Phase Behaviour Study of Pitaya Seed Oil: Jojoba Oil with Non-Ionic Surfactants in Emulsion System

Abstract

Pitaya seed contains good antioxidant capacity while jojoba contains many different varieties of tocopherols which make up Vitamin E to promote healthy and clear skin. The phase behaviour of systems has been investigated by constructing ternary phase diagrams consisting of pitaya seed oil: jojoba oil/non-ionic surfactant/water. Different HLB value of non-ionic surfactants exhibit different ternary diagram characteristics. A lower HLB shows a more oil-soluble and a more water-soluble surfactant (larger homogeneous and isotropic region in ternary phase diagrams) whereas high value of HLB shows the reverse of that result. The results showed that the Tween85 gave better solubility in water to produce larger isotropic and homogeneous regions for jojoba oil, pitaya seed oil and pitaya seed oil: jojoba oil. The presence of optimal HLB value of Tween85 for the stabilization of o/w emulsions contributes to the enlargement of the single phase regions.

Full text

ASIAN JOURNAL OF CHEMISTRY
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2015.18891
INTRODUCTION
As unique as its appearance, pitaya contains the charac-
teristic of health properties. Essential fatty acids, namely,
linoleic acid and linolenic acid form a significant percentage
of the unsaturated fatty acids of the seed oil extract. Essential
fatty acids (EFA) are important acids that are necessary in
diet. However, two essential fatty acids, linolenic and linoleic
acid cannot be synthesized in the body and must be obtained
from food. Previous studies on red and white Malaysian
Hylocereus seeds, after thermal degradation of fruit cells for
seed separation, revealed high contents of linoleic acid and
nutritionally favourable low ratios of saturated fatty acids1,2.
Due to its high contents of unsaturated fatty acids, like linoleic
acid and the presence of vitamin E, pitaya seed oil may repre-
sent an interesting source for the food and cosmetic industries.
Due to its high levels of linoleic acid, pitaya seed oil may help
in relieving rough skin and maintaining heath of the body’s
protective barrier1.
Other than pitaya seed oil, jojoba oil is one of the natural
products used in the emulsion system. Jojoba oil is extracted
from the seed of Jojoba plant with binomial name of
Simmondsia chinensis. Jojoba is a desert shrub that grows wild
in southern Arizona, north-western Mexico and neighbouring
areas. Jojoba is grown commercially for its oil, a liquid wax
ester that used widely in cosmetic, pharmaceutical, textile and
Phase Behaviour Study of Pitaya Seed Oil: Jojoba Oil with Non-Ionic Surfactants in Emulsion System
SITI SALWA ABD GANI1,2,*, NORSUHAILI KAMAIRUDIN2, RAWAIDA LIYANA RAZALLI1 and MAHIRAN BASRI1
1Department of Chemistry, Faculty of Science, University Putra Malaysia, Selangor, Malaysia
2Halal Products Research Institute, University Putra Malaysia, Selangor, Malaysia.
*Corresponding author: Fax: +60 3 89466997; Tel : + 60 3 89468431; E-mail: ssalwaag@upm.edu.my; ssalwa.abdgani@gmail.com
Received: 1 December 2014; Accepted: 1 January 2015; Published online: 26 May 2015; AJC-17273
Pitaya seed contains good antioxidant capacity while jojoba contains many different varieties of tocopherols which make up vitamin E to
promote healthy and clear skin. The phase behaviour of systems has been investigated by constructing ternary phase diagrams consisting
of pitaya seed oil: jojoba oil/non-ionic surfactant/water. Different HLB value of non-ionic surfactants exhibit different ternary diagram
characteristics. A lower HLB shows a more oil-soluble and a more water-soluble surfactant (larger homogeneous and isotropic region in
ternary phase diagrams) whereas high value of HLB shows the reverse of that result. The results showed that the Tween85 gave better
solubility in water to produce larger isotropic and homogeneous regions for jojoba oil, pitaya seed oil and pitaya seed oil: jojoba oil. The
presence of optimal HLB value of Tween85 for the stabilization of o/w emulsions contributes to the enlargement of the single phase
regions.
Keywords: Pitaya seed oil, Jojoba oil, Non-ionic surfactant, Phase diagram, Emulsion system.
