You evidence some of the possible misunderstanding of Thomas that bothers me.

Thomas' "substantia" (Aristotle's) is not actually very 'substantial'. It is a Mental Category. People make him say something he is not actually saying.

True, the 'reality' of our 'mental category' is different for a believer who understands the Eucharistic bread and wine to be a communion with and in the death and resurrection of the Risen and glorified Jesus.That we are present to Jesus: "whole and entire, body and blood, soul and divinity".

That is quite different than believing that there is a hunk of 'flesh'  – heart muscle or any other body part –that just looks like bread; or 'blood' apart from a body, that happens to taste like wine.

St. Thomas does NOT say 'bread and wine cease to exist'. He says their 'acccidentia' continue. That's not the same as our English 'accident'. Everything we call 'real' is the same: taste, look, feel, chemical makeup.

We easily mis-represent actual Church teaching.