Place bananas in freezer and freeze overnight. Remove bananas from freezer and allow to thaw for 45 minutes to 1 hour. Peel bananas and place in bowl of food processor along with the lemon juice. Process for 10 to 15 seconds. Add corn syrup and vanilla bean seeds and turn processor on. Slowly pour in the heavy cream. Process until smooth. Chill mixture in refrigerator until it reaches 40 degrees. Transfer mixture to an ice cream maker and process according to manufacturer's instructions. Place mixture in an airtight container and freeze for 3 to 6 hours before serving.
Recipe courtesy of Alton Brown, 2003