Structural and functional characterization of papain-assisted ultrasound pretreated egg white hydrolysis

Abstract

The main objective of this research is to quantitatively investigate the impact of high intensity ultrasound waves generated by probe-type sonicator on the selected functional and structural properties of papainassisted egg white protein hydolysis (PEWPHs). As well, the effect of pretreatment time on the susceptibility to proteolysis was investigated. 10 % (w/w) aqueous solution of egg white proteins (EWPs) was sonicated at an actual ultrasonic power of 30.7 W. The trials have been accomplished using the modified vibratory cavitation test set up source at resonant frequency of 20 ± 0.2 kHz during the different pretreatment time (2, 5, 10, 15 and 20 minutes). The functional properties of the PEWPHs were probed in terms of solubility, digestibility and foaming ability. In order to understand the molecular structure and morphology of ultrasound pretreated EWPs, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy (SEM) were employed to image the materials. The performance of ultrasound PEWPHs were compared to their untreated counterparts. The proteolytic pattern of papain-assisted EWP hydrolysis was significantly improved for all pretreatment time applied, but the prolonged exposure to ultrasound of 20 min seemed to have a negative effect on the EWPs hydrolysis. The treatment of the EWPs during 5 min can be adopted as the optimal for PEWPHs. Ultrasound pretreatment seemed to increase solubility and digestibility and also caused enhanced foaming properties of PEWPHs compared to the control (untreated EWPs). It was found that particle morphology (SEM images) of PEWPHs were completely different and the less small particles were trapped in large dents of large particles and narrow range of particle size was observed for ultrasound pretreated PEWPHs. SDS-PAGE patterns affected on the release some small peptides (< 14.4 kDa) causing a significant decrease in molecular weight of ultrasound pretreated PEWPHs. The outcomes presented here suggest that the application of the probe-type sonicator have na important role in the improvement of functional and structural properties of PEWPHs and the combined ultrasound pretreatment and enzymatic hydrolysis, not only represents a rapid, efficient and reliable alternative to improve the quality of EWPs, but it also has the potential to develop new products with a unique functionality.