lettera-su-pane-vino-eucaristia_en.html
For questions of validity, please consult a canonist, but most people I know worry that jug wine has additives that alter its properties. It needs to be wine made only from grapes.