Pureed raisins maintain the moisture of eggs and work to bind together ingredients when baking a cake or a bread. They also add a tang to whatever you are baking. Dates also work in this recipe.
When using Chia or Flax seeds the conversion is as follows:
1 egg = 1 tbsp of ground flax seed/Chia seed + 3 tbsp water
Let the mixture set in the fridge for 15 minutes, stir.
This forms a jelly-like substance.