What renders the bread & wine into invalid matter?

[Rob_in_Oregon]

What substance, added to unleavened wheat bread, would render the bread into invalid matter for consecration? The Eastern churches add yeast, and their Eucharist is valid. What about sugar? Would the bread consecrate alongside unconsecrated sugar? At what point does the whole mix become invalid? God bless… - Rob in Oregon

 

[Don_Ruggero]

The bread should be made from wheat flour which is mixed only with water and baked. Beyond that, one should not introduce other ingredients precisely so as not to render the matter doubtful and, eventually, invalid.

The practice of the West moreover is well stated in our Code of Canon Law.

“Can. 926 According to the ancient tradition of the Latin Church, the priest is to use unleavened bread in the eucharistic celebration whenever he offers it.”