Turn refrigerator control to coldest setting.
Sprinkle gelatin on 1/4 cup of the water and let stand for 5 minutes.
Mix remaining 1/2 cup water, pineapple juice, and sugar; boil for 3 minutes.
Add gelatin and stir until dissolved.
Add remaining ingredients except last 2.
Pour into refrigerator tray and freeze until mushy.
Turn into chilled bowl; add unbeaten salted egg whites and whip until stiff.
Pour into refrigerator tray and freeze until firm.
Serve garnished with mint sprigs.