Asian Journal of Chemistry; Vol. 27, No. 9 (2015), 3452-3456
high-grade lubricant field. Jojoba can be considered as unique
oil due to its extremely long structure (C36-C46) straight-chain
wax ester and not a triglyceride. Since it is composed of wax
esters, it is an extremely stable substance and does not easily
deteriorate and the structure closely resembles that of your
own skin sebum, making it an excellent moisturizer and ideal
for all skin types. Jojoba oil is favourite oil used as a massage
medium because it acts as an emulsifier with the skin’s natural
sebum and gently unclogs the pores and lifts grime and
imbedded impurities. It contains myristic acid which also has
anti-inflammatory actions and since it has similarity in
composition to that of the skin’s own oils, it is quickly absorbed
and is excellent for dry and mature skins as well as inflamed
conditions.
An emulsion is a mixture of two or more liquids that are
normally immiscible which contains both a dispersed and a
continuous phase, with the boundary between the phases called
the “interface”. Emulsion is the most common delivery system
used in cosmeceutical field. Wide variety of ingredients can
be prepared in the emulsion formed. Their properties enable
the ingredient to be delivered and absorbed to the skin conve-
niently. The emulsions are made by dispersing oil in water
using amphiphilic emulsifiers, which have hydrophilic and
lipophilic terminals that enable the molecules to interact with
both oil and water, by assembling themselves at the oil-water
interface. The stable emulsions are best formulated with

emulsifiers or combinations of emulsifiers, which possess HLB
values close to the required HLB of the oil phase. However,
the chemical type of emulsifier also can affect the stability of
the emulsions. Emulsions with ionic surfactant are stable by
electrostatic repulsion between the micelles whereas for the
non-ionic surfactant the stability is achieved due to the steric
repulsion. Ternary phase diagram consists of three components
system and formed by dispersing the mixed emulsifier in
water without the addition of an oil phase and can be prepared
to represent the continuous phase of the corresponding emul-
sion3.
Surfactant also known as surface active agent is the
substance that has the tendency to concentrate at the surface
or interfaces and lowering the surface tension (or interfacial
tension) between two liquids or between a liquid and a solid.
Surfactant molecules have either one tail or two; those with
two tails are said to be double-chained. Different in structure
most commonly according to polar head group that classified
the surfactant into four types; which are anionic, cationic,
amphoteric and non-ionic. The “tail” of most surfactants is
fairly the same, consisting of a hydrocarbon chain, which can
be branch, linear, or aromatic.
Non-ionic surfactants do not have an electrical charge,
which makes them resistant to water hardness deactivation.
They have been widely used in domestic and industrial deter-
gents and related products4. These surfactants are excellent
grease removers that are used in laundry products, household
cleaners and hand dishwashing liquids. Most non-ionic
surfactants are considered to be more effective in cleaning
applications at low concentration and in removing oily soil
from synthetic fabrics. Non-ionic surfactants can be classified
into three categories: polyethylene oxide, poly (ethylene/
propylene) oxide and polyhydric alcohol, based on their
hydrophilic groups. The examples of non-ionic surfactants
were polyoxyethylene(20) sorbitan tri-oleate (Tween85) and
[olyoxyethylene(20) sorbitan mono-oleate (Tween80). The
HLB value of Tween85 and Tween80 are 11 and 15 respec-
tively. The efficiency of a surfactant is not determined solely
by the amphilicity; it also depends on the HLB characteristics
for this compound5.
The aim of this work was to study the phase behaviour of
pitaya seed oil: jojoba oil with non-ionic surfactant by
constructing the ternary phase diagram using five different
non-ionic surfactants.
EXPERIMENTAL
Pitaya fruit was purchased from Great Sun Farm Pitaya,
Teluk Panglima Garang, Selangor. The composition of pitaya
seed oil are linoleic acid (49.6 %), oleic acid (21.6), palmitic
acid (17.9 %) and stearic acid (5.49 %)1 pitaya seeds were
finely ground before being extracted with hexane. The fine
ground seeds were soaked in hexane solution for 24 h in room
temperature. Upon completion of oil extraction, hexane was
discarded from the oil in the rotary evaporator. Sorbitan tri-
oleate (Tween85) and sorbitan mono-oleate (Tween 80) were
purchased from Fluka Chemie GmbH, USA. Hexane (HPLC
grade) was obtained from Fisher Chemicals, UK. Jojoba
oil was purchased from Making Cosmetics, Inc., USA with
compositions of Eicosenoic acid (80.0 %), Palmitic acid
(3.0 %), oleic acid (15.0 %) and linoleic acid (5.0 %), SA
Handbook.6 Deionized water was prepared in our laboratory.
