J. Biomedical Science and Engineering, 2009, 2, 617-620
doi: 10.4236/jbise.2009.28089 Published Online December 2009 (http://www.SciRP.org/journal/jbise/
JBiSE
).
Published Online December 2009 in SciRes. http://www.scirp.org/journal/jbise
Effects of ultra-high hydrostatic pressure on foaming and
physical-chemistry properties of egg white
Rui-Xiang Yang, Wen-Zhao Li, Chun-Qiu Zhu, Qiang Zhang
Key Laboratory of Food Nutrition and Safety, Tianjin University of Science & Technology, Tianjin, China.
Received 11 July 2009; revised 1 September 2009; accepted 2 September 2009.
ABSTRACT
The influences of ultra-high hydrostatic pressure treat-
ment on foaming and physical properties (solubility,
hydrophobicity and sulfhydryl content) of egg white
were investigated. A pressure range of 0-500 MPa, time
range of 0-20 min and pH range of 7.5-8.5 were se-
lected. The foaming property of egg white is improved
by 350Mpa and 10min. The treatment resulted in in-
crease of sulfhydryl content of egg white, while solu-
bility and hydrophobicity were significantly decreased.
Keywords: Ultra-High Hydrostatic Pressure; Egg White;
Foaming Property
1. INTRODUCTION
Egg white is well known for their high nutritional quality,
foaming, gelling and emulsifying characteristics, which
can give the foods unique color, flavor, and texture char-
acteristics. Therefore, as an important ingredient, egg white
has been wildly applied in the food industry, such as
cakes, biscuits, breads, ice cream, and other protein
products [1]. At present, for convenience and safety,
liquid egg white products are widely used by home and
producer. However, decrease of the foaming property
after pasteurization is found in practice, which seriously
affects the application and development of the egg white
products.
Ultra-high static pressure technology is a new sterili-
zation technology, which can be used to resolve the
problems brought by pasteurization. Ultra-high pressure
can improve the function of biological macromolecules
by modifying their structure [2]. The high pressure does
not affect the primary structure of protein molecules, but
can cause agglutination of protein by changing the hy-
drogen bonds, disulfide bonds and hydrophobic groups
among the protein molecules. In addition, ultra-high hy-
drostatic pressure can cause viscosity and surface ten-
sion of egg white increased [3]. The relationship be-
tween foaming property and solubility, hydrophobicity,
sulfhydryl content under ultra-high hydrostatic pressure
is also investigated in this paper, and only the irreversible
changes in the properties are taken into account.
2. MATERIALS AND METHODS
2.1. Materials and Equipments
Fresh eggs were obtained from supermarket. Eggshell was
washed by clean water and exposed to ultraviolet light
for 30 min to disinfect. The egg white was separated
from egg yolk and the chalazae were removed. The al-
bumin was gently mixed and stored at 4 until use. ℃
The protein content of the egg white was determined to
be 11.23 ± 0.56 % (w/v).
2.2. Ultra-High Hydrostatic Pressure Treatment
A volume of 200 mL of egg white was packed in poly-
ethylene plastic packs (170×120mm) and sealed. The ultra-
high hydrostatic pressure treatment was performed in
high pressure equipment (Hpp-M1, Senmiao, China) and
a pressure range of 0-600 MPa, time range of 0-20 min
were selected in the experiment. All samples were ana-
lyzed at room temperature after 24-hour storage at 4.℃
2.3. Determination of Foaming Property
A volume of 35 mL (18～25) egg white was placed in ℃
a graduated cylinder of 250 mL (diameter =398 mm) and
whipped for 5 min (which is an optimal time for whip-
ping egg white in this measurement system in previous
study) with a rotating anchor (275 mm diameter, rotor
from the bottom of the graduated cylinder 15 mm) at
2100 rpm, using a laboratory stirrer with controlled con-
stant speed (OJ-100, Onuo, China). The volume of foam
(V0) was recorded immediately after the whipping
stopped. The foaming capacity (FC) [4] was defined by
%(%) 100
35
0 V
FC (1)
The volume of drainage of liquid (Vd) was recorded at
10 min, The foam stability was defined by

618 R. X. Yang et al. / J. Biomedical Science and Engineering 2 (2009) 617-620
SciRes Copyright © 2009 JBiSE
0
(%) 100%
d
V
Drainage V  (2)
Samples were determined in triplicate.
2.4. Determination of Solubility
Samples were centrifuged during 10 min at 10,000 r/min
and 18. Protein content of th℃e supernatant was deter-
mined.
