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Effects of Break-Roll Speed Differential on Product Yield and Semolina Granulation in a Durum Pilot Mill System

¹Research Food Technologist, USDA/ARS Wheat Quality Laboratory, North Dakota State University, Fargo, ND 58105. Phone: 701/231-7728. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.

Changes in break-roll speed differential in a 25-quintal (55-cwt) durum pilot mill system (136 kg/hr feed rate capacity) affected total yield of semolina, flour, and bran; semolina yield from different purifiers; and semolina granulation (150- to 841-μm particle size range). By adjusting the speed differential of the break and chunk roll pairs from 1.5:1 to 2.5:1 to 3.5:1, semolina yield increased significantly from 55 to 67 to 72%, respectively, and bran yield decreased significantly from 24 to 15 to 11%, respectively. Shorts yield was not affected by speed differential. At 1.5:1, semolina contained 9% flour, compared with 5% flour at 2.5:1 and 3.5:1.