[Question:]{.underline} Are the brown hosts frequently used in the Novus Ordo validly consecrated, or must the hosts be white?
[Answer:]{.underline} It is Canon 815, §1 (1917 Code) that determines the valid matter that must be used for the consecration of hosts. It is only “pure wheaten bread” that is apt for consecration into the Body of Christ at Mass. Canon 924,§2 of the 1983 Code says the same thing. Consequently bread baked from flour made out of any variety of true wheat is certainly valid matter, whereas flour made out of any non-wheat cereal is certainly invalid matter, such as that made from rye, barley or millet, as is also bread baked with a notable quantity of non-wheaten flour. (Matters Liturgical, p. 320). If anything other than pure water and wheaten flour is included in the mix, then it is of doubtful validity. Likewise if the bread is old and stale and in danger of corruption. Such things are strictly illicit and forbidden.
The usual reason why the hosts used are brown is that they are baked out of whole-wheaten flour. Such matter is valid and licit, provided that (in the Latin rite) the dough is unleavened. Consequently, it will not in itself be a reason to doubt the validity of the Mass, unless there is a suspicion that other elements (e.g. eggs or butter or sugar) were added. However, it is most inappropriate to use brown hosts. The whiteness of the host represents the purity of the Immaculate Victim, the perfect Lamb of God, whose perfect offering of Himself is renewed in an unbloody way on the altar. It is most inappropriate for this symbolism to be blemished by the use of whole meal flour for the baking of altar breads.
Answered by Father Peter Scott, SSPX.