2.5. Determination of Sulfhydryl Content
The concentration on sulfhydryl (SH) groups of the egg
white solutions was determined using Ellman’s reagent
(5′, 5-dithiobis (2-nitrobenzoic acid), DTN-B). 1mL of
sample add to 4mL of 0.05mL 0.01M DTNB in phos-
phate buffer (0.1M, pH 8.0), after 20min of mixing, the
reaction mixture was centrifuged during 15 min at
10,000 r/min to remove precipitated protein. Finally, the
absorbance of the supernatant was measured at 412 nm
against a reagent blank. A blank sample in which DTNB
was substituted by phosphate-buffer was carried through
in parallel. The sulfhydryl content is expressed as a mole
thiol/globulin grams = n mol / mg protein [5].
2.6. Determination of Surface Hydrop-Hobicity
The determination of the protein hydrophobic domains
through Takagi [4] approach, using 8-aniline-based-1-
Chennai acid (referred to as ANS). Each sample was
diluted with the 0.1M phosphate buffer (pH6.8), until the
protein concentration of 0.05%, 4.5mL of the diluted
sample and 0.5mL 1.25×l0-3m ANS mixed phosphate
buffer. Placing at room temperature for two hours, the
fluoresceence intensity was measured (excitation wave-
length 375nm, Kaloula 1.0nm, emission wavelength of
420-600nm (475nm), Kaloula 1.0nm, medium-speed
scanning speed). Globulin in the hydrophobic region is
expressed as fluorescence intensity and protein concen-
tration of 0.05%.
3. RESULTS AND DISCUSSIONS
3.1. Effect of High Hydrostatic Pressure on
Foaming C Property of Egg White
Foaming property is one of the most important surface
characteristic of protein molecule. Albumin proteins are
typical amphiphilic molecules, which are easy to extend
on the water-air interface and adsorb gas in the whipping
process. It has been verified that globulin and albumin of
egg white play a major role in forming bubble; Ovomu-
cin and egg lysozyme are favorable for foaming stability
[1]. Iesel Plancken has shown that the foaming property
of egg white is mainly relative to the content of sulfhy-
dryl and the flexibility of protein molecule. The interac-
tion between protein and protein can improve the foam-
ing stability of egg white [2].
0
50
100
150
200
250
0100 200300 400 500
p/MPa
FC(%)
0
5
10
15
20
25
30
35
Drainage(%)
FC Drainage
Figure 1. Effect of pressure on foaming property of
egg white pH =8.1, t = 10 min, 18℃.
There are not significant changes for FC between
0-200MPa, as can be seen in Figure 1. But the drainage is
increasing and reaches the maximum at 200MPa, which
means the worst foam stability. With the pressure increas-
ing, the FC is still rising until 350 MPa, but the drainage
has been decreasing and reaches the minimum at 350
MPa. According to the relevant literature, the phenome-
non above was analyzed as follows. It is known that
practical aggregation of proteins can raise the protein
foaming capability and stability [4]. In this process, ag-
gregation affection can enhance the reaction among pro-
teins and make them become precipitate or gel. While
the protein gel appears, the foaming capability and sta-
bility will decline sharply.
3.2. Effect of Time on Foaming Property of Egg
White
As can see from Figure 2, with the extension of proc-
essing time, the foaming capability increases and reaches
the maximum at 10 min. While the drainage drops to the
lowest, there is the best foaming stability. It indicates
that in the aggregation of protein process, 10 min is
suitable for foaming characteristic of egg white. Ac-
cording to the relevant report, the β-sheet structures of
0
50
100
150
200
250
0510 1520 25
t/min
FC(%)
0
5
10
15
20
25
30
35
40
Drainage(%)
FC Drainage
Figure 2. Effect of time on foaming property of egg
white p = 350 MPa, pH = 8.2, 18.℃

R. X. Yang et al. / J. Biomedical Science and Engineering 2 (2009) 617-620 619
SciRes Copyright © 2009 JBiSE
protein treated with the pressure are unfolded, which can
improve the ability of maintaining gas for egg white and
make it easy to form bubble [4]. And also, it has en-
hanced the interaction among proteins, which is favor-
able for foaming stability. After 10min, the protein pre-
cipitate starts to appear, and the foaming capability is
decreasing. The previous studies have shown that when
egg white is treated by 350Mpa for 10min, the surface
tension and viscosity is increasing [3]. From the phe-
nomenon and the relevant conclusion above, we can
draw a conclusion as follows: ultra-high pressure treat-
ment can change the structure of protein molecules and
cause aggregation of proteins, which can improve the
foaming property of egg white.
Next, 10min was selected for different ultra-high
pressure treatment to investigate the relationships be-
tween foaming property and other characteristic of egg
white.
