This recipe is best made with ripe strawberries, which will make the bread very flavorful. If the strawberries aren't ripe, it's best to wait until you have ripe strawberries for optimum flavor. If you'd like to proceed anyway, I recommend using a stand mixer with a whisk attachment to beat the berries into the oil and egg mixture. A hand mixer will likely not be powerful enough if the berries are a little hard and/or white inside.