Optimizing the Debranning of Wheat for Ethanol Production

Abstract

Debranning is employed on wheat grains used as feedstock for ethanol production to increase its starch content for subsequent milling, fermentation and downstream processes in an ethanol plant. Experiments were carried out to abrasively remove the bran layer of wheat using two debranning equipment, the Satake mill and tangential abrasive dehulling device (TADD) in order to optimize the debranning process. Thirty gram samples of wheat grain were debranned in the Satake mill at grit sizes of 30, 36 and 40, retention time of 30, 60 and 90 s and rotational speed of 1215, 1412 and 1515 rpm or in the TADD at grit sizes of 30, 36, 50 and 80, retention time of 2, 3, 4 and 5 min and rotational speed of 900 rpm. The result indicated that debranning using abrasive disc of higher grit size (fine grit) resulted in a decrease in the percentage removal of bran: long retention time caused a high amount of bran to be removed. This, in turn, would lead to an undesirable decrease in starch content of the kernel. Starch separation efficiency was used to optimize the processing conditions. The study indicated that grit sizes 30 or 36, a retention time of 60s and a rotational speed of 1515 rpm were optimum to produce the desirable amount of bran for Satake mill and grit size 80 was optimum to produce bran in TADD but bran obtained for retention time 2, 3, 4 and 5 min in TADD was low. Based upon starch separation efficiency, the optimized conditions for the Satake is more desirable compared to TADD.