Preheat oven to 180 C / Gas mark 4. Lightly grease a 20x10cm (8×4 in) loaf tin.
In a large bowl, stir together flour, sugar, baking powder, bicarbonate of soda and cinnamon. Add egg whites, bananas and apple purée; stir just until combined. Pour batter into prepared tin.
Bake in preheated oven for 50 to 55 minutes, until a knife inserted into centre of loaf comes out clean. Turn out onto cooling rack and allow to cool before slicing.
