Antioxidant activity improvement of identified pine nut peptides by pulsed electric field (PEF) and the mechanism exploration

- Four pine nut peptides were identified from pine nut protein hydrolysate.
- DPPH radical inhibition of KCHQP were improved by PEF technology.
- The structure of PEF-treated KCHQP was not changed.
- Zeta potential of PEF-treated KCHQP was reduced.

This study was aimed to explore the mechanism of peptides antioxidant activity improvement treated by pulsed electric field (PEF). The pine nut (Pinus koraiensis Sieb. et Zucc) peptides were used as the experimental materials. DPPH radical inhibition and cellular antioxidant activity (CAA) were applied to evaluate the peptides antioxidant activity. Structures of PEF-treated peptides were analyzed by mid-infrared (MIR) and circular dichroism (CD) spectroscopy. Peptides were indentified including Gln-Cys-His-Lys-Pro, Gln-Cys-His-Gln-Pro, Lys-Cys-His-Gln-Pro(KCHQP), and Lys-Cys-His-Lys-Pro. KCHQP was with the strongest DPPH radical scavenging of 89.10% ± 0.20%, and CAA units of 78.40 ± 1.71. Moreover, the DPPH radical scavenging of KCHQP was significantly increased from 89.10% ± 0.20% to 93.22% ± 0.09% under the PEF treatment conditions (pulse frequency 1800 Hz, and electric field intensity 15 kV/cm). The MIR and CD spectroscopy indicated that the structure of KCHQP was not changed by PEF. However, the zeta potential was reduced from 11.6 ± 0.28 mV to 0.4 ± 0.06 mV. This study enriched the resource of antioxidant peptides with indentified amino acid sequence. It provided a way to investigate mechanism of peptides antioxidant activity improvement treated by PEF.