Use this grenadine for the Canton cocktail.Plus: Ultimate Cocktail Guide
In a large saucepan, combine the pomegranate juice, superfine sugar and pomegranate seeds and simmer until the juice has reduced by half. Let cool, strain into an airtight container and stir in the citric acid powder. Refrigerate for up to 1 month.
Citric acid, which is found in many kinds of fruit, preserves food and adds acidity. It's available in powdered form at health food stores.