The fermentation with its long rising period add to the taste of this rye bread, give it a moist texture, and keep it from drying out. You can make a double quantity of the ferment, and keep the rest in an air-tight container in a freezer or a fridge. Bread made solely from rye flour is heavy and dense and does not rise very well. This is why rye flour is usually mixed with wheat flour in equal measures. Though the taste of rye will predominate, the bread will rise better and will therefore be more 'airy'.