Effects of ultrasonic treatment on protein extractability during complex processing of sunflower seeds

In this study sunflower seed cake produced on a screw press by cold pressing of dehulled sunflower seeds of confectionery-type sunflower was used as a raw material for obtaining of sunflower protein preparations. Ultrasonic treatment of the phenol-free cake was applied for improvement of extractability of proteins after the removal of phenolic compounds by treatment of dehulled sunflower press cake with an aqueous ethyl alcohol solution. Sonification was accomplished by the generator at ultrasound frequency of 22.00 ± 1.65 kНz with a duration of ultrasonic treatment from 5 to 15 minutes. Extraction of proteins was carried out in a mild alkaline medium with 0.1 % sodium bicarbonate solution with a hydro module of 1: 5 and temperature of 45 ± 2° C. Protein and dry matter content of protein extracts proportionally increased after 5-12 minutes of ultrasonic treatment with the formation of homogeneous protein extracts stable to solid phase separation and characterized by a lighter colour in comparison with the control sample not subjected to ultrasonic processing. However, after 15 minutes of ultrasonic treatment protein extracts lost uniformity with sedimentation of a solid fraction. Studies demonstrated that application of ultrasonic treatment prior protein extraction resulted in a growth of dry matter and crude protein content of sunflower protein extracts correspondently to the duration of sonification. This effect might be beneficial for an increase of protein yields in processes of manufacturing of light-coloured sunflower protein concentrates and isolates and for manufacturing of functional protein drinks from sunflower seeds. Additionally, it has been shown that sonication of sunflower protein solutions obtained after extraction of protein substances with 0.1 % NаНСО3 solution and removal of insoluble residue significantly improved their sedimentation stability and resulted in a lighter colour of resulted protein solutions in comparison with a conventional treatment by a high-speed disperser. Such treatment might be used in processes of manufacturing of dairy milk analogues from sunflower seeds.