Even if the purported flesh and blood is real, that is no evidence that it is the end result of any miraculous transformation of bread and wine. That proposition cannot be verified since the only evidence for it is the say-so of a monk some twelve centuries ago. Prior to the very recent permission granted to professional researchers to examine the Shroud, the only examinations had been performed by the Church itself. Needless to say, they reported that there was real blood in the image. Now, after competent examination has proven otherwise, the position of the Church is that the Shroud is still a holy relic and is an article of faith for Catholics.
Old habits die hard.
I have, and I never do otherwise. The apparent reddening comes from light being more readily transmitted through the liquefied substance. The emotional appeal of a good story is no indication whatsoever that it is true. Given the number of claimed miracles, this abysmal track record casts extreme doubt on the veracity of any purported miracle which may still remain unexplained. I fully realize that not every story of a miraculous happening is worthy of belief, but these are incredibly well documented and have never, so far, been proven to be caused by anything found in nature.