Enhanced color and antioxidant properties of sunflower protein concentrates extracted under alkaline conditions using anti-greening reagents

Sunflower protein concentrates (SPCs) are valuable plant-derived ingredients. However, their application is limited by greening during alkaline extraction, caused by chlorogenic acid (CGA) oxidation. This study systematically developed and characterized SPCs extracted under alkaline conditions with two anti-greening reagents, N-acetylcysteine (NAC) and ascorbic acid (ASC), each applied at 12 mg g^-1 meal. The findings provide novel insights into how these reagents modulate the amino acid composition, structural conformation, and antioxidant potential, and improve color in SPCs obtained from completely hulled (SPC-CH) and unhulled (SPC-UH) sunflower seeds.

The addition of ASC during extraction increased the total phenolic content to 130.51 g kg^-1 CGA in SPC-CH and 119.08 g kg^-1 CGA in SPC-UH. The antioxidant capacity, measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, reached 1084.38 mmol kg^-1 Trolox equivalent (TE) in ASC-treated SPC-CH, compared with 891.08 and 937.58 mmol kg^-1 TE in the distilled water (DW) and NAC treatments. Both ASC and NAC inhibited greening, producing SPCs with a more acceptable yellowish color. Structural analysis showed only minor alterations in protein secondary structure across all extraction methods, indicating that protein integrity was maintained. Thermal stability and amino acid composition evaluations further supported the suitability of these SPCs for food applications.

The use of ASC and NAC as anti-greening reagents improved the color and antioxidant potential of sunflower protein concentrates while maintaining structural stability. This approach enables the sustainable production of high-quality SPCs, suitable for functional food formulations. © 2025 Society of Chemical Industry.