Ultrasound pretreatment of sunflower protein: Impact on enzymolysis, ACE-inhibition activity, and structure characterization

Abstract

Impacts of dual-frequency ultrasonic (DFU) with various operating modes (simultaneous and sequential modes) on degree of hydrolysis (DH) and conversion rate (CR) of sunflower meal protein (SMP) and activity of ACE-inhibition of SMP hydrolysates were examined. Results revealed that sequential and simultaneous modes enhanced DH by 7.73% and 11.22%, and CR by 26.23% and 26.98% of SMP (p < .05). Additionally, the maximal ACE-inhibition activity obtained at 75 min of enzymolysis was 64.46% for sonicated SMP hydrolysate (simultaneous mode), which was 32.52% higher than the control. Alterations in surface hydrophobicity, UV-Vis spectra, and intrinsic fluorescence indicated unfolding of SMP. AFM showed that sonication decreased the particles size and altered the structure of SMP. Amino acids composition demonstrated that both DFU modes pretreatments could improve the hydrophobic amino acids. Consequently, sonication enhanced DH, CR of SMP, and the activity of ACE-inhibition of hydrolysates confirmed by changes in SMP structure. Practical applications Sunflower protein, an extract from sunflower meal, is a potential source for preparing the bioactive compounds such as ACE- inhibition peptides. These peptides are safe, easy to absorb and stable, and have certain benefits for patients. Sonication with different operating frequency modes were applied to enhance enzymolysis of sunflower protein and ACE-inhibition activity of its hydrolysates. Sonication was displayed to be an operative technique to yield hydrolysates with good ACE-inhibition activity confirmed by monitoring the alterations in sunflower protein structure. Thus, sonication pretreatment of sunflower protein maybe practicable in the enzymolysis and the activity of ACE-inhibition in industry.