Blood Orange Sherbet

1/3 cup granulated sugar
1 cup water
2 cups strained blood orange juice
2 teaspoons fresh lemon juice
2 teaspoons finely-grated blood orange zest
2 tablespoons orange-flavored liqueur or vodka (optional)
3 large egg whites, beaten until stiff

Combine sugar and water in a small saucepan and heat until sugar is melted and mixture is clear. Remove and chill.

In a glass bowl, combine chilled sugar syrup, orange juice, lemon juice, zest and liqueur. Mix thoroughly, then fold in the egg whites using an over-and-under motion. Continue folding until no egg white streaks remain in the mixture. Pour mixture into an ice cream maker and freeze until firm, according to manufacturer's instructions.

Makes about 1 1/2 pints.