A Journal of the ASEAN Committee on Science & Technology Vol. 31, No.1, 2014

 

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ABOUT THE ASEAN JOURNAL ON SCIENCE AND TECHNOLOGY FOR DEVELOPMENT The ASEAN Journal on Science and Technology for Development is a refereed Journal of the ASEAN Committee on Science and Technology (ASEAN COST). It reports on science and technology policies and programmes, and research activities undertaken by COST in support of social and economic development of the ASEAN member countries. The coverage is focused but not limited to, the main areas of activity of ASEAN COST, namely, Biotechnology, Non-Conventional Energy Research, Materials Science and Technology, Marine Sciences, Meteorology and Geophysics, Food Science and Technology, Microelectronics and Information Technology, Space Applications, and Science and Technology Policy, Infrastructure and Resources Development. ABOUT THE ASEAN COMMITTEE ON SCIENCE AND TECHNOLOGY The ASEAN Committee on Science and Technology was established to strengthen and enhance the capability of ASEAN in science and technology so that it can promote economic development and help achieve a high quality of life for its people. Its terms and reference are: ●● To generate and promote development of scientific and technological expertise and manpower in the ASEAN region; ●● To facilite and accelerate the transfer of scientific and technological development among ASEAN countries and from more advanced regions of the world to the ASEAN region; ●● To provide support and assistance in the development and application of research discoveries and technological practices of endogenous origin for the common good, and in the more effective use of natural resources available in the ASEAN region and in general; and ●● To provide scientific and technological support towards the implementation of existing and future ASEAN projects. Information on the activities of ASEAN COST can be obtained at its website http://www.asnet.org DISCLAIMER While every effort is made to see that no inaccurate or misleading data, opinion or statement appears in the Journal, articles and advertisements in the Journal are the sole responsibility of the contributor or advertiser concerned. They do not necessarily represent the views of the Editors, the Editorial Board nor the Editorial Advisory Committee. The Editors, the Editorial Board and the Editorial Advisory Committee and their respective employees, officers and agents accept no responsibility or liability whatsoever for the consequences of any inaccurate or misleading data, opinion or statement. © Copyright 2013: ASEAN Committee on Science and Technology No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form of by any means, without permission in writing from the copyright holder.

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Editorial Board Editor-in-Chief School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia Prof Emeritus Dr Md Ikram Mohd Said Editorial Board Members Malaysia Dr Ahmad Ibrahim Assoc. Prof Tan Tin Wee Academy of Sciences Malaysia Prof Abdul Halim Shaari Prof Thong Kwai Lin Department of Biochemistry, National University of Singapore Thailand Prof Narongrit Sombatsompop Faculty of Science, Universiti Putra Malaysia Institute of Biological Science, Faculty of Science/UMBIO Cluster, Institute of Graduate Studies, University of Malaya Brunei Darussalam Rosita Abdullah School of Energy, Environment and Materials, King Mongkut’s University of Technology, Thonburi Prof Prida Wibulswas Cambodia Pal Des President, Shinawatra University Senior Special Duties Officer, Ministry of Development Assoc. Prof Zohrah Sulaiman Vice-Rector, Royal University of Phnom Penh Indonesia Dr Warsito Purwo Taruno Deputy Vice-Chancellor, Universiti Brunei Darussalam Myanmar Dr Zaw Min Aung Minister, Special Advisor for Research and Cooperation Lao PDR Kongsaysy Phommaxay Director General, Department of Technical and Vocational Education, Ministry of Science and Technology Philippines Dr Carol M. Yorobe Acting Director General, Cabinet Office of the Ministry of Science and Technology Keonakhone Saysuliane Undersecretary for Regional Operations, Department of Science and Technology Singapore Assoc. Prof Ong Sim Heng Acting Director General, Department of Information Technology Vietnam Dr Mai Ha Department of Electrical and Computer Engineering, National University of Singapore Director General, Ministry of Science and Technology