Construction of ternary phase diagram: Pitaya seed
oil: jojoba oil /non-ionic surfactant/deionized water were
weighed ranging from 0:100 to 100:0 (pitaya seed oil: jojoba
oil /non-ionic surfactant/ deionized water (w/w). The mixture
with a total weight of 0.5 g was placed in a 10 mL screw-cap
glass tube. The samples were then vortexed using vortex
mixture for 5 min and then centrifuged for 15 min at 4000
rpm. The phase behaviours of the samples were examined
through cross-polarized light. The experiment was repeated
with the addition of deionized water according to its percentage
from 0 to 100 %. The phase behaviours were determined from
visual observation. Ternary phase diagrams were drawn accor-
dingly.
Effect of phase behaviour of pitaya seed oil: Jojoba oil
with respect to different non-ionic surfactants: Two non-
ionic surfactants were selected to construct ternary phase dia-
gram of pitaya seed oil: jojoba oil. They were polyoxyethylene
(20) sorbitan tri-oleate (Tween85) and polyoxyethylene (20)
sorbitan mono-oleate (Tween80). The HLB value of Tween85
is 11.0 and Tween80 is 15.0. Comparison among the ternary
phase diagrams were made to see the changes that happened
when the different HLB values of the non-ionic surfactants
were used.
RESULTS AND DISCUSSION
Phase behaviour study of pitaya seed oil: Jojoba oil
with respect to different non-ionic surfactants: Emulsion
was produced by mixing two or more immiscible liquid which
in this context referred to water and oil. The mixing of oil,
water and emulsifier in different ratio can produce different
types of emulsion systems. Emulsion also depends on the
chemical nature, molecular structure and concentration of
surfactants and other ingredients7. The mixtures of different
surfactants have many industrial applications because they
show better characteristic than their building units. Non-ionic
surfactants in general Tween and Span in particular are safe
agents for all biological tissue in general and for skin in
specific8. These non-ionic emulsifiers are compatible with
various ingredients used in the preparation of emulsions and
are not affected by pH. They are supposed to have an enhance-
ment effect on the skin barrier9. Construction of ternary phase
diagrams is the best way to study all types of formulation.
In the study of phase behaviour of pitaya seed oil with
jojoba oil using different non-ionic surfactants, six ternary
phase diagrams were constructed. Jojoba oil, pitaya seed oil
and pitaya seed oil: jojoba oil conditions were tested with
different HLB values. The surfactants were Tween80 and
Tween85, having HLB values of 15.0, 11.0 respectively. The
changes of phase behaviour were observed in the ternary phase
diagram.
Phase behaviour of T80/jojoba oil/deionized water:
Fig. 1 depicts the ternary phase diagram of Tween80/jojoba
oil/ deionized water. Tween80 carried the HLB value of 15.0
is higher compared to Tween85, in constructing the ternary
phase diagram. Fig. 1 showed the presence of three regions
Vol. 27, No. 9 (2015) Phase Behaviour Study of Pitaya Seed Oil: Jojoba Oil with Non-Ionic Surfactants in Emulsion System 3453

10
20
30
40
50
60
70
80
90 10
20
30
40
50
60
70
80
90
10 20 30 40 50 60 70 80 90
W
ater O
il
Tween 80
Fig. 1. Ternary phase diagram of Tween80/jojoba oil/water. (L – Isotopic
region; T2p – Two phase region; TT – Three phase region)
with different percentage of mixtures, the regions were isotropic
(L), two phase (T2p) and three phase (TT) regions. The isotropic
region was found along the apex line of deionized water from
2 to 90 %. The formation of one phase region suggested that
the surfactant mixtures were able to lower the surface tension
between the aqueous phase and oil phase, hence facilitates the
formation of emulsions having a milky appearance10. Two-
phase region donated as T2p domain covers most of the T80
and jojoba oil apex line. This showed the instability and
incompatibility in the emulsion system. The three phase region
appeared at a water-rich corner and at low percentage of
Tween80. Even though Tween80 is the best surfactant to form
an o/w emulsion in the system, the formations of two and three
phases are still exists.
