Angel fish spits his food out - why?

[Last Triumph]

Angel is recovering from hole in the head - ulcers are now almost completely healed.
He has not eaten in two weeks now.
Tonight for the first time I saw him try some frozen bloodworm (favourite), but he chewed it for a few seconds then spat it out.
He then did it again a minute later then gave up and swam off, ignoring the other food floating around him.
Why won't he swallow his food?

[TropicalFishForums]