- Undo the stalks from the celery. With a centrifugal juicer, extract the juice from the celery. You'll need 500 ml (2 cups). Proceed the same way with the apples. You'll need 250 ml (1 cup). It is better to extract the apple juice directly into a container with the lime juice to prevent oxidation.
- In a saucepan, heat the apple juice and lime juice with the sugar until it dissolves. Add the celery juice and skim thoroughly.
- Pour into a 20-cm (8-inch) glass dish. Cover and freeze for 8 hours or until the granita is completely frozen. With a fork, scrape the surface of the granita to break into crystals. Serve immediately in sundae bowls.