Effects of pH, temperature and pulsed electric fields on the turbidity and protein aggregation of ovomucin-depleted egg white

- Ovomucin-depleted egg white (OdEW) was prepared by isoelectric precipitation.
- Pulsed electric fields processing caused pH-dependent protein aggregation.
- Proteins in OdEW solution were most susceptible to aggregation at pH 5.
- Protein stability is different under pulsed electric fields and thermal processing.
- PEF processed OdEW has potential added to products such as protein fortified drinks.

The effect of either pulsed electric fields (PEF) or thermal processing on protein aggregation of ovomucin-depleted egg white (OdEW) solutions at different pH was assessed by solution turbidity and SDS-PAGE. Heating to 60 °C for 10 min caused marked protein aggregation of OdEW at pH 5, 7, and 9. At constant electric field strength (E = 1.4-1.8 kV/cm), PEF processing under high specific energy input (Wspec = 260-700 kJ/kg) induced some protein aggregation at pH 5 and 7, but not at either pH 4 or 9. Similar effects of pH on protein aggregation were observed upon PEF processing at varied E (from 0.7 to 1.7 kV/cm) but with constant Wspec (713 kJ/kg). Analysis by SDS-PAGE revealed that proteins in the OdEW solution at pH 5 were most susceptible to both PEF- and heat-induced protein aggregation and lysozyme was only involved in the formation of insoluble aggregates under PEF. The present study shows that PEF treatment has considerable potential for minimizing protein aggregation in the processing of heat-labile egg white proteins. Retaining the OdEW proteins in solution during processing has potential industry application, for example, protein fortification of drinks with OdEW, where minimizing solution turbidity would be advantageous.

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