Performance analysis of a dehulling system for safflower grains

The performance of a dehulling system for safflower grains was analyzed in terms of the dehulling ability (DA) and the percentage of the fines generated (F, broken grains with a diameter smaller than 2 mm). For this study, six American safflower cultivars were selected, namely CW 99 OL, S-5344, S-3125, L75, L8 and Knowles93079. Response surface methodology (RSM) was used to optimize the operating conditions, and desirability function was used as the methodology for the optimization. The independent variables were impact dehuller rotor speed (rpm), which was expressed in terms of the peripheral speed of the impeller (m/s), and grain moisture content (%, d.b.). For all the safflower cultivars, second order polynomial models were developed for both studied responses (DA and F). The results of the optimization technique revealed that the best dehulling performance could be obtained if the system is operated at a peripheral speed of 40.5 m/s with a grain moisture content in the range 8.4–8.9% d.b. Under these conditions, the maximum values of DA would be obtained with a percentage of fines of less than 2% for all the safflower cultivars, except L8. The processing of L8 under these operating conditions would also lead to optimal values of DA with an industrially acceptable percentage of fines (from 1.8 to 3.1%, d.b.). The percentages of residual hull were also calculated, and they were higher than the recommended values for a proper bed porosity (10–12%) for oil extraction with solvent. These results suggest the need to evaluate other process variables in order to achieve an appropriate hull content for the oil extraction bed.

► Safflower oil shows a growing importance for nutritional and pharmaceutical purposes and due to its use as biofuel.
► In the oil industry, partial dehulling of the grains prior to the oil extraction stage must be performed.
► This paper investigates the performance of a dehulling system for safflower grains.
► An optimum combination of the operating conditions (moisture content and peripheral speed) was obtained.
► Maximum values of dehulling with acceptable percentages of fines were obtained.