In vitro evaluation of the structural and bioaccessibility of kenaf seed oil nanoemulsions stabilised by binary emulsifiers and b-cyclodextrin complexes Ai Mun Cheong a , Chin Ping Tan b , Kar Lin Nyam a, * a Department of Food Science with Nutrition, Faculty of Applied Sciences, UCSI University, 56000, Kuala Lumpur, Malaysia b Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia article info Article history: Received 6 April 2016 Received in revised form 1 June 2016 Accepted 4 June 2016 Available online 7 June 2016 Keywords: Kenaf (Hibiscus cannabinus L.) seed oil Lipolysis Releasing behaviour Confocal microscopy Tocopherols Phytosterols abstract Kenaf (Hibiscus cannabinus L.) seed oil contains high nutrition value, suggesting its potential applications in food and nutraceutical fields. However, the poor water solubility and stability strictly limit its appli- cations. A good physical stability of kenaf seed oil-in-water nanoemulsions stabilised by sodium caseinate, Tween 20 and b-cyclodextrin complexes were produced using high pressure homogeniser. A simple model of two-stage dynamic in vitro digestion was employed to investigate the releasing rate of bioactive compounds from kenaf seed oil-in-water nanoemulsions, compared to unencapsulated bulk oil. The particles size and structural changes during digestion were also evaluated. Digested nanoemulsions showed good lipid digestion (85.25%), good bioaccessibility of antioxidants (tocopherols and total phenolic contents) and lower degradation rate of phytosterols compared to digested bulk oil. This study provides good information about the characteristic and release behaviour of formulated kenaf seed oil- in-water nanoemulsions, which is important for the future application in food and nutraceutical industries. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Kenaf (Hibiscus cannabinus L.) seed oil is gaining attention recently owing to its health functional properties. Kenaf seed oil contains high polyunsaturated fatty acids and various bioactive compounds, including phytosterols, tocopherols and polyphenols (Nyam et al., 2009). Tocopherols are important biological lipophilic antioxidants. Tocopherols display protective properties that are associated with polyunsaturated fatty acids and low density lipo- protein from oxidation (Ziani et al., 2012). There is increasing in- terest in the study of incorporation of vitamin E into colloidal system to improve the bioaccessibility and bioavailability. Phytos- terols are plant sterols that do not occur naturally in human body, but are found in seeds, nuts, fruits, and the highest concentration in vegetable oils. Phytosterols have proven to lower serum total cholesterol up to 15% and low density lipoprotein (LDL)-cholesterol concentration up to 22% (García-Llatas and Rodríguez-Estrada, 2011). Besides, phytosterols have been associated with many important pharmacological properties, including anti- inflammatory, anti-atherosclerotic and some types of cancers (García-Llatas and Rodríguez-Estrada, 2011). Squalene is the pre- cursor of phytosterols. It has antioxidant properties, which has been related to anti-inflammatory and anti-cancer effects, partic- ularly for skin cancers. Several in vivo studies have been reported that kenaf seed oil possesses some beneficial pharmacological ef- fects, including anti-cancer (Foo et al., 2012; Wong et al., 2014) and anti-hypercholesterolemic (Ng et al., 2015). The health functional properties of kenaf seed oil suggest that it has high potential to be used as functional foods and nutraceutical products. However, the poor water solubility of kenaf seed oil has limited its bioavailability, which has become a major concern in the application of food and nutraceutical industries. Several approaches have been studied to improve the solubility of kenaf seed oil and its bioaccessibility, such as microencapsula- tion using spray dryer (Ng et al., 2014), microencapsulation using co-extrusion technology (Chew et al., 2015) and nanoemulsions using high pressure homogeniser (Cheong et al., 2016b, 2016c). Abbreviations: O/W, oil-in-water; SC, sodium caseinate; T20, Tween 20; b-CD, b- cyclodextrin; PDI, polydispersity index; DPPH, 2,2-diphenyl-1-picrylhydrazyl; TPC, total phenolic content; FFA, free fatty acids; SGF, simulated gastric fluid; SIF, simulated intestinal fluid. * Corresponding author. E-mail address: nyamkl@ucsiuniversity.edu.my (K.L. Nyam). Contents lists available at ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng http://dx.doi.org/10.1016/j.jfoodeng.2016.06.002 0260-8774/© 2016 Elsevier Ltd. All rights reserved. Journal of Food Engineering 189 (2016) 90e98