What does this have to do with the Eucharist? This is my body; this is my blood. When God says something IS, then it IS, regardless of what we say, see or taste. In fact, if there was some physically measurable change with the bread and wine, it would contradict Church teaching.
When Jesus says to do this in remembrance of Him, we obey. Jesus has the proper authority and he passed it on to his apostles, “As the Father has sent me, so I send you” (John 20:21). This verse begs a question; how did the Father send Jesus? With all the authority in heaven and on earth (see Mat 28:18). I'd say that’s an impressive amount of authority to pass on. What say you?