Phase behaviour of Tween85/jojoba oil/deionized
water: Fig 2 shows the phase diagram of phase behaviour of
Tween85/jojoba oil/deionized water. The HLB value of
Tween85 (11.0) is lower compared to Tween80 (15.0). Four
phases were observed in this phase diagram. The homogenous
region, milky emulsion system was found at the water rich
corner in the system, meanwhile in Tween80/jojoba oil/
deionized water system, there is no homogenous region found.
This is because for the stabilization of oil-in-water emulsions,
surfactant with HLB value in the range 9-12 are optimal5 and
suitable for emulsification. In the isotropic regions, clear
emulsion system was appeared in two areas. The largest area
was found along the apex line of Tween85 from 5 to 90 %.
Second area was found at the middle of the ternary phase
diagram. The two phase region cover along Tween85 and
jojoba oil apex line. The two phase regions domination also
appeared when using Tween80 as an emulsifier. The three
phase region was found at the water-rich corner in the system.
This was due to the increasing in the percentage of deionized
water. The area for three-phase region was rather small com-
pared to Tween80 phase diagram.
10
20
30
40
50
60
70
80
90 10
20
30
40
50
60
70
80
90
10 20 30 40 50 60 70 80 90
W
ater O
il
Tween 85
Fig. 2. Ternary phase diagram of Tween85/jojoba oil/deionized water. (Th
– Homogenous region; L – Isotopic region; T2p – Two phase region;
TT – Three phase region)
Phase behaviour of Tween80/pitaya seed oil/water: The
phase diagram of Tween80/pitaya seed oil/deionized water is
shown in Fig. 3. A distinct one-phase region, isotropic region
was observed. The isotropic region was found along the apex
line of Tween80 and deionized water from 0 to 94 % and covers
the most apex line of Tween80 and pitaya seed oil. The isotropic
region occurred are larger compared to the ternary phase diagram
of Tween80/jojoba oil/deionized. The rest of the region consisted
of two phase and three phase regions. Most of the two-phase
region appeared at the middle of the system. The formation of
two and three phases was due to the mixture being unable to
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
10 20 30 40 50 60 70 80 90
Water O
il
Tween 80
Fig. 3. Ternary phase diagram of Tween80/pitaya seed oil/deionized water.
(L – Isotopic region; T2p – Two phase region; TT – Three phase
region)
3454 Gani et al. Asian J. Chem.

mix well and formed one phase mixture. The three-phase region
appeared at the low percentage of Tween80 with the percentage
of deionized water at 92 % and above.
Phase behaviour of Tween85/pitaya seed oil/deionized
water: Fig. 4 depicts the ternary phase diagram of Tween85/
pitaya seed oil/deionized water. Four phases were observed in
this ternary diagram compared to Tween80. The homogenous
region was appeared at the water rich corner in the system.
The isotropic region was found along the apex line of Tween85
and deionized water from 4 to 70 %. The two-phase region
covers along Tween85 and jojoba oil apex line. The two-phase
region appeared in the middle of the system. The three-phase
region was found at the water-rich corner in the system. It has
a larger area compared to Tween85/jojoba oil/deionized water
phase diagram. Pitaya seed oil works well with both Tween80
and Tween85. However there are more isotropic region, are
formed in Tween80/pitaya seed oil/deionized water compared
to Tween85/pitaya seed oil/deionized water. Whereas, the
Tween85 formed both single-phase which is homogenous, the
milky phase and isotropic, the clear phase.
10
20
30
40
50
60
70
80
90 10
20
30
40
50
60
70
80
90
10 20 30 40 50 60 70 80 90
W
ater O
il
Tween 85
Fig. 4. Ternary phase diagram of Tween85/pitaya seed oil/deionized Water.
