Vatican asks bishops to ensure validity of matter for Eucharist: VATICAN CITY (CNS) -- Bishops should look at ways to help verify and guarantee the validity and worthiness of the bread and wine used for the celebration of the Eucharist, the Vatican said in a recent interview.
This article from the Pilot is about checking the ingredients:
"The bread used in the celebration of the most holy eucharistic sacrifice must be unleavened, purely of wheat, and recently made so that there is no danger of decomposition.
-- Wine used in the celebration of the eucharistic "must be natural, from the fruit of the grape, pure and incorrupt, not mixed with other substances," well conserved and have not soured.
There are few exceptions and with stipulations. Read the article for the specifics.