Effect of High Pressure Treatment on Rheological Characteristics of Egg Components

Abstract

The objective of this study was to evaluate the effect of high pressure treatment on rheological properties of various egg components (i.e., egg white, egg yolk, and whole liquid egg). A five-level central composite design with three independent variables (pressure, 281.8–618.2 MPa; temperature, 8.2–41.8°C; pressure holding time, 1.6–18.4 min) was employed. Samples were packed in plastic pouches, heat sealed, and subjected to pressure treatment in an isostatic press. Shear and time-dependent rheological properties were evaluated using a 3-segment (each 5 min) program with the shear rate initially increasing from zero to 100 s⁻¹ (upward curve), then held at 100 s⁻¹ (hold curve), and finally decreasing from 100 to 0 s⁻¹ (downward curve) using a parallel plate rheometer. Power law model was fitted to the upward (virgin) and downward curves while Weltman time dependency model was fitted for the hold curve (R² > 0.90). Rheological properties were most significantly affected by pressure followed by holding time and temperature for all egg components. In general, they showed thixotropic shear thinning behavior and reduction in time dependency, which was dependent on the level of processing treatment used (combination of pressure, time, and temperature level). The high pressure treatment resulted in a progressive transition of egg components from flowable liquid-like behavior (218–350 MPa) to semi-viscous (350–500 MPa) to highly-viscous (500–618 MPa) behavior. Rheology-based optimal conditions satisfying HP pasteurization needs were identified.

Keywords:

• High pressure processing
• Rheology
• Central composite rotatable design (CCRD)
• Power law
• Egg components