When you freeze raspberries, they need to be perfectly prepped. Firstly, remove any stems and discard any unripe or damaged berries. Rinse the raspberries under cool water and brush away any dirt. To dry them thoroughly, lay them out on kitchen towel and pat dry. Homemade raspberry coulis is always a summer winner and when made fresh, it can be stored in the freezer either in ice cube trays or in a freezer bag.