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Editorial Advisory Panel Brunei Darussalam Eddie Sunny Lao PDR Dr Maydom Chanthanasinh Deputy Permanent Secretary, Ministry of Development Myanmar Dr Ko Ko Oo Deputy Minister, Ministry of Science and Technology, National COST Chairman Singapore Prof Low Teck Seng National COST Chairman, Deputy Minister, Ministry of Science and Technology Cambodia Dr Om Romny National COST Chairman, Managing Director, Agency for Science, Technology and Research Thailand Assoc. Prof Weerapong Pairsuwan Director, Institute of Technology of Cambodia Philippines Dr Graciano P. Yumul Deputy Permanent Secretary, Ministry of Science and Technology Malaysia Dr Noorul Ainur Mohd Nur Undersecretary for R&D, Department of Science and Technology Indonesia Prof Syamsa Ardisasmita, DEA National COST Chairman, Secretary General, Ministry of Science, Technology and Innovation Vietnam Dr Le Dinh Tien Deputy Minister for Science and Technology Network, National COST Chairman Deputy Minister for Science and Technology, National COST Chairman Editor/Technical Editor Ex-Academy of Sciences Malaysia Academy of Sciences Malaysia Amirul Ikhzan Amin Zaki Kanesan Solomalai Production Manager Universiti Putra Malaysia Kamariah Mohd Saidin Publisher Universiti Putra Malaysia Press

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Contents ASEAN J. Sc. Technol. Dev. Volume 31(1), 2014 Fabrication, Rheology and Antioxidant Activity of Palm Esters-based Emulsions Loaded with Tocotrienol S. H. Ng, B. Mahiran and I. Zahariah Pd(II) Complexes with Nitrogen-oxygen Donor Ligands: Synthesis, Characterization and Catalytic Activity for Suzuki-Miyaura Cross-Coupling Reaction M. T. Amalina, B. Hadariah, K. Karimah and W. I. W. Nazihah Cigarette Smoking among Male Teenagers in Malaysia ― A Narrative Review R. III P. Dioso Forecsting of Hydrological Time Series Data with Lag-one Markov Chain Model M. A. Malek and A. M. Baki Assessment Attributes on Effective Construction Management for Property Developers in Malaysia Ayob Norizam, M.A. Malek and I. Mohamad 1 15 24 31 38

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ASEAN J. Sci. Technol. Dev.,  31(1): 1 – 14 Fabrication, Rheology and Antioxidant Activity of Palm Esters-based Emulsions Loaded with Tocotrienol S. H. NG *, B. MAHIRAN AND I. ZAHARIAH 1 2 3 Palm oil esters are wax esters derived from palm oil and oleyl alcohol. Palm oil esters have many applications due to their luxurious moisturizing properties, non-greasy and blend easily with fragrances and colours when applied on skin surface. The aim of this research was to fabricate palm esters-based emulsions cream for topical delivery, characterise the rheological properties and in vitro antioxidant activity of the palm esters-based emulsions system. Emulsions containing palm oil esters loaded with tocotrienol were obtained in two stages, with propagation of rotor-stator at 6000 r.p.m. for 5 min and further emulsified using an ultrasound at various acoustic amplitudes for another 5 min. A stress/rate controlled Kinexus Rheometer with a temperature controller was used to measure the rheological properties of the emulsion. Rheology measurements were performed at 25.0°C ± 0.1°C with 4°/40 mm cone and plate geometry. The in vitro antioxidant activity was investigated using UV-Vis spectrophotometer. The yield stress of the emulsions increased with increasing acoustic amplitudes. The viscoelasticity of the emulsions were enhanced by the increase in the oil and surfactant concentrations. The emulsions with higher oil phase concentration [30% (w/w)] showed greater elasticity which implied strong dynamic rigidity of the emulsions. The cohesive energy increased significantly with surfactant concentration especially for the emulsions with 30% (w/w) oil phase concentration. The palm oil esters emulsions containing tocotrienol gave higher Trolox equivalent antioxidant capacity values which implied higher antioxidant capability. The tocotrienol in emulsion with 30% (w/w) dispersed phase showed that they were the most stable with longest shelf life and exhibited greater inhibitory effects on the ABTS•+. Key words: Emulsion; rheological properties; antioxidant activity; yield stress; cohesive energy; palm oil esters; tocotrienol Palm oil is produced from the fruit of oil palm (Elaeis guineensis) which is grown in mass plantations in tropical countries such as Malaysia, Indonesia and Nigeria. The oil consists of 95% triglycerides and 5% diglycerides whereby carbons of the carboxyls range from 10–20 with or without double bonds (Tanaka et al. 2008). Palm oil esters (POEs) are a constituent of modified form of palm olein oil known simply as palm oil. Desirable characteristics of fat esters including 1 2 non-toxicity, good fat solubility properties and excellent wetting at interfaces (Radzi et al. 2006) but without the greasy feeling when applied on the skin surface; these have attracted the attention of the industry. The emollient effect of POEs had been proven thereby making this oil highly recommendable for its incorporation into the topical preparation as oil phase. Thus, palm oil esters are excellent ingredient to be used in cosmeceutical and pharmaceutical formulations. School of Pharmacy, International Medical University, 57000 IMU Bukit Jalil, Kuala Lumpur, Malaysia Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia 3 Sime Darby Research Sdn. Bhd Carey Island, 42960 Pulau Carey, Selangor, Malaysia * Corresponding author (e-mail: sookhan_ng@imu.edu.my)

