Luke 24:31

‘And their eyes were opened, and they knew him, and he vanished from their sight.'

And it was when He performed this action that their eyes were opened and they knew Him, and He then, seemingly immediately, disappeared from their sight. It is very probable that they had a number of times been present at meals where Jesus had blessed the bread, and had broken and distributed it, and had therefore recognised the way in which He did it. And the very placing of Him in a context that they recognised would help with the recognition. This then opened their eyes to the fact that the Stranger was not just somewhat similar to Jesus, but really was Jesus. The impression is given that He did not partake of the bread. This sudden disappearance stresses the deliberate nature of His revelation of Himself to these two disciples, and made clear that He was not there as someone who had just come back again. He was there as One Who had risen from the dead and belonged to another world. Once He was satisfied that they knew Him He departed mysteriously, His task accomplished. And they would be continuing witnesses to the resurrection in Jerusalem and Judea once the Apostles had gone.