Transubstantiation is a concept that Roman Catholic scholastics, most notably Thomas Aquinas, developed for the doctrine of Communion. Catholics state that when a priest blesses the elements of bread and wine, they become the body and blood of Christ.
Catholics admit that chemically they would still be considered bread and wine. But they believe nonetheless that the elements have ceased to be bread and wine and have been converted1 into flesh and blood. They say that the substance has been converted1 (hence the term transubstantiation) but that the accidents of the bread and wine remain as they were. Those accidents include all the ways the senses (touch, taste, etc.) interact with the elements, and all the ways a chemist (for example) would classify the elements in the absence of knowing that a priest has blessed them.
The categories of substance and accidents were borrowed from Aristotle. My question is, is transubstantiation faithful to his categories? I'm not asking if it was intended to be - I think Catholics are aware that they may have borrowed philosophical concepts from others and changed them for their own use - I'm asking if Aristotle's formulation of those concepts is consistent with the philosophical defense of transubstantiation. Specifically, I want to know, if nothing changed outwardly about those elements, could the substance still be said to have changed (from Aristotle's perspective) as Catholics say it could?
1 Originally this question had "transformed" and not "converted." This was sloppy terminology, as transformation would mean a change of shape or form, which is expressly not what happens in transubstantiation. "Conversion" is a better term.