| Pulsed electric fields (PEF) is an emerging non-thermal processing technology used for thermosensitive materials stabilization and enzyme inactivation. Lactoferrin (LF) is an iron-binding glycoprotein present in external secretions such as milk, especially colostrums. LF has various bioactive functions such as broad-spectrum antimicrobial activity, promotion of iron transfer and absorption, immunomodulatory effects, et al. Therefore, it has great potential to be widely used in foods, pharmaceuticals, and cosmetics. There are little reports on the influence of PEF on bioactivity protein. In this paper, the influence of PEF on the structure and bioactivity (antibacterial activity and iron-binding capacity) of LF were studied. Optimal parameters were confirmed to protect the bioactivity of LF, which would be helpful to understand the biochemical effects of PEF treatment on other food ingredients.The structure of LF influenced by PEF was studied. The pH of LF solutions have no changes, but a little decreases of conductance under different electric fields strength and pulse amount. With electric fields strength increased to 35 kV/cm, circular dichroism spectroscopy measurements (CD) revealed that the structure proportionate ofα-helical decreased,β-structure enhanced, the molecular structure became more compactness and the molecular stability increased with increasing electricity fileds strength. It was shown by DSC that denaturation temperature enhanced and thermal stability increased of LF. And the Zeta potential was positive and a little decreased. But when the electric fields strength was to 40 kV/cm, the structure proportionate ofα-helical increased, the molecular structure loosen and the Zeta potential increased. When electric fields strength was to 30 kV/cm, and the pulse amount increased from 33 to 256, the structure proportionate ofα-helical and unfolded random structure was enhanced, molecule stability decreased.The changes of iron-binding capacity of LF was studied after PEF. When electric fields strength was to 30 kV/cm, and the pulse amount increased to 256, the relative iron-binding capacity enhanced apparently and was to 3.8 times compared with the control. The relative iron-binding capacity decreased 43% when electric fields strength was 35 kV/cm, and it enhanced to 87% at 40 kV/cm. But the treatment time and pulse width had negative effects on the iron-binding capacity. While pulse frequency, velocity of flow and shear effect had little influence on the iron-binding capacity of LF. When temperature increased from 35℃to 55℃, the relative iron-binding capacity of LF would come to the peak at 55℃, and it would decreased as the temperature continue to enhanced. The influence of PEF on structure and iron-binding capacity has similar changes.The antibacterial activity of LF affected by different PEF treatments. When electric fields strength less than 30 kV/cm, there was little changes in the activity of LF to inhibit E.coli and Staphy.aureus. But as electricity fields strength was to 35 kV/cm, the relative inhibit activity decreased to 76.6% and 82%, respectively. And the antibacterial activity had a little increase when the electric fields strength enhanced to 40 kV/cm. The antibacterial activity of LF enhanced as the pulse amount increased, the antibacterial activity became the highest when the pulse amount came to 256, and that would come down as pulse amount increased. Changes of pulse time and pulse frequency had little influence on the antibacterial activity of LF. As the increase of pulse width, the antibacterial activity of LF decreased. The antibacterial activity of LF would increase when the temperature enhanced, and when it came to a peak that would decrease as the temperature increased. Compared with the influence of PEF structure and iron-binding capacity, the influence of PEF on antibacterial activity has good consistency.
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