This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Bran. Bran contains considerable cellulose and cellulose absorbs water slowly. Rahn describes the Schlueter process by which bran is steeped in hot water and treated for some time with moist heat. During this treatment the cellulose membranes are sufficiently hydrolyzed so that the cell contents are more readily digestible. The bran is then dried and put through a crusher and a fine grinding mill. In contrast to ordinary bran, the treated bran is said to keep indefinitely and absorbs water more readily and in larger quantity.