3.3 Effect of High Hydrostatic Pressure on
Solubility of Egg White
Protein solubility is an important property of hydration.
The protein and water molecules are connected through
the interaction of the peptide bond or amino acid side
chain (ionization, polar or non-polar group) [1]. As can
be seen from Figure 3, the solubility of protein de-
creases with the pressure increasing. The tertiary and
quaternary structures of protein treated by the ultra-high
pressure were destroyed for that molecules of protein
have been unfolded [4]. The reactions of aggregation
among protein molecules have been enhanced, therefore,
the solubility of egg white becomes decreasing. Com-
paring to Figures 1,3, there are not significant linear
correlation between the foaming properties and solubil-
ity of egg white treated by ultra-high pressure. When the
percent of soluble protein is 71%, the foaming property
of egg white is better.
3.4. Effect of High Hydrostatic Pressure on
Surface Sulfhydryl Content of Egg White
As can been seen from Figure 4, there are significant
changes of surface sulfhydryl content with pressure
0
20
40
60
80
100
0100 200250 300 350400
p(Mpa)
solubility(%)
Figure 3. Effect of pressure on solubility of egg
white pH =8.1, t = 10 min, 18℃.
reaching the maximum at 350MPa. When the egg white
is treated by ultra-high hydrostatic pressure, the structure
of the ovalbumin has been changed, which causes four
internal sulfhydryl of c molecule being exposed and in
creases the surface sulfhydryl content on the bases of
relevant literature. Comparing with Figures 1,5, there is
the same trend between the foaming properties and the
surface sulfhydryl content of egg white. The foaming
capability, stability and surface sulfhydryl content all
reach the maximum at 350 Mpa.
3.5. Effect of High Hydrostatic Pressure on
Hydrophobicity of Egg White
As can been seen from Figure 5, the hydrophobic of egg
white has the maximum at 100MPa. With the pressure
increasing, hydrophobicity of egg white decreases. It is
known that hydrophobic interaction is the main force to
maintain protein tertiary structure. So we can deduce
that the tertiary and quarternary structures of proteins of
egg white treated by the ultra-high hydrostatic pressure
are destroyed, and more hydrophobic regions are ex-
posed. With the pressure increasing, hydrophobic amino
acids are buried and the hydrophobic region is reduced.
Therefore, hydro-phobic property of protein decreased.
4. CONCLUSIONS
The foaming capability and stability of egg white are im-
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0100 200 250300 350400
p(Mpa)
exposed SH (OD)
Figure 4. Effect of high hydrostatic pressure on sulfhy-
dryl content of egg white pH =8.1, t = 10 min, 18℃.
23
23.5
24
24.5
25
25.5
26
26.5
27
27.5
0100 200 250 300 350 400
p/MPa
OD
Figure 5. Effect of high hydrostatic pressure on hydro-
phobicity of egg white pH =8.1, t = 10 min, 18℃.

620 R. X. Yang et al. / J. Biomedical Science and Engineering 2 (2009) 617-620
SciRes Copyright © 2009
proved by the ultra-high hydrostatic pressure (100-400
MPa), and play the best performance by 350Mpa and
10min. The findings of the experiment of physical prop-
erties of egg white with ultra-high hydrostatic pressure
show that with increasing pressure, the solubility of egg
white will decrease. There is positive relation between
the surface sulfhydryl content and the foaming proper-
ties of egg white. When the hydrophobicity of egg white
is the lowest, the foaming capacity and foam stability of
egg white will reach the best performance.
JBiSE
5. ACKNOWLEDGEMENTS
This research is support by the research fund of personnel of Tianjin
University of Science & Technology.
REFERENCES
[1] X. D. Li and L. W. Zhang. (2005) Egg Science and
Technology. Chemical Industry Press.
[2] E. V. Plancken, A. VanLoey, and M. E. Hendricks. (2007)
Foaming properties of egg white affected by heat or high
pressure treatment, Journal of Food Engineering, 78,
1410–1426.
[3] W. Wang and W. Z. Li. (2009) Effect of ultra-high hydro-
static pressure on foaming and physical properties of the
egg white. Journal of Tianjin University of Science and
Technology, 24, 35–38.
[4] H. Wang and Z. C. Tu. (2008) Egg white protein dynamic
modification of ultrahigh-pressure micro jet and mecha-
nism of, Nanchang University.
[5] K. Lomakina. (2005) A study of the factors affecting the
foaming properties of egg white-a review. Food Science,
24, 110–118.
[6] J. Liu and B. Jiang. (2007) Effects of ultra-high pressure
on foaming property of chickpea protein isolated. Anhui
Agricultural Science, 35, 9012–9013.