Sustainable sunflower processing — I. Development of a process for the adsorptive decolorization of sunflower [Helianthus annuus L.] protein extracts

A novel process for the production of light-colored sunflower protein isolates was developed, combining mild-acidic protein extraction with adsorptive removal of phenolic compounds. Four commercial food-grade adsorbent and three ion exchange resins were tested with regard to their affinity towards polyphenols. Amberlite™ XAD 16HP and FPX 66 showed optimal decolorization of the sunflower crude extracts. In contrast, ion exchange resins exerted maximal binding of monomeric phenolic compounds, but were less effective in removing colored compounds. Adsorption behavior of individual resins was assessed by adding resin to protein extracts varying the amounts of resin, protein concentration of the solutions and temperature. Furthermore, a D-optimal experimental design was applied to optimize adsorptive polyphenol removal from sunflower protein extracts using a styrene–divinylbenzene copolymer. Adsorption isotherms were determined for 5-O-caffeoylquinic acid and total phenolics, respectively. Optimal conditions were deduced from experiments at different temperatures, with different flow rates and extract concentrations. Finally, adsorbent and ion exchange resin columns were connected in series and successfully applied to produce light-colored sunflower protein on a pilot scale under the conditions optimized in laboratory experiments, thus demonstrating that this technology can easily be integrated into existing process lines.

Industrial relevance

A vital necessity to exploit novel protein sources arises from the increasing demand for human nutrition. Residues originating from sunflower oil production are rich in proteins and might serve as a source of plant proteins, which has not been valorized so far. This is due to their high contents of phenolic compounds that may interfere with the proteins lowering their nutritional value and impairing their sensory properties. Therefore, a process for mild-acidic protein extraction combining adsorption and ion exchanger technology for the removal of polyphenols from crude sunflower extracts was developed in the present study.