What is the preferred form of food for expiation: whole grain or flour?

Primary text

The preferred form according to Abu Abdullah (Ahmad) is whole grain (Habb) because it avoids scholarly dispute and represents the food in its state of perfection, allowing for storage and full utility. If flour (Daqiq) is given, it is valid, provided the amount exceeds the measure of a Mudd by a quantity equivalent to the weight difference in whole grain, or it must be given by weight, as whole grain possesses a residual value (Riy').