title: Effects of pH, temperature and pulsed electric fields on the turbidity and protein aggregation of ovomucin-depleted egg white.
abstract: 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 10min caused marked protein aggregation of OdEW at pH5, 7, and 9. At constant electric field strength (E=1.4-1.8kV/cm), PEF processing under high specific energy input (Wspec=260-700kJ/kg) induced some protein aggregation at pH5 and 7, but not at either pH4 or 9. Similar effects of pH on protein aggregation were observed upon PEF processing at varied E (from 0.7 to 1.7kV/cm) but with constant Wspec(713kJ/kg). Analysis by SDS-PAGE revealed that proteins in the OdEW solution at pH5 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.
authors.affiliation: Department of Food Science, University of Otago, Dunedin, New Zealand; Department of Biochemistry, University of Otago, Dunedin, New Zealand.
authors.forename: Ya-Fei
authors.initials: YF
authors.lastname: Liu
authors.affiliation: Department of Food Science, University of Otago, Dunedin, New Zealand. Electronic address: indrawati.oey@otago.ac.nz.
authors.forename: Indrawati
authors.initials: I
authors.lastname: Oey
authors.affiliation: Department of Food Science, University of Otago, Dunedin, New Zealand.
authors.forename: Phil
authors.initials: P
authors.lastname: Bremer
authors.affiliation: Department of Biochemistry, University of Otago, Dunedin, New Zealand.
authors.forename: Alan
authors.initials: A
authors.lastname: Carne
authors.affiliation: Department of Food Science, University of Otago, Dunedin, New Zealand.
authors.forename: Pat
authors.initials: P
authors.lastname: Silcock
mesh_terms: D003207:Conalbumin / Q000737:chemistry; D004529:Egg White / Q000737:chemistry*; D004560:Electricity; D004591:Electrophoresis, Polyacrylamide Gel; D005511:Food Handling / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D009113:Muramidase / Q000737:chemistry; D009391:Nephelometry and Turbidimetry; D010047:Ovalbumin / Q000737:chemistry; D010059:Ovomucin / Q000737:chemistry*; D066329:Protein Aggregates; D055550:Protein Stability; D012995:Solubility; D013696:Temperature; D000511:alpha-Macroglobulins / Q000737:chemistry
chemical_list: D066329:Protein Aggregates; D000511:alpha-Macroglobulins; D003207:Conalbumin; D010059:Ovomucin; C036828:ovomacroglobulin; D010047:Ovalbumin; D009113:Muramidase
keywords: Egg white protein; Protein aggregation; Pulsed electric fields; SDS-PAGE; Temperature; Turbidity; pH