Research from the internet reveals two things that could possibly be true about fruit pectin. 1)PROLONGED heating will gradually destroy the pectin. 2)Pectin is related to improved flavour.
To test these ideas Anne cooked some frozen blueberries and added a little corn starch. Overcooking was avoided. The cooked blueberries were allowed to cool for a few minutes and then poured into a precooked pie shell. A layer of frozen Duke blueberries were added followed by another layer of cooked blueberries. Click on pictures to enlarge.
frozen berries added 
more cooked berries The pie was allowed to cool and refrigerated for a couple of hours. The picture below shows how nicely it jelled. The layer of frozen Duke berries added a nice texture to the pie. Taste tests are ongoing but results so far are promising. More tests are needed. This is fun!
blueberry pie 