Soy Bran is fibre from soybean hulls.
The hull is about 8% of the beans weight, and ⅓ of the hull is fibre, most of which (over 70%) is digestible by humans. It is extracted from the hull and refined.Argentina is a major exporter of soy bran for use in animal food.
History Notes
The hulls of soybeans used to be just fed to livestock, and never had a name. The term was coined in 1919 by an American named W.G. Bowers to refer to hulls that had been pulverized, and were intended for human consumption.
The term didn’t really have any use, though, until 1979, when a commercial product with soy bran in it was launched by the Archer Daniels Midland Company. It was meant to be used in baked goods, as you would wheat bran.