Effect of Size Fractionation and Submerged Fungal Fermentation of Sunflower Meal on the Protein Isolates — 89p — Santosh Thapa¹, Robert McTaggart², William R. Gibbons¹ & Bishnu Karki¹

¹Department of Biology and Microbiology, South Dakota State University, Brookings, SD, 57007

²Department of Chemistry, Biochemistry and Physics, South Dakota State University, Brookings, SD, 57007

Plant-based protein isolates (PIs) have multiple applications in food and biomanufacturing. Sunflower meal (SM) is a protein-rich substrate with huge potential for PI due to a balanced amino acid profile and low level of antinutritional factors. However, PIs from SM have poor yield, color, flavor and functional properties. High fiber, phenolic compounds and black coloration from hulls are the known contributing factors. Size-fractionation like air-classification is common in protein purification, which may be used to fractionate SM into fiber-rich and protein-rich fractions. Similarly, fungi can break down phenolics, fibers and proteins, subsequently improving yields and PI quality. Despite these benefits, substrates are not typically fermented before protein extraction due to detrimental impact of heat sterilization on PI yield and functional properties. Non-thermal sterilization methods like gamma irradiation can be an alternative to harness positive impacts of fermentation. So, this research focused on studying if size-fractionation and fungal fermentation of SM can improve PI yield and functional properties. Ground SM was sieved (0.075-1mm sieves) and each fraction was heat sterilized (121°C, 30 min) or gamma irradiated (10 KGy) followed by fermentation with Aspergillus oryzae (Ao) or Aspergillus niger (An). Proteins from each sample were extracted and analyzed for yield, protein content and phenolic content (TPC). Finer SM fractions had better yield and purity of PIs. PIs from HSSM had lower yield and purity against raw SM, whereas that from GISM had no significant impact on PI yield and purity. Upon fermentation, the protein purity and yield of PI decreased significantly regardless of the microbe used, indicating proteolytic activity of fungi. Although the yield remained constant, irradiated samples upon fermentation yielded PIs with significantly higher protein purity. For coarser SM fraction, Ao fermentation significantly reduced TPC values in autoclaved samples while both microbes significantly reduced TPC in irradiated finer SM fraction.

South Dakota State University
Dr. Bishnu Karki