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ASEAN Journal on Science and Technology for Development, 31(1), 2014 Nanoemulsions are emulsion with droplet size in the range 20 nm–200 nm (Solans et al. 2003). They are independent of molecular size of the hydrophilic solute and the nature of the aqueous phase. In addition, nanoemulsions delivery system was independent of animal skin characteristics such as the stratum corneum thickness and the follicle-type (Wu et al. 2001). Thus, nanoemulsions due to their extremely small size are suitable to be used as delivery system in cosmeceuticals. However, nanoemulsions are only kinetically stable and therefore, it is also a very fragile system by nature (Tadros et al. 2004). As they are transparent and usually very fluid, the slightest sign of destabilization easily appears. They become opaque and creaming may be visible. Thus, stability of the nanoemulsion is a critical factor to be analysed. The achievement of developing long time stability of cosmetic products (3-years shelf life) is often difficult and deeply affects costs in the development of new formulations. Rheology is an independent scientific discipline: studying the deformability, and flow properties of a matter under an applied stress or strain is revealed by McClements (1999). Owing to the fact that rheology can give a better picture of the behaviour of a material, it is therefore widely used as a tool to test the texture and flow behaviour of industrial products especially in the processing industries such as food (Lorenzo et al. 2008), cosmetics (Bummer & Godersky 1999), pharmaceuticals (Zumalacarregui et al. 2004), polymer (Karg et al. 1985), coating (Kikic et al. 1979), and oil processing (Martin et al. 2006). The rheological results also enable scientists to estimate the product’s quality such as elasticity, viscosity, deformability, storage, shelf life including intermolecular interactions due to ultra-sensitivity at microstructure of materials. Antioxidants neutralize damaging free radicals by quenching reactive molecules and, thus protecting cells from both endogeneous 2 stress (byproducts of cellular energy) and exogenous stressors (ultraviolet light, pollution, cigarette smoke etc.) (Choi & Berson 2006). Tocotrienol are fat-soluble vitamins related to the family of tocopherols. Tocopherol and tocotrienol are well recognized for their antioxidative effect (Kamal 1996). This effect depends primarily on the phenolic group in the chromanol ring, rather than the side chain (Burton & Ingold 1989). The trolox equivalent antioxidant capacity (TEAC) assay is widely applied to assess the amount of radicals that can be scavenged by an antioxidant, i.e. the antioxidant capacity (Lien et al. 1999). The present investigation was focused on the preparation of palm esters-based emulsions of tocotrienol and to characterise the rheological properties of the emulsion systems. Furthermore, assessment of the in vitro antioxidant activity of esters-based palm was done by the TEAC assay. EXPERIMENTAL Materials POEs was prepared in the laboratory according to the method of Keng et al. (2009) Sorbitan monooleate (Span® 80) and polyoxethylene (20) sorbitan monooleate (Tween ®80) were purchased from Merck, Germany. The HLB values of sorbitan monooleate (Span ® 80) and polyoxethylene (20) sorbitan monooleate (Tween® 80) are 4.3 and 15.0, respectively. Tocotrienol (Gold Tri. E 70) was from Golden Hope Bioganic, Malaysia. Xanthan gum from Xanthomonas campestris was obtained from Fluka Chemie GmbH, France. Freshly deionized water was obtained from water deionizer, Mili-Q (Milipore, USA). Methods Preparation of emulsions containing tocotrienol. Emulsions were formulated using POEs containing tocotrienol as dispersed oil phase and Mili-Q water as the continuous aqueous phase. Xanthan gum was dispersed in deionized

