Abstract:

Objective: To study the separation and stability of antioxidant peptides produced by enzymatic hydrolysis of
silkworm pupa protein with a commercial enzyme preparation. Methods: The antioxidant peptides derived from silkworm
pupa protein were separated and purified by ultrafiltration. Their antioxidant activity was determined by colorimetry.
Results: The antioxidant peptides with molecular weights of 200–3 000 D were obtained by ultrafiltration and their IC50 for
superoxide anion, hydroxyl, 1,1-diphenyl-2-picrylhydrazyl hydrate (DPPH) free radical were 18.85 mg/mL, 3.13 mg/mL,
and 35.23 μg/mL, respectively. The DPPH free radical scavenging rate of the antioxidant peptides after treatment with both
pepsin and trypsin for 4 h was increased from an initial level of 81.05% to 82.26%. The DPPH free radical scavenging rate
of the antioxidant peptides at a concentration of 100 μg/mL was 98.02% and 11.80% after treatment at pH 4 and 8 for 1 h,
and 87.11% after heat treatment at 95 ℃ for 1 h, respectively. The DPPH free radical scavenging rate at a concentration
of 60 μg/mL was reduced from an initial level of 51.58% to 22.68% after 6 h of incubation in the presence of 1.0 mol/L
NaCl. Conclusion: The 200–3 000 D antioxidant peptides generated by enzymatic hydrolysis of silkworm pupa protein were
capable of effectively scavenging superoxide anion and DPPH free radical and had reducing power; their DPPH free radical
scavenging activity in an acidic environment was higher than in an alkaline environment, and was effectively maintained by
desalination but not significantly affected by digestive enzymes or temperature.

Key words: enzymatic hydrolysis of silkworm pupa protein, antioxidant peptides, separation and purification, stability