Performance of centrifugal dehulling system for sunflower seeds

Engineering properties and optimization of the dehulling process for hairless canary seed

 This work aimed to determine the engineering properties of hairless canary seeds (Phalaris canariensis L.) of the variety "CDC Maria" and the optimum combination of operating conditions of the dehulling process with a pilot-scale centrifugal dehuller. The engineering properties analyzed in this study were the principal dimensions, length (4.8 mm), width (1.95 mm) and thickness (1.41 mm); geometric mean diameter (2.36 mm); the sphericity (49.2%); apparent and true densities (752 and 1191.47 kg/m3, respectively); the porosity (0.37); 1000 grains weight (7.28 g); angle of repose (15.89°) and the static coefficient of friction (galvanized steel, 0.325; plywood, 0.372; aluminium, 0.316). For the process optimization, a two-variable Doehlert design was used, analyzing the effect of impact dehuller rotor speed (peripheral speed 30.4 to 47.1 m/s) and seed moisture content (10 to 14% d.b.) by maximizing the dehulling ability (DA) and maintaining the production of fines by 3%. Under the experimental conditions of 36.7 m/s (peripheral speed) and 10% d.b. (seed moisture), with a double pass through the dehuller, the optimum value of DA (94%) was obtained, with a fine production of 3%. The optimized dehulling process allows removing a large percentage (98%) of the canary seed hull.

Design and development of annatto (Bixa orellana L.) seed separator machine

A small, continuous power operated machine with a capacity of 132 kg/h was designed, fabricated and evaluated its performance for separation of annatto (Bixa orellana L.) seeds from freshly harvested pods. Physical and engineering parameters of annatto pods and seeds were evaluated to design a machine. The densities of pod, seed, and husk are 134.7 to 186.0 kg/m(3), 1206 to 1253.9 kg/m(3), 317 to 381.4 kg/m(3) respectively. The moisture content of seeds were in the range 18.83 - 20.1 % (db) and pod 8 to 10 % (db). Bixin content of seed was in the range 1.34 to 1.765 %. The friction angle for pod, seed, and husk lies between angle 30.15° to 35.76°. Breaking force was 98 N at a span of 14.5 mm. The machine consisted of concentric cylinders and beaters with different pitch of 40, 45 and 50 mm and a length of shaft is 800 mm. The actual machine output was observed to be 132.5 kg/h. Maximum bixin content was found to be retained at 300 rpm.

Loss of lipid material during the dehulling of oilseeds with different structural characteristics

The loss of lipid material by migration to the hull during the dehulling of oilseeds with different structural characteristics was evaluated. The samples selected -three sunflower hybrids and a safflower cultivar- were processed under optimal dehulling operating conditions and with two passes through a dehuller. From the SEM micrographs of the samples it was possible to observe structural differences which affect the mechanical properties of the pericarps and, consequently, the dehulling process. The black-hull sunflower hybrid exhibited residual hull percentages lightly above those recommended by the industry after one pass through the dehuller, therefore, this hybrid should not be further processed to avoid oil losses due to migration to the hull. On the other hand, the safflower cultivar and the high stearic high oleic sunflower hybrid and the traditional striped-hull sunflower require two passes through the dehuller, but this resulted in an oil loss due to migration to the hull of over 0.9 % per gram of grains processed. These results suggest the need to reach 'compromise' decisions based on economic impact studies in the face of the variables that originate simultaneously both positive and negative effects.