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. Aquinas himself declared: