Sweet, fortified wine. The production of fortified wine was introduced in 1934, and in 1944, the Rasteau AOC for VDN wines was created. Main grape varieties for the fortified wines are Grenache Noir, Grenache Gris and Grenache Blanc. A vin doux naturel wine must reach a minimum alcohol content of 15%, with the maximum being 21.5%. Ageing in concrete beton tanks.