Place pineapple chunks in a blender or food processor, and process until smooth. Combine the pineapple purée, 3 cups pineapple juice, and next 4 ingredients (pineapple juice through coconut extract) in a large bowl. Pour mixture into a 13 x 9-inch baking dish; cover and freeze at least 8 hours or until firm.
Remove the frozen pineapple mixture from the freezer. Scrape the entire mixture with a fork until fluffy. Spoon the mixture into a freezer-safe container; cover and freeze up to 1 month. Garnish with mint sprigs, if desired.
