Production of egg white hydrolysate by digestion with pineapple bromelain: optimization, evaluation and antioxidant activity study

Abstract

Chicken egg white is known to be an excellent source of good quality proteins to make hydrolysate with potential bioactive properties. Enzymatic digestion is a well-known method to produce protein hydrolysates; however, the type of enzyme determines the bioactive potential of the protein hydrolysates due to difference in their catalytic specificity. In this study, process optimization, production and evaluation of whole egg white protein hydrolysate (WEWPH) using pineapple bromelain through the Box-Behnken design were carried out. The design experiment (r ² = 0.9557) displayed a significant (p < 0.01) effect of pH of egg white (9.0), hydrolysis time (24 h), and enzyme/substrate ratio (3.2 unit/g substrate) on hydrolysis and to form bioactive WEWPH. Antioxidant activity of the WEWPH was confirmed by DPPH radical scavenging assay. Gel filtration chromatography, SDS-PAGE and FTIR spectroscopy analysis of WEWPH revealed the digestion of egg white and the integrity of WEWPH in terms of secondary structure. The WEWPH exhibited strong scavenging activities of DPPH (EC₅₀ = 238.3 µg/ml), ABTS ABTS (EC₅₀ = 54.9 µg/ml), peroxyl (EC₅₀ = 391.6 µg/ml) and superoxide radicals. The WEWPH also displayed reducing power and singlet oxygen quenching activity. These results reveal that the bioactive WEWPH could be a promising ingredient in health food and nutraceuticals.

Supplementary information: The online version contains supplementary material available at 10.1007/s13197-021-05188-0.

Keywords: Antioxidant activity; Bromelain; Chicken egg; Egg white hydrolysate; Pineapple crown.

Fig. 1

Time scale of bromelain digestion of whole egg white protein and production of antioxidant whole egg white protein hydrolysate (WEWPH) (a) and response surface plots of the model (b) used in Box-Behnken experimental design for the antioxidant WEWPH production. Different lowercase letters in the graph indicates values are significantly different from each other and the significance accepted at p < 0.05

Fig. 2

Pareto graph of significant variables (a) and characteristic of the model used in Box-Behnken experimental design (b) for the digestion of whole egg white protein by bromelain and production of antioxidant whole egg white protein hydrolysate

Fig. 3

SEM (a) of freeze dried whole egg white protein (A) and whole egg white protein hydrolysate (WEWPH) (B) and gel filtration chromatogram of WEWPH (b)

Fig. 4

SDS-PAGE pattern of non-hydrolyzed whole egg white protein (WEWP) (Lane 1), whole egg white protein hydrolysate (WEWPH) (Lane 2), standard protein Mw marker (Lane 3) (a) and ATR-FTIR spectrum of WEWPH (^_____ A) and WEWP (––– B) (b)

Fig. 5

Antioxidant activities of the extract of whole egg white protein hydrolysate. DPPH (a), ABTS (b), peroxyl (HO₂) (c) and superoxide anion (O₂⁻) (d) radicals scavenging activities (%); reducing power (e) and singlet oxygen (¹O₂) scavenging activity (f). Different lowercase letters in the graph indicates values are significantly different from each other and the significance accepted at p < 0.05