Effects of surfactants on the physical properties of capsicum oleoresin-loaded nanocapsules formulated through the emulsion–diffusion method Suvimol Surassmo a,b , Sang-Gi Min a , Piyawan Bejrapha a,b , Mi-Jung Choi a, * a Department of Food Science and Biotechnology of Animal Resources, Konkuk University, Seoul 143-701, Republic of Korea b National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand article info Article history: Received 24 April 2009 Accepted 15 July 2009 Keywords: Nanoemulsion Nanocapsules Capsicum oleoresin Biopolymer Emulsion–diffusion method abstract Capsicum oleoresin encapsulation by poly-e-caprolactone (PCL) was investigated using the emulsifica- tion–diffusion method. Here, the emulsifier concentration affected the characteristics of both the nano- emulsion (NE) and nanocapsules (NCs). The process parameters were optimized by varying the Pluronic Ò F68 (PF68) concentration in the aqueous phase of the formulation. In this research, the optimal param- eters of the preparation process were established, and the physical properties of NE and NC were com- pared. The size of the NC particles decreased according to an increase in the emulsifier concentration. NE showed insignificantly different particle sizes with mean diameters of 320–460 nm depending on the emulsifier concentration. On the contrary, the size of the NC particles prepared with 1.25% PF68 was 5.43 ± 0.29 lm, while the NC with 5% PF68 produced smaller particles (310 nm). The surfactant con- centration also had an important effect on the encapsulation efficiency and release properties of the NCs while maintaining the loading capacity of the capsicum oleoresin. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Herbs and spices are widely used in pharmaceuticals, cosmetics, and the food industry (Edris, 2007). Capsicum oleoresin is derived from a group of pungent plants, namely Capsicum species in the Solanaceae family, or chili peppers, which have capsaicin (8- methyl-N-vanillyl-6-nonenamide) as an active component. Many researchers have reported the benefits of capsaicin or its deriva- tives, such as antiperoxidative properties (Kogure et al., 2002), anti-inflammation (Beltran, Ghosh, & Basu, 2007; Schulte-Mattler et al., 2007; Spicer & Almirall, 2005), and the repellency of biting insects, when delivered in a concentration that is sufficient for it to permeate the tissue (Bryant, 1997). Furthermore, Capsicum sp. have been found to have several beneficial health effects that in- clude the promotion of the following: lipid metabolism through capsaicin’s inhibition of lipid absorption in rat intestines (Kawada, Hagihara, & Iwai, 1986; Materska & Perucka, 2005); diabetes con- trol (Ahuja, Robertson, Dominic, & Madeleine, 2006); digestive function and antioxidant and antiradical activity (Dairam, Fogel, Daya, & Limson, 2008; Howard, Talcott, Brenes, & Villalon, 2000; Suhja, 2006); antitumor activity in the gastrointestinal tract (John- son, 2007); and antibacterial activity (it can inhibit the growth of some foodborne bacteria) (Dorantes et al., 2000). Capsicum oleo- resin is an attractive essential oil that is broadly used as a func- tional substance in the food industry. Therefore, capsaicin has become an important functional material due to increasing de- mand by consumers for its application in foods. In particular, it is used in functional food applications to give foods an enhanced spicy taste, and as an alternative to in-feed additives for antimicro- bial activity as well as to stimulate digestive enzyme secretion from the pancreas along with bile production (Meunier, Cardot, Manzanilla, Wysshaar, & Alric, 2007; Platel & Srinivasan, 2004), and finally, to induce a greater food retention time (Platel & Srini- vasan, 2002). Capsaicin is also used in analgesic creams and defen- sive sprays (Arip, Ahmad, Mokhtar, Taib, & Heng, 2003; Marshall & Doperalski, 1981). In recent decades, the terms ‘‘nano- or submicro-emulsion and encapsulation” have been employed in food science in applications related to ‘‘functional food” and ‘‘nutrient” delivery systems (McClements, 2004). Extensive research has been performed in this area through the general particle designation system, which named ‘‘liposomes”, ‘‘micelles”, ‘‘emulsion”, ‘‘solid lipid nanoparticles (SLN)”, and ‘‘biopolymer nanoparticles (BPN)” as vehicles in terms of nanoparticles. Nanoemulsions consist of two immiscible liquids, usually oil and water, and are prepared with small droplet sizes. The size of nanoemulsion droplets are normally in the range of 20– 500 nm (Fernandez, André, Rieger, & Kühnle, 2004). In addition, in food emulsions, a reduced oil droplet size of below 100 nm in nano- emulsions has the potential to provide a translucent emulsion 0963-9969/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2009.07.008 * Corresponding author. Address: Department of Food Science and Biotechnology of Animal Resources, Konkuk University, 1 Hwayang-ding Gwangjin-gu, Seoul 143- 701, Korea. Tel.: +82 2 450 3680; fax: +82 2 455 1044. E-mail address: foodeng301@paran.com (M.-J. Choi). Food Research International 43 (2010) 8–17 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres