Preheat oven to 400°F Lightly coat a baking sheet with cooking spray.
Place cream cheese in a small bowl and stir until completely smooth.
Separate the egg yolk from the egg white. Place the egg white in a small bowl and add the egg yolk to the cream cheese. Add 1/4 cup sugar and lemon juice to cream cheese and combine.
Lay puff pastry on a flat surface and cut into nine small squares. Spoon about 1 tablespoon of cream cheese mixture diagonally down the center of each square from one corner to the opposite corner. Press the blueberries into cream cheese.
Fold the sides into the center, wet the points with a little water and press tightly to seal. (Press sides tightly together or they will open while they bake).
Place turnovers on the baking pan, brush with egg white and sprinkle lightly with the sugar and cinnamon.
Bake for 15 minutes until golden brown. Remove from oven and serve warm.