Abstract:

The enzymatic hydrolysis of egg white albumin and changes in its structural properties were studied. As
evaluated in terms of degree of hydrolysis (DH), alkaline protease was determined as the best enzyme to hydrolyze egg
white albumin, which was significantly superior to other proteases tested, providing a DH value of 26.55% (P < 0.05). The
enzymatic hydrolysis process was studied through single factor and quadratic general rotary unitized design experiments.
The structural properties of egg white albumin and its hydrolysate were characterized by ultraviolet (UV), Fourier transform
infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The results showed that the optimum hydrolysis
conditions were as follows: hydrolysis temperature, 52.5 ℃; hydrolysis time, 5 h; pH, 8.25; enzyme dosage, 5 500 U/g;
and substrate concentration, 5%. Under these conditions, the maximum DH value of 27.88% was obtained. The resulting
hydrosulfuryl content showed a decrease of 3.6 mol/(L·g) in surface hydrosulfuryl, a significant increase in solubility, a
decrease of 18.18% in foaming ability, and a reduction of 20.24% in foam stability as compared to egg white albumin. Moreover,
the emulsifying index and emulsion stability of the hydrolysate increased by 13.56 m2/g and 10.46%, respectively. At the same
time, the enzymatic hydrolysis led to peptide chain cleavage of egg albumin, damage to the ordered secondary structure, exposure
of more amino acid residues, slight decrease in α-helix, and corresponding increases in β-turns and hydrophilic groups.

Key words: egg white ovalbumin (OVA), hydrolysate, structure characterization, functional property