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S.H. Ng et al.: Fabrication, Rheology and Antioxidant of Palm Esters-based Emulsions with Tocotrienol water at 0.8% (w/w). Preparation of dispersed oil phase was performed by homogenizing 5% (w/w) of surfactants into oil phase with a Polytron homogenizer (Kinematica GmbH, Germany) rotor stator. The ratio of Span ® 80:Tween® 80 was 1:4. The preparation was continued by adding the oil phase dropwise to the aqueous solution with continuous homogenized at 6000 r.p.m. for 5 min. The temperature was lowered to 40°C. At 40°C, the active ingredient was added. The emulsions were further homogenized using ultrasonic cavitation for 5 min. The sonifier tip horn was adjusted to 2 cm below the surface of a 100 ml sample. Rheology measurement . A stress/rate controlled Kinexus Rheometer (Malvern Instrument, UK) with a temperature controller, was used to measure the rheological properties of the emulsion. The measurements were performed at 25.0 ± 0.1°C with 4°/40 mm cone and plate geometry. The samples were allowed to relax for 10 min after being loaded to the plate before the measurement was started. In vitro antioxidant activity. The antioxidant activity was assessed as described below. Experiments were performed on the Varian Cary 50 UV-Vis spectrophotometer (Varian, Australia). Trolox (2.5, 5.0, 10.0, 15.0 μM) was prepared in ethanol. Ascorbic acid was prepared in 18 MΩ water to a concentration of 10.0, 15.0, 20.0 μM and α-tocopherol in ethanol at 10.0, 15.0, 20.0 μM. ABTS, 2,2’-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt was dissolved in water to a 7 mM concentration. ABTS radical cation (ABTS +) was produced by reacting ABTS stock solution with 2.45 mM potassium persulphate (final concentration) and allowing the mixture to stand in the dark at room temperature for 12 h–16 h before use. The radical was stable in this form for more than two days when stored in the dark at room temperature. ABTS.+ solution was then diluted with ethanol to an absorbance 3 of 0.70 (± 0.02) at 734 nm and equilibrated at 30°C (Roberta et al. 1999). Diluted ABTS.+ solution (1.0 ml) (A734 nm = 0.700 ± 0.020) was added to 10 μl of antioxidant compounds or Trolox standards in ethanol. The absorbance of the sample was taken at 30ºC every min after initial mixing up to 6 min. An appropriate solvent blanks were run in each assay. All determinations were carried out three times, and in triplicate, on each occasion and at each separate concentration of the standard and samples. The percentage inhibition of absorbance at 734 nm was calculated and plotted as a function of concentration of antioxidants and of Trolox for the standard reference data (Roberta et al. 1999). RESULTS AND DISCUSSION Rheological Properties of Emulsions System Steady-state flow: The sensitivity of emulsions to shearing. The sensitivity of these emulsions to shearing was tested in steadystate flow. The greater the yield stress σY, the more brittle the emulsion, and this leads to believe that the emulsion either undergoes disorganization of its structure or takes longer to recover its initial states. Figures 1 and 2 summarize the yield stress data as a function of acoustic amplitudes (%) and surfactant concentration [% (w/w)], respectively. The yield stress of the emulsions increased with increasing acoustic amplitudes. The increase in acoustic amplitudes (20% to 100%) led to decrease in mean droplet size. The decrease of droplet size leads to the increase in the total droplet surface area. When the total surface area of the droplet increased, the strength of the attractive force will also increase. Thus, greater stress is required to initiate flow when high attractive force is holding the droplets resulting high viscosity with high yield stress (Pal 1996). Mean droplet size was another factor affecting the flow behaviour of the emulsion.

