Sustainable sunflower processing — II. Recovery of phenolic compounds as a by-product of sunflower protein extraction

A process for the recovery of polyphenol-rich extracts from the production of light colored sunflower protein isolates by combining mild-acidic protein extraction with adsorptive removal of phenolic compounds has been developed. In preliminary trials, different solvents were examined to evaluate their suitability for an exhaustive desorption of the polyphenols from a food-grade adsorbent resin. For this purpose, the elution behavior of different solvent–water mixtures was assessed at identical temperatures and flow rates. Besides methanol and ethanol, 2-propanol showed the most promising results. Furthermore, a D-optimal experimental design was applied to further optimize desorption of phenolic compounds from the adsorbent resin. Optimal conditions were deduced from experiments performed at different temperatures and flow rates and with varying solvent concentrations also evaluating the phenolic compound profiles at each step of the recovery process. Finally, antioxidant capacity of the polyphenol-enriched eluates was determined using the Folin–Ciocalteu and FRAP (ferric ion reducing antioxidant power) assays with ascorbic acid and trolox, respectively, as reference compounds.Industrial relevanceProtection against oxidation is a major challenge for the retention of sensory quality of processed foods. Since consumers generally reject artificial food additives, their substitution by natural counterparts is of increasing relevance. Phenolic compounds of different plant sources such as grape and apple pomace are known as potent antioxidants and radical scavengers. Consequently, to achieve sustainability of sunflower processing and complete utilization of by-products arising from sunflower oil production, polyphenols co-extracted during sunflower protein recovery from the expeller were recovered by adsorption technology. After their exhaustive desorption from the adsorber resin, the polyphenol enriched eluate may be used as a natural antioxidant due to its high antioxidant activity as demonstrated by this study.

► Sunflower polyphenols were recovered by resin adsorption and optimized desorption. ► 2-Propanol revealed best desorption properties. ► Desorption process parameters were optimized using a D-optimal design. ► Up to 99% of the adsorbed polyphenols were recovered upon elution. ► Fractions with high phenolic contents and antioxidant potential were obtained,