(Th – Homogenous region; L – Isotopic region; T2p – Two phase
region; TT – Three phase region)
Phase behaviour of Tween80/pitaya seed oil: jojoba
oil/deionized water: Fig. 5 shows the ternary phase diagram
of Tween80/pitaya seed oil: jojoba oil/deionized water. The
isotropic region, single-phase was found along the apex line
of Tween80 and deionized water from 6 to 85 %. The formation
of a large two phase region was observed on the middle of
ternary phase diagram. The reason of the inability of the
surfactant to facilitate the emulsification process was probably
due to no synergistic effect of the surfactant in enhancing the
surface activity11. Three phase region also appeared at water-
rich corner in the ternary phase diagram. It has high percentage
of Tween80 and low percentage of pitaya seed oil: jojoba oil.
10
20
30
40
50
60
70
80
90
10
20
30
40
50
60
70
80
90
10 20 30 40 50 60 70 80 90
W
ater O
il
Tween 80
Fig. 5. Ternary phase diagram of Tween80/pitaya seed oil/de-ionized water.
(L – Isotopic region; T2p – Two phase region; TT – Three phase
region)
The ternary phase diagram of Tween80/pitaya seed oil: jojoba
oil/deionized water is quite similar to Tween80/jojoba oil/
deionized water phase diagram.
Phase behaviour of Tween85/pitaya seed oil: Jojoba
oil/deionized water: Fig. 6 depicts the ternary phase diagram
of Tween85/pitaya seed oil: Jojoba oil/deionized water. Similar
to previous Tween85 ternary phase diagram, four phases were
able to be observed. The homogenous region was appeared at
water rich corner in the system having a quite large area. The
emulsion formed could be classified as oil in water emulsion
as the percentage of deionized water was higher than the
percentage of oil. The isotropic region was found along the
apex line of Tween85 and deionized water from 4 to 70 %.
The two-phase region covers along Tween85 and jojoba oil
apex line. The two-phase region appeared in the middle of the
system. The three phase region was found at the water-rich
corner in the system.
This study demonstrated the importance of selecting a
surfactant with proper HLB for specific oil. The types and
properties of surfactant will determine the types of emulsion
formed. The HLB number could be used as a reference and
guidance to determine whether the surfactant is suitable to
use for several types of emulsions or not. In general, surfactants
with lower HLB numbers (4-6) are mostly used as emulsifiers
(water-in-oil), while those with higher HLB numbers (10-15)
are detergents and surfactants with HLB numbers between 7
and 9 are suitable for wetting agents12. However, in this study
we wish to form an oil-in-water emulsion. According to Griffin’s
theory, to select a surfactant properly for any application, one
must have the optimal HLB value and the correct chemical
group. For the stabilization of oil-in-water emulsions, surfac-
tant with HLB value in the range 9-12 are optimal5 and
Vol. 27, No. 9 (2015) Phase Behaviour Study of Pitaya Seed Oil: Jojoba Oil with Non-Ionic Surfactants in Emulsion System 3455

10
20
30
40
50
60
70
80
90 10
20
30
40
50
60
70
80
90
10 20 30 40 50 60 70 80 90
W
ater O
il
Tween 85
Fig. 6. Ternary phase diagram of Tween85/pitaya seed oil: Jojoba oil/ de-
ionized water. (Th – Homogenous region; L – Isotopic region; T2p
– Two phase region; TT – Three phase region)
suitable for emulsification. Both surfactants were suitable
surfactants and formed good results which have HLB numbers
(10-15), however Tween85 produced a better result and works
well for all three types of oil by forming two single phases
which is homogenous and isotropic phase.
Conclusion
Pitaya seed oil was successfully extracted using n-hexane.
In this research, six ternary phase diagrams of pitaya seed oil:
jojoba oil with non-ionic surfactants was successfully cons-
tructed. The results showed that the Tween85 gave better
solubility in water to produce larger isotropic and homo-
geneous regions for jojoba oil, pitaya seed oil and pitaya seed
oil: jojoba oil. The presence of optimal HLB value of Tween85
for the stabilization of o/w emulsions contributes to the
enlargement of the single phase regions.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge to Department of
Chemistry, Faculty of Science, University Putra Malaysia for
providing adequate facilities for carrying out the research work.
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