title: Physical and structural changes in liquid whole egg treated with high-intensity pulsed electric fields.
abstract: Liquid whole egg (LWE) is currently pasteurized through the application of heat; however, this treatment entails deleterious effects against some of the functional and technological properties of the product. In this study, the effect of high-intensity pulsed electric fields (HIPEF) processing (field strength: 19, 32, and 37 kV/cm) was compared to the traditional heat pasteurization (66 °C for 4.5 min). Different physical and structural characteristics of LWE, subjected or not to homogenization, were evaluated and compared, having the untreated LWE as a reference. Thermal treatment caused an increase in the viscosity of LWE, especially in nonhomogenized samples. HIPEF treatments did not modify the original color of LWE, whereas thermally treated samples developed an opaque appearance. LWE treated at 19 and 32 kV/cm exhibited a similar foaming capacity as fresh untreated egg, whereas thermal processing and PEF treatments of 37 kV/cm caused a substantial decrease in the foaming capacity of untreated liquid egg. Regarding the microstructure, the lipoprotein matrix appeared to be less affected by the HIPEF than by heat treatment if compared to the control. In addition, heat pasteurization had a significant impact on both the water-soluble protein content of the LWE samples (19.5% to 23.6% decrease) and the mechanical properties of the egg gels (up to 21.3% and 14.5% increase in hardness and cohesiveness, respectively). On the other hand, these parameters were not substantially affected in the HIPEF-treated samples. Heat-induced gels obtained from HIPEF-treated samples did not exhibit remarkable differences in the water-holding capacity (WHC) with respect to heat-pasteurized samples.
  
  
  CONCLUSIONS
  The impact of high-intensity pulsed electric fields (HIPEF) processing on technological properties of liquid-whole egg was investigated and compared to that of thermal processing. Heat treatments cause a severe impact on the foaming capacity, the water-soluble protein content, and the rheological properties of liquid egg samples, whereas HIPEF treatments better preserved the food matrix structure. Microscopic observations support these results, thus suggesting that HIPEF-processing has potential application for the preservation of liquid egg through nonthermal means.
authors.affiliation: Dept of Food Technology, Univ of Lleida, Rovira Roure 191, 25198 Lleida, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Marco-Molés
authors.forename: María A
authors.initials: MA
authors.lastname: Rojas-Graü
authors.forename: Isabel
authors.initials: I
authors.lastname: Hernando
authors.forename: Isabel
authors.initials: I
authors.lastname: Pérez-Munuera
authors.forename: Robert
authors.initials: R
authors.lastname: Soliva-Fortuny
authors.forename: Olga
authors.initials: O
authors.lastname: Martín-Belloso
mesh_terms: D055598:Chemical Phenomena; D003116:Color; D004531:Eggs; D004560:Electricity; D005511:Food Handling / Q000379:methods*; D005519:Food Preservation / Q000379:methods*; D006358:Hot Temperature; D008855:Microscopy, Electron, Scanning; D014783:Viscosity