Rinse the rice briefly in a sieve; for a creamier pudding skip the rinse.
Put the rice, milk, maple syrup and cinnamon in a heavy saucepan and bring to a gentle simmer over medium heat, stirring so the milk does not catch.
Reduce the heat to low and simmer uncovered for 25 to 30 minutes, stirring every 2 to 3 minutes and scraping the bottom, until the rice is tender and the pudding is creamy.
Take the pan off the heat and cool for 5 minutes; casein clumps if added to boiling milk.
Whisk in the casein protein and vanilla until smooth, then stir in the raisins.
Serve warm, or chill; it thickens in the fridge, so stir in a splash of milk before eating. Keeps 4 days.