Peter NEVER ASKED FOR THE BREAD...He said that Jesus had the WORDS of eternal life...not the bread
The disciples who believed Jesus and were 'down for the whole mission' spoke of the Words of Eternal Life, not bread or manna or blood drinking. Those who walked away were focused upon the flesh and the blood and they were so focused on what they could do to be worthy that the violation of the laws of Moses eliminated Jesus as anything they would follow.
I mean, look at what they asked Jesus: 'what works must we do?'! It's the age old barrier that secret pride in self erects, looking for how to do it for God or how to do it to be worthy of Grace, as if what they can do is going to get accounted for them in some weighing exercise, or their good livin' will outweigh the bad livin'.
The ones who walked away had asked 'what must we do to earn this bread, this forever food from God?' Jesus's answer didn't suit their self pride, so they settled upon the law as their shield from seeing the Truth of what Jesus was telling them, that just believing is what God requires. When that didn't suit them, Jesus used sarcasm to drive them out all together.
The Jews had reached the point that even their Passover meals were not spiritual but exercises in Pride at being the chosen people. What Jesus came to do was fufill the alw the Jews beleievd would weigh them worthy of eternal life. It cannot, as Paul explained over and over.