1. Domínguez-Hernández Carolina del R.1, Salgado-Cervantes, Marco A.1, Beristáin, Cesar I.2, García, Hugo S.1, García-Alvarado, Miguel A.1
1Unidad de Investigación y Desarrollo de Alimentos, Instituto Tecnológico de Veracruz, Av. Miguel Ángel de Quevedo #2779, Veracruz, Veracruz, México.
2 Instituto de Ciencias básicas, Universidad Veracruzana, A.P. 575, Xalapa, Veracruz, México.
E-mail: karobsb@yahoo.com
PREPARATION OF NANO-EMULSIONS BY HIGH AND LOW ENERGY
METHODS
Nano-emulsions are emulsions with very small and
uniform particle size, usually in the range of 20-200 nm
(Gutiérrez et al., 2008, Jafari et al., 2006). This size
allows them to have high kinetic stability and a
transparent or translucent appearance, and can be
easily incorporated into beverages and food gels
without compromising their visual aspect (Tadros et
al., 2004). These systems are thermodynamically
unstable and require a rather large energy input for
their preparation. This energy input may come from
external sources of energy (high pressure
homogenizers, microfluidizers, ultrasound, high shear
mixers, etc.) or internal (chemical energy of the
system) (Sonneville-Aubrun et al., 2004). Methods that
use external power are called high-energy or
dispersion methods, while methods that use chemical
energy stored in the system are low energy or
condensation methods. Different studies have
evaluated high-energy methods employed for nano-
emulsion formulation (Abismaïl et al., 1999; Jafari et
al., 2006) observing more stable, less polydispersed
and smaller emulsion particle size using a probe-type
sonicator compared to emulsions prepared by
mechanical agitation under the same conditions
(Abismaïl et al., 1999). It has been proposed that high-
energy methods can produce nano-emulsions. Studies
evaluating a low energy method for nano-emulsions
formulation, which consisted of successive additions
of water to O/S mixture; assessed changing
composition at constant temperature (Sarduní et al.,
2005), observed that nano-emulsions formation is
dependent on the order addition of phases and showed
high kinetic stability (Sarduní et al., 2005). They are
being studied as controlled release vehicles for active
compounds (Acosta, 2009). The objective of this work
is to design and prepare nano-structured emulsions
using different high and low energy processes.
EMULSIONS PRODUCED BY HIGH-ENERGY METHODS
With these methods, translucent or bluish appearance
emulsions, nano-emulsions typical feature, with particle
diameters below 200 nm were obtained, as shown in
Figures 1 and 3. For both experiments, particle sizes
greater than 200 nm were obtained when Tween 40 was
used as surfactant.
This could suggest an over-processing by
homogenization, which is consistent with the report by
Jafari et al. (2006), and could be attributed to surfactant
malfunction and increased Brownian motion, which in
turn increased collision probability and coalescence
during homogenization. Under these conditions,
emulsion particle size results from the competition
between two opposing processes: breakage and particle-
particle coalescence. Particles’ coalescence rate is
determined by surfactant ability to rapidly adsorb to
newly formed particles surface (Tadros et al., 2004;
McClements, 2004).
The low-energy method used in this work is not a feasible
way to prepare nano-emulsions for the materials used; oil
composition influences the ability to produce nano-
emulsions with this method. High-energy methods can be
used to obtain nano-emulsions with particle diameters
smaller than 200 nm. In systems where globule sizes greater
than 200 nm were obtained suggest an over-processing by
homogenization.
REFERENCES
Abismaïl, B., Canselier, J. P., Wilhelm, A. M., Delmas, H., y Gourdon, C. (1999).
Emulsification by ultrasound: drop size distribution and stability. Ultrasonics
Sonochemistry 6, 75-83.
Acosta, E. (2009). Bioavailability of nanoparticles in nutrient and nutraceutical
delivery. Current Opinion in Colloid & Interface Science. 14, 3–15.
Gutiérrez, J.M., González, C., Maestro, A., Solè, I., Pey, C.M., Nolla, J. (2008). Nano-
emulsions: New applications and optimization of their preparation. Current Opinion
in Colloid y Interface Science 13, 245–251.
