Industrial Crops and Products 80 (2016) 77–85 Contents lists available at ScienceDirect Industrial Crops and Products jo ur nal home p age: www.elsevier.com/locate/indcrop Improvement of physical stability properties of kenaf (Hibiscus cannabinus L.) seed oil-in-water nanoemulsions Ai Mun Cheong a , Khang Wei Tan b , Chin Ping Tan c , Kar Lin Nyam a,∗ a Department of Food Science and Nutrition, Faculty of Applied Sciences, UCSI University, 56000 Kuala Lumpur, Malaysia b Faculty of Engineering, Technology and Built Environment, UCSI University, 56000, Kuala Lumpur, Malaysia c Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia a r t i c l e i n f o Article history: Received 15 July 2015 Received in revised form 19 October 2015 Accepted 20 October 2015 Keywords: Kenaf (Hibiscus cannabinus L.) seed oil Nanoemulsions High pressure homogenization Emulsion stability a b s t r a c t Kenaf seed oil-in-water nanoemulsions were optimised using simplex centroid mixture design with three components (sodium caseinate, gum Arabic and Tween 20). In addition, the main, binary and ternary interaction effects among these three selected emulsifiers on physical stability were also studied. The mixture design showed a good fit to the predicted model with R 2 > 0.89, 0.82, and 0.73 for mean particle size, polydispersity index (PDI) and zeta-potential, respectively. The optimum proportion of emulsifier mixtures was 64.9% (w/w) SC, 6.4% (w/w) GA, and 28.7% (w/w) T20 that predicted to produce mean particle size of 126.82 nm, PDI of 0.16 and zeta-potential of −43.47 mV. The experimental value obtained was 121.22 nm, 0.16 and −39.63 mV for mean particle size, PDI, and zeta-potential, respectively. No significant difference (p > 0.05) between the experimental and predicted values, indicating the suitability of the mixture design for optimising and developing stable kenaf seed oil-in-water nanoemulsions. The optimised formulation was stable at both chill (4 ◦ C) and room temperature (25 ◦ C) over 1 month of evaluation. The results have important implications for the development of stable kenaf seed oil-based nutraceutical products. It can be added into beverages such as dairy products to improve the nutrition value of the beverage. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Kenaf (Hibiscus cannabinus L.) is an annual, non-wood fibre plant of the Malvaceae family that was first domesticated in northern Africa (Webber and Bledsoe, 2002). Kenaf is an important crop as a new annually renewable source of industrial fibre in many develop- ing countries, including China, India, Thailand, and Malaysia (Monti and Alexopoulou, 2013). However, kenaf seed oil was not received the same amount of attention as kenaf fibre and feed crop; until recently, it is considered as an important medicinal crop (Monti and Alexopoulou, 2013). Kenaf seed oil contains high amount of mono- and poly-unsaturated fatty acids, primarily oleic acid (37.1%) and linoleic acid (36.6%) (Nyam et al., 2009a). The high oil content, oleic and linoleic acids suggested that kenaf seed oil has poten- tial to be used as good source of edible oil for human consumption (Coetzee et al., 2008). In addition, kenaf seed oil also consists of Abbreviations: SC, sodium caseinate; GA, gum Arabic; T20, Tween 20; PDI, poly- dispersity index. ∗ Corresponding author. Fax: +60 39102 2614. E-mail address: nyamkl@ucsiuniversity.edu.my (K.L. Nyam). numerous of bioactive components, including phytosterols, toco- pherols, polyphenols (Mohamed et al., 1995; Nyam et al., 2009a). However, the poor water solubility, physiochemical instability and susceptible to oxidative deterioration of functional kenaf seed oil during storage owing to its high unsaturated fatty acids content have become major considerations in food and pharmaceutical industry (McClements, 2011). These limitations can be overcome by encapsulation of functional kenaf seed oil by using emulsifier(s) to protect them against lipid oxidation (Nielsen et al., 2013). A fur- ther size reduction to nano-sized emulsion by using high pressure homogenisation (HPH) provides a feasible and efficient approach to improve the solubility, physiochemical stability and bioavailability of functional kenaf seed oil (Adjonu et al., 2014; Ngan et al., 2014) for the application in foods and nutraceutical products. Oil-in-water nanoemulsions are nanometric-sized emulsion with droplet size ranging from 50 nm to 200 nm (Tadros et al., 2004). It is produced by dispersing oil droplets into aqueous phase containing soluble emulsifier with each oil droplet encapsulated by a protective coating of emulsifier molecules (Qian and McClements, 2011). Compared to conventional emulsion, nanoemulsions exhibit better stability to gravitational separation due to its relatively small particle size. This means that Brownian motion effects dominate http://dx.doi.org/10.1016/j.indcrop.2015.10.042 0926-6690/© 2015 Elsevier B.V. All rights reserved.