They don't chew. Chewing is what land animals who eat leafy plants do.

They can bite, and that's about it. Do these look like chewing teeth? http://4everstatic.com/pictures/674xX/animals/aquatic-life/d...

Dolphins haven't developed the kind of jaws necessary to chew substantially like a human, who chews with molars. Also humans still can choke to death on octopus.

I wager that the whole purpose of throwing the tentacles into the air is to provide the dying organism with a lack of stimulus to the neurons in the tentacles for a few seconds, on water impact, the renewed stimulus would make the tentacles move. I reckon after a few tries the tentacles just run out of energy.

This is just a thought and may not be correct.