Extracting egg yolk lecithin using PEF-assisted organic solvent

High-voltage pulsed electric field (PEF) is an emerging non-thermal processing technology that has recently generated much interest for improving the extraction rate of some bioactive substances and enhancing the quality of food products. To improve the extraction rate of egg yolk phosphatidylcholine (PC), PEF-assisted organic solvent was studied in this paper. Field strength (E), number of pulses (C) and moisture content of extraction solvent were chosen as three important factors affecting PC extraction. The extraction rate was determined using HPLC by the value of chromatographic peak area of PC which was proportional to PC content in the sample solution. Process conditions were optimized by the Box-Behnken experimental design. The results showed that the optimized operating parameters were as follows: field intensity 39 kV/cm, number of pulses 31, moisture content of extraction solvent 9% and PC content with optimized PEF treatment was 0.216 mg/mL. However, it was not higher than 0.196 mg/mL than the content of PC extracted by organic solvent without PEF treatment. The extraction rate of PC with PEF treatment was 10.2% higher than the one untreated. The value of a temperature rise of material liquid (ΔTs) increased with the increase in field strength and the number of pulses. In the experimental conditions tested (E: 10-50 kV/cm, C: 0-40, pulse width: 2 µs), ΔTs changed in the range of 0 to 8.4℃ at room temperature. The content of PC extracted by organic solvent without PEF treatment was 0.192± 0.001 mg/mL in this temperature range. The results indicated that PEF treatment had no significant effect on the temperature rise of material liquid, and the effect of ΔTs on PC extraction was much smaller than the field strength and pulse number. The changes of the PC molecular structure were analyzed by mid-infrared spectroscopy (FTIR). By a comparison of FTIR spectra of PC before and after PEF treatment, it showed that PEF-induced strong ionization destroyed a small number of P=O bonds (1 234 cm-1) and C=O bonds (1 734 cm-1), and the stretching vibrations of N—H and O—H (3 200 cm-1-3 500 cm-1) were weakened to a lesser extent. The results demonstrated that PEF treatment did not induce any significant change to the molecular structure of PC, which confirmed PEF, less damaging to food nutrients, is a kind of mild processing mode.