Impact of Ultra-High Pressure Homogenization on the Structural Properties of Egg Yolk Granule

Abstract

Ultra-high pressure homogenization (UHPH) is a promising method for destabilizing and potentially improving the techno-functionality of the egg yolk granule. This study's objectives were to determine the impact of pressure level (50, 175 and 300 MPa) and number of passes (1 and 4) on the physico-chemical and structural properties of egg yolk granule and its subsequent fractions. UHPH induced restructuration of the granule through the formation of a large protein network, without impacting the proximate composition and protein profile in a single pass of up to 300 MPa. In addition, UHPH reduced the particle size distribution up to 175 MPa, to eventually form larger particles through enhanced protein-protein interactions at 300 MPa. Phosvitin, apovitellenin and apolipoprotein-B were specifically involved in these interactions. Overall, egg yolk granule remains highly stable during UHPH treatment. However, more investigations are needed to characterize the resulting protein network and to evaluate the techno-functional properties of UHPH-treated granule.

Keywords: egg yolk granule; microstructure; protein aggregation; proteins; ultra-high pressure homogenization.

Figure 1

Experimental design of the production of the different fractions from egg yolk granule after ultra-high-pressure homogenization treatments. G1c: initial control granule, G1p: initial pressure-treated granule, G2p: granule from initial pressure-treated granule, P2p: plasma from initial pressure-treated granule, G2c: control granule from initial control granule, P2c: control plasma from initial control granule.

Figure 2

Particle size distribution of initial (G1c) and pressure-treated granule (G1p) at 50, 175 and 300 MPa with 1 and 4 passes (A), and factorial effect of pressure level (50, 175 and 300 MPa) and number of passes (1—blue and 4—green) on the two populations (1—hatched and 2—filled) (B). Different letters, a–c for population 1 and A–C for population 2, indicate significant differences (p < 0.05) due to interaction between pressure and passes and solely due to the pressure level (Tukey test, α = 0.05, n = 3).

Figure 3

Impact of pressure level (50, 175 and 300 MPa) and number of passes (1—blue and 4—green) on the mean diameter expressed as volume (D_[4,3]) of pressure-treated granule (G1p). Data with different letters (a-b) and * are significantly different (p < 0.05), due to a simple effect of pressure and passes (Tukey test, α = 0.05, n = 3).

Figure 4

Microstructures of (A) initial control granule (G1c) and pressure-treated granule (G1p), (B) control granule from initial control granule (G2c) and granule from pressure-treated granule (G2p), and (C) control plasma from initial control granule (P2c) and plasma from pressure-treated granule (P2p) observed by transmission electron microscopy with a magnification of 3K.

Figure 5

Native (A,C,E) and reduced (B,D,F) SDS PAGE of initial granule (G1c) and pressure-treated granule (G1p) (A,B); control granule from initial granule (G2c) and granule from pressure-treated granule (G2p) (C,D); and control plasma from initial granule (P2c) and plasma from pressure-treated granule (P2p) (E,F).