Physical properties and processing of Silphium integrifolium seeds to obtain oil and enriched protein meal

Abstract

Silphium integrifolium Michx. (Silflower) has been a promising subject for domestication as a perennial oilseed crop. This work was carried out to investigate the seed processing aspect of this effort. Thousand seed weight, densities, and dimension of the seeds were evaluated, seed milling to obtain enriched kernel fraction was conducted, and initial characterization of the seed protein was performed. There was wide variation in flat seed length (11.5–20.8 mm), width (4.6–11.8 mm), and thickness (0.9–1.6 mm). The thousand seed weight was 23.8 g but the tapped bulk density was only 189.6 g/L due to the presence of wing around the seed's periphery. The kernel accounted for 56.1% of the seed weight and contained 31.0% oil. A kernel-enriched fraction with 79.6% purity was obtained by roller-milling, sifting, and air classification. Linoleic (62.3%) and oleic (19.6%) acids were the major fatty acids in the oil. The defatted enriched kernel fraction contained 63.41% crude protein. Globulin, glutelin, albumin, and prolamin accounted for 55.6%, 19.3%, 16.4%, and 8.7% of the soluble proteins, respectively. At an extraction pH of 9, protein solubility was 62%. Maximum solubility (70%) was obtained at pH 10 while minimum solubility of 9% occurred between pH 4 and 5.5. Aside from the oil, the dehulling of silflower seeds also produced a high-protein defatted meal, which may be used as is or as a starting material for enriching the protein further into a protein isolate.