Combine water, replacement and cornstarch in a saucepan. Bring to a boil and reduce to a simmer. Simmer for 5 minutes and stir in the puree and lemon juice with the food color. Pour into freezer trays, cover with wax paper and freeze. For a fluffy texture freeze until mushy. Scrape into a mixing bowl and beat until just loosened. Return to tray and freeze.  Recipe makes 4 servings at 14 calories each.