Mechanistic insights into enhancement of sunflower protein isolates through a combined fractionation and fungal bioprocessing of sunflower meal

Authors: THAPA, SANTOSH - South Dakota State University; Brownstein, Korey; MCTAGGART, ROBERT - South Dakota State University; KARKI, BISHNU - South Dakota State University

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2025
Publication Date: 12/2/2025
Citation: Thapa, S., Brownstein, K., McTaggart, R., Karki, B. 2025. Mechanistic insights into enhancement of sunflower protein isolates through a combined fractionation and fungal bioprocessing of sunflower meal. LWT - Food Science and Technology. https://doi.org/10.1016/j.lwt.2025.118846.
DOI: https://doi.org/10.1016/j.lwt.2025.118846

Interpretive Summary: We developed an integrated green processing approach to improve the properties of sunflower protein isolates (SPIs) for food applications, addressing the challenges of protein extractability and the presence of phenolic compounds in sunflower meals. The combination of size fractionation and fungal fermentation with Aspergillus oryzae and Aspergillus niger proved to be an effective and sustainable approach to reducing phenolic compounds and enhancing the SPIs solubility, making them more suitable for a range of food applications. These findings address key challenges in protein extractability and phenolic content, providing valuable insights for developing high-quality, eco-friendly plant protein ingredients. This integrated approach paves the way for more efficient, functional, and sustainable plant-based proteins in the food industry.

Technical Abstract: Sunflower meal (SM) is an affordable, balanced, and hypoallergenic plant protein source; however, its low protein extractability and phenolic compounds limit functionality, digestibility, color and flavor. Therefore, removing phenolics and modifying proteins are essential for food applications. This study evaluated the impact of size-fractionation and fermentation of SM (Aspergillus niger and Aspergillus oryzae) on the physico-chemical, molecular, and functional properties of sunflower protein isolates (SPI). Coarser SMs (>0.25 mm) were fiber-rich, whereas finer SMs (<0.25 mm) contained higher protein, phenolics, and flavonoids. SPIs from finer SMs exhibited lower protein-purity but higher phenolics, flavonoids, and lighter color. Autoclaving reduced protein-extractability, and purity, but increased phenolics, flavonoids, chlorogenic and caffeic acids and altered SPI’s molecular and secondary structure, whereas gamma-irradiation mitigated these effects. Fermentation with Aspergillus niger enhanced protein extractability but did not improve protein recovery or purity. Both fungi reduced phenolics, flavonoids and chlorogenic acid and protein molecular weight. SPIs from fermented SM significantly enhanced SPI solubility (up to 22.8 % and 151.2 % in autoclaved and gamma-irradiated SM, respectively) and surface-hydrophobicity (up to 133.8 % in gamma-irradiated SM), although color, particle-size, zeta-potential, foaming, and emulsifying properties were unchanged. These findings demonstrate that size-fractionation and fermentation significantly influence protein extraction and SPI characteristics.