How did the disciples recognize Jesus on their way to Emmaus?

That He was the messiah who had to suffer, die and be resurrected to life again:

Luke 24:22-27New International Version (NIV)

22 In addition, some of our women amazed us. They went to the tomb early this morning 23 but didn't find his body. They came and told us that they had seen a vision of angels, who said he was alive. 24 Then some of our companions went to the tomb and found it just as the women had said, but they did not see Jesus."

25 He said to them, "How foolish you are, and how slow to believe all that the prophets have spoken! 26 Did not the Messiah have to suffer these things and then enter his glory?"27 And beginning with Moses and all the Prophets, he explained to them what was said in all the Scriptures concerning himself.