Jafari, S. M., He, Y., y Bhandari, B. (2006). Nano-emulsion production by sonication
and microfluidization – A comparison. International Journal of Food Properties 9(3),
475–485.
Sarduní, N., Solans, C., Azemar, N., García-Celma, M.J. 2005. Studies on the
formulation of O/W nano-emulsions by low-energy emulsification methods, suitable
for pharmaceutical applications. European Journal of Pharmaceutical Sciences 26,
438-445.
Sonneville-Aubrun, O., Simonnet, J. T., y L’Alloret, F. (2004). Nanoemulsions: A new
vehicle for skincare products. Advances in Colloid and Interface Science 108–109,
145–149.
Tadros, T., Izquierdo, R., Esquena, J., y Solans, C. (2004). Formation and stability of
nano-emulsions. Advances in Colloid and Interface Science 108–109, 303–318.
Fig. 1. Particle size obtained based on surfactant concentration
(%) using high energy methods: a) high pressure
homogenization; b) Probe-type ultrasound.
Pre-emulsion
High Energy Methods
ABSTRACT
To design nano-emulsions loaded with active compounds that allows an increased release and absorption by the organism .The objective of this work is to prepare a nano-structured emulsion using different high and low energy
processes, using high pressure homogenization and sonication as high energy processes and method for low energy, with different surfactant concentrations. In this study, opaque creamy emulsions with particule size greater than
200 nm were obtained using a low energy method. Destabilization presented few minutes after they were obtained, suggesting that oils used in this work, cannot be used to obtain nano-emulsions through this method. Otherwise
translucent emulsions with particle size in a range of 80 to 200 nm were obtained using high energy methods, showing that high energy methods are good methods to obtain nano-emulsions.
If collision time is shorter than adsorption time, an
interface built by newly formed particles is not
completely covered with surfactant, leading to fusion. In
our case, collision rate was greater than the rupture of
particles, resulting in a net increase in particle size.
EMULSIONS PRODUCED BY A LOW-ENERGY METHOD
For this method opaque and creamy dispersions were
obtained and the particle size was greater than 800 nm
(0.8 µm). These emulsions became unstable within
minutes of preparation. These data suggests that this
method could have some restrictions, because in
contrast to results obtained by emulsions with milky
appearance were obtained.
RESULTS & DISCUSSION
MATERIALS AND METHODS
INTRODUCTION
CONCLUSIONS
Low Energy Methods
Homogenizer
APV-1000
Dual Effect
P=400 Bar
5 cycles
Probe type
Ultrasound
Sonifier Model
S250D
80 W
t=10 min
Sarduní et al.,
2005.
Emulsion particle
Coulter LS 230 after
diluting the emulsion
with distilled water
1500 rpm , t= 10 min
Silverson model L4R
homogenizer
0
50
100
150
200
250
300
60 70 80 90
Particlesize(nm)
Surfactant Concentration (%)
Canola/Span 20
Canola/Tween 40
AEN/Span 20
AEN/Tween 40
0
500
1000
1500
2000
2500
3000
3500
4000
60 70 80 90
Particlesize(nm)
Surfactant Concentration (%)
Canola/Span 20
Canola/Tween 40
AEN/Span 20
AEN/Tween 40
Figure 2. Particle size obtained based on surfactant
concentration (%) using a low-energy method
Canola Oil and Orange
essential Oil were
purchased in comercial
brands
These authors obtained translucent or transparent nano-
emulsions with particle sizes up to 45 nm with 2000 rpm.
Particle sizes obtained are depicted in Figures 2 and 3.
Low-energy methods use the chemical energy stored in
the system and a phase transition takes place during
emulsification (Sarduní et al, 2005; Gutierrez et al., 2008).
It has been shown that its composition is important in
order to obtain nano-emulsions.
ANOVA analysis showed significant differences between
low and high energy methods. High energy methods
resulted better for nano-emulsion preparation.
0
200
400
600
800
1000
1200
60 70 80 90
Particlesize(nm)
Surfactant Concentration (%)
Canola/Span 20
Canola/Tween 40
AEN/Span 20
AEN/Tween 40
Figure 3. Appearance of emulsions obtained with high-energy
(a) and low energy methods (b).
a) b)
a)
b)