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8 7 Yield stress (Pa) 6 5 4 3 2 1 0 20 40 60 Amplitude (%) Figure 1. The yield stress of the emulsions as a function of acoustic amplitudes and oil phase concentration. Emulsions with 10% ( ), 20% ( ) and 30% ( ) oil phase concentration. 80 100 10 8 Yield stress (Pa) 6 4 2 0 4 6 8 10 Surfactant concentration [% (w/w)] Figure 2. The yield stress of the emulsions as a function of surfactant concentration. Emulsions with 10%( ), 20% ( ) and 30% ( ) oil phase concentration. 4

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S.H. Ng et al.: Fabrication, Rheology and Antioxidant of Palm Esters-based Emulsions with Tocotrienol The yield stress of the emulsions increased with surfactant concentration ( Figure 2 ) indicating structural integrity arising from the strong colloidal interaction between the droplets. The yield stress is the stress that has to be overcome before the emulsion starts to flow (Barnes 1999). The system with higher surfactant concentration tends to form a denser interfacial layer, which is incompressible (Hamill & Petersen 1966). Hence, the droplets in such sterically stabilized system are usually characterized as ‘hard sphere’ (McClements 1999). The strength of interaction forces (mainly the attractive and repulsive interactions) between the droplets for the hard sphere system (high surfactant concentration system) was relatively greater than the one with lower surfactant concentration. In the absence of the strong sterically repulsive effect, the droplets in the emulsions system with lower surfactant concentration were able to pack more efficiently even at low shear. Therefore, the droplets were aligning themselves easily with the shear field to initiate flow. This explained that the increase in surfactant concentration led to increase in yield stress of emulsion system. Oil phase concentration in an emulsion system is another factor affecting the flow behaviour (Akhtar et al. 2005). The attractive force is one of the colloidal interactions which play an important role in the increase in viscosity and yield stress. The magnitude of viscosity and yield stress depend on the strength of the attractive force between the droplets (Pal 1996). Higher strength of attractive force between the droplets leads to increase in viscosity and yield stress. Shear Stress versus Shear Rate Profile The shear stress—shear rate profile of stabilized emulsions are depicted in Figure 3. Much like viscosity—shear rate profile, the rate of change of shear stress depends largely on the rate of change of shear rate. As depicted in Figure 3, at zero shear rate the shear stress responses are not zero. This suggested that these emulsions were shear thinning non-ideal plastic-like material, with yield stress (σY) response. In other words, they behaved like pseudoplastic material, which implied that flow can only be induced on these emulsions with the application of certain minimum amount of stress called yield stress. Figure 3 shows that above the yield stress these samples assume a linear shear stress—shear rate relationship. This in turn suggested that, these emulsions did not follow ideal Newtonian flow behaviour even at high shear rate domain. By contrast, the shear stress—shear rate relationship increased exponentially with a certain power law exponent at low-shear rate domain below yield stress, suggesting that the flow behaviour of these emulsions resembled that of plastic-like material at these low shearrate domain. As far as the effect of concentration on yield stress was concerned, these profiles suggested that yield stress increased monotonically with surfactant concentration. This in turn indicated that all samples examined here exhibited non-Newtonian model type fluid behaviours, implying that the viscoelastic force dominated over the elastic force, and that the emulsions under investigation underwent structural deformation with shear rate irrespective of surfactant concentration. The increase in the yield stress as a function of surfactant concentration further indicated that emulsions with higher surfactant concentration possess higher degree of material structuring as opposed to lower surfactant concentration. This also means that emulsions with higher surfactant concentration offer a larger resistance to external force before they started flowing. This in turn suggested that emulsions stabilized with higher surfactant concentration undergo a greater degree of deformation under applied shear in comparison to emulsions stabilized with lower surfactant concentration. 5

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Shear stress (Pa) Shear rate (s-1) (a) Shear stress (Pa) Shear rate (s-1) (b) Shear stress (Pa) Shear rate (s-1) (c) Figure 3. Effect of shear rate of emulsions on the shear stress for (a) 10% (b) 20% (c) 30% oil phase concentration. Surfactant concentration: 5% ( ); 6% ( ); 7% ( ); 8% ( ); 9% ( ) and 10% ( ). 6

