• International Journal of Technology (IJTech)
  • Vol 13, No 3 (2022)

Enhancement of the Stability of W/O/W Double Emulsion by Chitosan Modified Rice Husk Silica

Enhancement of the Stability of W/O/W Double Emulsion by Chitosan Modified Rice Husk Silica

Title: Enhancement of the Stability of W/O/W Double Emulsion by Chitosan Modified Rice Husk Silica
Lanny Sapei, Rudy Agustriyanto, Endang Wahyu Fitriani, Zerravym Levy, Cindy Sumampouw

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Cite this article as:
Sapei, L., Agustriyanto, R., Fitriani, E.W., Levy, Z., Sumampouw, C., 2022. Enhancement of the Stability of W/O/W Double Emulsion by Chitosan Modified Rice Husk Silica. International Journal of Technology. Volume 13(3), pp. 584-595

Lanny Sapei Department of Chemical Engineering, Faculty of Engineering, University of Surabaya, Raya Kalirungkut, Surabaya 60293, East Java, Indonesia
Rudy Agustriyanto Department of Chemical Engineering, Faculty of Engineering, University of Surabaya, Raya Kalirungkut, Surabaya 60293, East Java, Indonesia
Endang Wahyu Fitriani Department of Pharmaceuticals, Faculty of Pharmacy, University of Surabaya, Raya Kalirungkut, Surabaya 60293, East Java, Indonesia
Zerravym Levy Department of Chemical Engineering, Faculty of Engineering, University of Surabaya, Raya Kalirungkut, Surabaya 60293, East Java, Indonesia
Cindy Sumampouw Department of Chemical Engineering, Faculty of Engineering, University of Surabaya, Raya Kalirungkut, Surabaya 60293, East Java, Indonesia
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Enhancement of the Stability of W/O/W Double Emulsion by Chitosan Modified Rice Husk Silica

The awareness of the need for healthy food continues to increase, hence, the demand for healthy food is also increasing. Water-in-oil-in-water (W/O/W) double emulsion can provide low-fat emulsion-based products due to a lower fraction of oil compared to the corresponding O/W emulsion. However, the stability of double emulsion has been quite tricky to be established due to the presence of two interfacial layers between oil and water. This research aims to study the use of biosilica in the form of rice husk ash (RHA) combined with both chitosan particles and chitosan solution to stabilize the interfacial layer between oil droplets and the outer aqueous phase. The concentrations of chitosan and biosilica, as well as pH of the outer aqueous phase in the acidic ranges, were varied to obtain W/O/W emulsion with higher stability. The primary emulsion was prepared by using the emulsifier mixtures of Tween 20 and Span 80. The resulting primary emulsion was subsequently dispersed into the outer aqueous phase, loaded with the combination of biosilica and chitosan particles/ solution. Emulsification processes were conducted using a rotor-stator homogenizer. The resulting W/O/W emulsions with high stability of ~80-100% were obtained by using the combination of 0.5% biosilica and 1.25% chitosan particles/ 5.25% chitosan solution at the pH of 4. The use of biosilica and chitosan seemed promising to be applied in the manufacturing of healthier food emulsion-based products.

Chitosan; Emulsion; pH; Rice husk silica; W/O/W


The emulsion has been widely found in many diverse processed foods both in the forms of oil-in-water (O/W) and water-in-oil (W/O) emulsions. One of those examples is mayonnaise which is an oil in water emulsion and contains a high concentration of oil of about 60 to 70% (Morley, 2016). However, nowadays the demand for healthier food products with much lower oil content has been increasing. The oil content was reduced in W/O/W emulsion, leading to the development of lower-calorie foods with acceptable taste (Yildirim, 2016).

    Pickering emulsion has recently gained an attraction to reduce the use of polymeric emulsifiers since it had demonstrated higher stability against shear stress and changes in pH or temperatures (Yang et al., 2017). The particles could form multilayers which act as a physical barrier against coalescence. Moreover, the particles were much more strongly deposited on the interfacial layers in contrast to the polymeric emulsifiers which tend to easily detach from the interfaces with time (Aveyard et al., 2003). Pickering emulsion has increasingly been investigated to be used in different fields such as food, pharmacy, and cosmetics (Muharam et al., 2015; Shah et al., 2016; Wu et al., 2020). Several particles which have been used for Pickering emulsions were silica, clays, polymer latex, magnetic particles, graphene, and polymethylpolymethylmethacrylate particles (Lee & Choi, 2018; Bao et al., 2019). The use of silica for the stabilization of O/W emulsion has been widely investigated (Sapei et al., 2017a; Sapei et al., 2017b; Sapei et al., 2018; Sapei, 2020). However, the use of bare silica was not effective and had to be combined with the use of polymeric emulsifiers to help its adsorption onto the interfacial layers (Pichot et al., 2012; Sapei et al., 2017a; Sapei et al., 2017b).

