Dual exploitation of Silflower (Silphium integrifolium Michx) seeds to produce a protein isolate and a phenolic-rich extract

Authors: Teng, Zi; Arther, Christina; Brownstein, Korey; Singh, Mukti; Liu, Sean

Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/27/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Silflower (Silphium integrifolium Michx) is a perennial oilseed crop native to the central United States. It is undergoing increased interest in domestication due to its drought tolerance and competitiveness with annual weeds. Defatted silflower meal is rich in proteins (48.6%) and phenolics (5.28 mg GAE/g), but the interactions between those compounds give silflower proteins an unpleasant dark color, which limits the application of silflower proteins in food products. In this study, a two-step extraction process was developed to produce a phenolic-rich fraction (PhF) and light-colored protein isolate (SiPI), allowing comprehensive valorization of this emerging cash crop. Defatted silflower seed meal (DFM) was extracted with 70% ethanol to produce the PhF, which recovered >80% of the phenolics from DFM. The PhF exhibited high total phenolic content (TPC, 56 mg GAE/g DW), chlorogenic acid level (11 mg/g DW), and ABTS antioxidant activity (205 µmol Trolox per g DW). The solid residue after ethanolic extraction was further extracted at pH 8.0 with 0.8 M NaCl and 0.01 M NaHSO3 to produce de-phenolized SiPI (DP-SiPI). A conventional method of extracting DFM directly at pH 9.0 followed by isoelectric precipitation was employed to produce control SiPI (C-SiPI). DP-SiPI showed significantly higher brightness than C-SiPI (L* = 74.8 vs 62.4), together with less greenness (a* = 5.17 vs 2.48), and less blueness (b* = 26.1 vs 16.5) than C-SiPI. DP-SiPI also showed very low level of phytic acid at 1.2 mg/g, compared to 4.4 mg/g for C-SiPI and over 10 mg/g for soy protein isolate. On the other hand, DP-SiPI showed moderately lower protein recovery from DFM at 32% compared to 40% for C-SiPI. Additionally, DP-SiPI also has an amino acid score (AAS) of 0.77 with lysine being the limiting amino acid, whereas C-SiPI is a complete protein with AAS of 1.00. Both DP-SiPI and C-SiPI contain 28% ß-sheets and 24% ß-turns, and they comprise subunits resembling the 11S globulin and 2S albumin in sunflower seeds. DSC measurements indicated two denaturation peaks at 90 and 110 °C, respectively. This study demonstrates the feasibility of multifaceted utilization of silflower, an emerging oilseed crop in the United States. It provides an integrated approach to recovering both the health-benefiting phenolics and nutritious, visually appealing proteins from silflower seeds besides oil.