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S.H. Ng et al.: Fabrication, Rheology and Antioxidant of Palm Esters-based Emulsions with Tocotrienol Oscillatory Measurements: Strain Sweep Profile A critical strain (γc) is the maximum applied strain where the emulsion still gives a linear response to shear stress with constant elastic modulus. The critical strain, γc of emulsions in different oil phase concentration is shown in Figure 4. The γc of the emulsions increased with the oil volume fraction and surfactant concentration. The γ c was increased 50%, 46% and 86% as the surfactant concentration was increased from 5% to 10% (w/w) for emulsions with 30%, 20% and 10% (w/w) oil phase concentration, respectively. On the other hand, the γc increased more than 100% when the oil concentration was increased from 10% to 30% (w/w). The increase of critical strain of emulsion with 30% (w/w) oil phase concentration when the surfactant concentration was increased implied that the highly packed droplets have developed a strong structure due to the high interdroplet interaction between the droplets which corresponded to the droplet size and droplet concentration of the emulsions system. Since the strength of the interdroplet interactions corresponded to the mean separation distance between the droplets, the highly packed emulsion system will therefore has greater interdroplet interaction forces. The high interdroplet interaction strength was able to hold the droplets and withstand the large deformation forces applied during the strain sweep test. The strain sweep profiles also provided information about the elastic component of the emulsions. Figures 5 and 6 show increasing trends in the elastic modulus ( G′ ) of the emulsions with surfactant and oil concentration indicating that the interactions between droplets are relatively strong. A trend of increasing elastic modulus accompanying the increased of γc was observed. The cohesive energy (Ec) within the linear viscoelastic regime for when G′ is in phase with the applied strain amplitude can also be obtained (Bossard et al. 2007), as shown below: (1) 35 30 Critical strain (γc) 25 20 15 10 5 0 5 6 7 8 9 10 Surfactant concentration [% (w/w)] Figure 4. The critical strain, γc of the emulsions as a function of surfactant concentration. Emulsions with 10% ( ), 20% ( ) and 30% ( ) oil phase concentration. 7

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Elastic modulus, G’ (Pa) Shear strain (%) (a) Elastic modulus, G’ (Pa) Shear strain (%) (b) Elastic modulus, G’ (Pa) Shear strain (%) (c) Figure 5. The linear viscoelastic region of the emulsions with a series of surfactant concentration [5% ( )]; [6% ( )]; [7% ( )]; [8% ( )]; [9% ( )] and [10% ( )] for (a) 10%, (b) 20% and (c) 30% oil phase concentration. 8

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S.H. Ng et al.: Fabrication, Rheology and Antioxidant of Palm Esters-based Emulsions with Tocotrienol When σ equals G′ in the linear viscoelastic region, the cohesive energy is defined as: (2) Tadros (2004) explained that the cohesive energy was related to the structure of the emulsion system, which correlated to the droplet size and number of contact area between the droplets. The droplet concentration and the packing of the droplets influenced the strength of the cohesive force. As discussed before, the number of droplets was increased as the oil concentration was increased from 10% to 30% (w/w) at fix surfactant concentration. As a result, the number of contacts area within the droplets increased. Thus, increases in the cohesive energy of the emulsions system were observed. Ec ranged from a low 0.13 J/m3 for emulsion with 5% (w/w) surfactant concentration in 10% (w/w) oil phase concentration to a high of 15.88 J/m3 for emulsion with 10% (w/w) surfactant concentration in 30% (w/w) oil 45 40 Elastic modulus, G’ (Pa) 35 30 25 20 15 10 5 0 0 2 4 phase concentration. Ec was low for emulsion with 5% (w/w) surfactant concentration in 10% (w/w) oil phase concentration as the elasticity was low (Figure 6). The higher the cohesive energy, the more stable a system was as the elastic strength was basically a measure of the strength of the internal structure. This in turn demonstrated that the emulsion samples under examination were stable systems, and that the stability of these emulsions systems was enhancing with decreasing droplet size. Figure 7 show that the cohesive energy increased significantly with surfactant concentration especially for the emulsions with 30% (w/w) oil phase concentration. The dramatic increase of cohesive force was due to the highly packed systems related to the interdroplet interactions that had been previously discussed. In vitro Antioxidant Activity The concentration-response curve for six sequentially and separately prepared stock standards of Trolox was illustrated in 6 8 10 12 Surfactant concentration [% (w/w)] Figure 6. The elastic modulus of the emulsions as a function of surfactant concentration. Emulsions with 10% ( ), 20% ( ) and 30% ( ) oil phase concentration. 9

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