    Chitosan is a biopolymer derived from chitin which is biodegradable, biocompatible, not toxic, and has mucoadhesive properties (Muharam et al., 2015; Krisanti et al., 2020). Chitosan as a polycationic biopolymer may be acted as an emulsifier and emulsion stabilizer through adsorption of the protective layer at oil-water interfaces, viscosity enhancement, and interaction with surface-active agents (Klinkesorn, 2013). Chitosan behaved as a weak cationic polyelectrolyte at pH < 6.5 when most of its amino groups were protonated (Tiraferri et al., 2014; Bhutto et al., 2021). At higher pH of about 7-8, dissolved chitosan was able to strengthen the interfacial layer O/W emulsion due to the polymer chains aggregation (Mwangi et al., 2016). Silica accumulated in living tissues generally referred to as biosilica was amorphous and tended to be hydrophilic due to the presence of hydroxyl groups on their surface (Sapei et al., 2008; Dhaneswara et al., 2019; Sapei, 2020). It is well known that natural silica particles are negatively charged in pure water. As the pH was increased above pH 2, the silica surface developed a net negative charge primarily due to the deprotonation of the silanol group (Dyab, 2012). The high positive charge on -NH3 groups of chitosan when dissolved in aqueous acidic media at pH < 6.5 would likely adhere to negatively charged surfaces such as anionic polysaccharides and synthetic polyanions to give polyelectrolyte complexes and multilayer surfaces (Klinkesorn, 2013; Tiraferri et al., 2014).  Furthermore, O/W emulsion was stabilized by silica particles of which hydrophobicity was modified by chitosan particles addition (Alison et al., 2016; Alison et al., 2018). The hydroxyl groups of silica were suggested to play an important role in the interaction with the polyelectrolyte of chitosan in the formation of a stable adsorption layer (Tiraferri et al., 2014). Furthermore, the stability of W/O/W stabilized by silica-chitosan was dependent on pH since pH may have affected particle charge and rheological properties of the emulsion (Klinkesorn, 2013; Alison et al., 2016). At acidic pH, rice husk silica tended to be chargeless (Sapei et al., 2018) which may have limited its interaction with chitosan. On the other hand, the positive charges of chitosan tended to be decreased as pH was progressing towards neutral pH (Tiraferri et al., 2014; Mwangi et al., 2016; Alison et al., 2018). The chitosan concentration may have affected its adsorption behavior on the silica surface (Li & Xia, 2011; Tiraferri et al., 2014). A recent study demonstrated the use of chitosan solution to coat the oil globules which entrapped insulin-containing internal aqueous phase due to polyelectrolyte complex formation with alginate present in the outer aqueous phase (Faghmous et al., 2020). This chitosan-coated W/O/W multiple emulsion seemed to be promising to be developed as a drug delivery system.

Chitosan can be applied for bodyweight reduction, maintenance of LDL-cholesterol, amelioration of inflammation, and reduction of intestinal transit time according to the European Food Safety Authority (Manigandan et al., 2018). Biosilica could also be used as a food additive and used for biomedical applications because of its health benefits (Alshatwi et al., 2015). The electrostatic interaction between oppositely charged chitosan and biosilica particles has not been extensively explored yet. Let alone its role in strengthening the interfacial layer between oil and water, which became the main concern in this article. This principle has been exploited in wastewater treatment using the coagulation-flocculation process described in the recent studies (Bahrodin et al., 2021; Fard et al., 2021; Iloamaeke et al., 2021). The pollutant removal efficiency was highly dictated by the wastewater pH depending on the coagulant agent and its mechanism (Bahrodin et al., 2021; Sibiyaet al., 2021). Alum as the coagulant became soluble and positively charged in the acidic environment was easily adsorbed onto the negatively charged surface of the colloids leading to charge neutralization and pollutant removal (Bahrodin et al., 2021). Furthermore, the color removal efficiency increased as pH decreased from 10 to 2 when Mercenaria mercenaria shell with a zero-point charge value (pHzpc) of 7.8 used as the coagulant became positively charged thus, enhancing the coagulation of negatively charged colloid particles making them to floc due to the increase in the force of attraction which led to charge neutralization (Iloamaeke et al., 2021). In this research, rice husk silica in combination with chitosan was used to stabilize food-based W/O/W double emulsion. Chitosan both as particles and solution were combined with biosilica and their different mechanisms dependent on pH were studied. Chitosan, both as particles and as a solution, was combined with biosilica, and the various mechanisms dependent on pH were investigated. It is expected that the outcome of this research will be useful for the development of healthier and low-calorie emulsion-based novel food products. 


The stability of W/O/W double emulsion stabilized by rice husk silica was much improved from approximately 60% to about 80-100% when chitosan in the form of particles and solution was added into the outer aqueous phase, respectively. The stabilization mechanisms seemed different between those added with chitosan particles and those added with soluble chitosan. Chitosan particles electrostatically adsorbed on the silica particles at the oil-water interfaces forming a rigid barrier thus preventing flocculation and coalescences of globules. On the other hand, soluble chitosan drastically enhanced the viscosity of the outer aqueous phase thus retarding the flocculation and coalescence rates of oil globules. The pH of the outer aqueous phase played an important role in dictating the positive charge of chitosan particles and the negative charge of silica particles thus influencing the extent of their electrostatic attraction. The pH 4 seemed optimal for achieving W/O/W double emulsion with high stability. The presence of the inner aqueous phase within the microstructure of W/O/W double emulsion was more pronounced at pH 4 compared to those prepared at another pH. The chitosan concentration also affected the overall stability of the W/O/W double emulsion. Fewer chitosan particles seemed preferable to have effectively adhered to the silica particles while increased soluble chitosan was advantageous for improving the viscosity of the outer aqueous phase. The combination of rice husk silica and chitosan as emulsifiers of the secondary emulsions seemed potential to be used for the development of low-calorie and healthy food emulsion-based products.


    We thank Ms. Dyah Ayu Ambarsari for the technical assistance. The research was funded by Ministry of Research and Technology/ National Research and Innovation Agency of the Republic of Indonesia under the research grant scheme of “Fundamental Research” 2020 (contract number: 027/SP-Lit/LPPM-01/RistekBRIN/Multi/FT/III/2020).

Supplementary Material
R3-CE-4752-20210812111021.JPG Effect of pH on the stability of W/O/W emulsion stabilized with 0.5% rice husk silica and 1.25% chitosan particle
R3-CE-4752-20210812111050.jpg Illustrated mechanisms of W/O/W emulsion stabilization by mixing rice husk silica and chitosan in two forms in the outer aqueous phase. A) chitosan particle; B) chitosan solution

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