Effect of Size Fractionation and Dephenolization of Sunflower Meal on the Functional Properties and Digestibility of Sunflower Protein Isolates

Justification: Sunflower meal (SM) is a byproduct of sunflower oil processing industry. It has gained significant attention as a promising plant protein source because of its high protein and relatively low antinutrients content. But the presence of high fiber and chlorogenic acid in meal has detrimental effects on the yield, digestibility, sensory and functional properties of protein isolate. Although solvent extraction is the most popular technique for dephenolization, it has negative impacts on protein functionality and has solvent toxicity and flammability problems. Alternatively, supercritical fluid extraction (SFE) can be a promising alternative for phenolics extraction. Also, size-fractionation has been used previously for protein concentration without any impact on protein quality. Therefore, the objective of this research is to study the effect of dephenolization with SFE and size-fractionation of SM on the functional properties of sunflower protein isolate (SPI).
Methods: Ground SM was dephenolized using SFE (ethanol modified supercritical CO₂ as solvent) and further fractionated using different sieves (1 mm, 0.5 mm, 0.25 mm and 0.125 mm). Protein was isolated from each fraction by solubilization at pH 10.5 followed by precipitation at pH 4.5. The isolates were freeze dried and analyzed for yield, in-vitro protein digestibility, solubility, emulsification, foaming and gelation properties, water binding capacity, wettability and color measurement.
Results: Raw SM was found to have 13% moisture, 38.99% crude protein (CP), 27.85% crude fiber (CF) and 0.32% crude fat. Upon size-fractionation, >1 mm fraction had the highest CF (55.06%) and the least CP (11.54%) while 0.125-0.25 mm fraction had the highest CP (47.47%) and the least CF (14.4%). The analysis of functional properties of protein isolates is currently in progress. Significance: This study suggested that dephenolization with SFE and a simple size-fractionation of SM prior to protein extraction can improve the yield, digestibility, sensory and functional properties of SPI produced.