Preparation and characterisation of water-soluble phytosterol nanodispersions Wai-Fun Leong a,b , Oi-Ming Lai c , Kamariah Long d , Yaakob B. Che Man a , Misni Misran e , Chin-Ping Tan a,⇑ a Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, UPM, 43400 Serdang, Selangor, Malaysia b School of Science, Monash University, Sunway Campus, Jalan Lagoon Selatan, 46150 Bandar Sunway, Selangor, Malaysia c Department of Bioprocess Technology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, UPM, 43400 Serdang, Selangor, Malaysia d Malaysian Agricultural Research & Development Institute (MARDI), P.O. Box 12301, 50774 Kuala Lumpur, Malaysia e Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia article info Article history: Received 27 March 2010 Received in revised form 5 March 2011 Accepted 8 April 2011 Available online 16 April 2011 Keywords: Phytosterol Nanodispersions Mean particle diameter Primary homogenisation High-pressure homogenisation abstract The purpose of this study was to prepare and characterise water-soluble phytosterol nanodispersions for food formulation. The effects of several factors were examined: four different types of organic phases (hexane, isopropyl alcohol, ethanol and acetone), the organic to aqueous phase ratio and conventional homogenisation vs. high-pressure homogenisation. We demonstrated the feasibility of phytosterol nan- odispersions production using an emulsification–evaporation technique. The results showed that hexane was able to produce the smallest particle size at a mean diameter of approximately 50 nm at monomodal distribution. Phytosterol nanodispersions prepared with a higher homogenisation pressure and a higher organic to aqueous phase ratio resulted in significantly larger phytosterol nanoparticles (P< 0.05). Phy- tosterol loss after high-pressure homogenisation ranged from 3% to 28%, and losses increased with increasing homogenisation pressure. Elimination of the organic phase by evaporation resulted in a phy- tosterol loss of 0.5–9%. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Phytosterols, which are cholesterol analogues, are classified as functional lipids. These compounds are found exclusively in plants, especially in their oil and fat fractions. Presently, commercial phy- tosterols are primarily by-products from vegetable oil refining and the wood pulp industry. Phytosterols or dietary plant sterols are well-known hypocholesterolemic agents (Clifton et al., 2004; Klingberg et al., 2008). Reduction in serum cholesterol has been re- lated to the reduction of cardiovascular disease risk. Some studies have also demonstrated that daily consumption of phytosterols is associated with decreased cancer risk (Awad, Chinnam, Fink, & Bradford, 2007; Méric et al., 2006). Although phytosterols are widely found in diets rich in plant matter, the amounts of phytos- terols acquired from a normal diet range from 160 to 430 mg/day (Ostlund, 2002), which is barely adequate for obtaining a signifi- cant health benefit. For this and other reasons, phytosterols have become an interesting ingredient for use as food supplements and in food formulation. The application of phytosterols in food formulation is rather challenging, as they are neither hydrophilic nor lipophilic in nature. Although phytosterols are more soluble in fats and oils than in aqueous solutions, the amount of phytoster- ols soluble in the fat and oil phase is small. Although the esterifica- tion of phytosterols has enhanced their solubility in the oil phase, applications of phytosterols or their esterified forms are limited to high-fat food products. Consumers who expect to benefit from the serum cholesterol–lowering effects would therefore have to con- sume high-fat food regardless of the associated health hazards of a high fat diet. An emulsion system could be a better approach. Phytosterols made into a water-soluble form by emulsification can be applied in a wider range of food products. Some studies have reported that the cholesterol–lowering effects of emulsified phytosterols are similar to that of esterified or non-esterified phy- tosterols but at smaller doses (Meguro et al., 2001; Ostlund, Spil- burg, & Stenson, 1999). Nano-size dispersion, which is an attractive dispersion system compared to the conventional micro-size emulsion system, could be a more promising solution. Despite the fact that nanotechnolog- ical research is still at its early stages, the growth of food nanotech- nology has been rather speedy over the past few years (Chau, Wang, & Wen, 2007). Nanodispersion has many applications as a delivery system in the pharmaceutical, cosmetic and food indus- tries. Nanodispersions are typically transparent or translucent dis- persions, consisting of very fine particles, ranging from a few nanometres to a few 100 nm in size, that disperse in the respective continuous phase. Particle sizes of less than 100 nm have been tar- geted, due to their ability to be applied to various delivery systems (Acosta, 2009). Changes of the physical states of the bioactive ingredients affect their properties and usage in the formulation. Scientists have been working toward understanding nano-range material for the past two decades. For example, Cheong, Tan, 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.04.027 ⇑ Corresponding author. Tel.: +60 3 89468418; fax: +60 3 89423552. E-mail addresses: tancp@putra.upm.edu.my, tcping@yahoo.com (C.-P. Tan). Food Chemistry 129 (2011) 77–83 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem