Preparation, De-colorization, and characterization of protein isolate from Silflower (Silphium integrifolium Michx),...

Silflower, the perennial sunflower from North American prairies, presents multiple agronomic benefits fostering interest in domestication. Silflower seeds contain ∼368 g/kg proteins, but the undesirable color of extracted proteins arising from protein/phenolic interactions limits their food applications. Hereby, we present the first investigation on the preparation, de-colorization, and characterization of silflower protein isolate (SiPI). Extracting at pH 9.5 recovered 52% of proteins from seeds but conferred SiPI a dark color accompanying total phenolic content of 3.28 mg/g gallic acid equivalent. Extraction at pH 6.0 with NaCl and optionally absorbent resins reduced phenolic content by up to 68% and increased brightness by up to 32%. SiPI contains ∼59% β-secondary structures and comprises subunits analogous to sunflower 11S and 2S proteins. Thermal denaturation and decomposition commence at (89-104) and (251-255) °C, respectively, depending on extraction procedure. This study paves the way for practical applications of SiPI and comprehensive utilization of silflower plants.