Influence of main emulsion components on the physical properties of corn oil in water emulsion: Effect of oil volume fraction, whey protein concentrate and Lepidium perfoliatum seed gum Marjan Soleimanpour a , Arash Koocheki a, ⁎, Rassoul Kadkhodaee b a Department of Food Science and Technology, Ferdowsi University of Mashhad (FUM), PO Box 91775-1163, Mashhad, Iran b Department of Food Technology, Khorasan Research Institute for Food Science and Technology, PO Box 91735-139, Mashhad-Quchan Highway, Mashhad, Iran abstract article info Article history: Received 12 December 2011 Accepted 5 April 2012 Keywords: Lepidium perfoliatum seed gum Whey protein concentrate (WPC) Oil volume fraction Emulsion Physical properties The effect of composition (whey protein concentrate, Lepidium perfoliatum seed gum, and oil content) of corn oil-in-water emulsions on their physical properties, droplet size and viscosity was studied using response surface methodology (RSM). For each response, a second-order polynomial model was developed using multiple linear regression analysis. The results indicated that the response surface models were significantly fitted for all response variables studied. It was shown that all emulsion components greatly influenced the physical properties of emulsion and its overall stability during storage. The main effect of L. perfoliatum seed gum was observed to be significant in most of response surface models. Therefore, the concentration of this gum should be considered as a critical variable for the formulation of emulsions. The overall optimum region resulted in a desirable emulsion was predicted to be obtained by combined level of 0.59% L. perfoliatum seed gum, 6% WPC and 21.95% oil volume fraction. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Most emulsion products usually contain different components. The efficient production of high quality food emulsions depends on knowledge of the contribution that each individual constituent makes to the overall properties and how this contribution is influenced by the presence of the other constituents (McClements, 2005). Biopolymer ingredients most used in emulsion production are proteins and polysaccharides (Dickinson, 1992, 2003). Since foods are multicompo- nent systems, protein–polysaccharide interactions have been exten- sively researched in order to find new and better applications for these biopolymers (Khalloufi, Corredig, Goff, & Alexander, 2009; Wang, Li, Wang, & Adhikari, 2011; Ye, Hemar, & Singh, 2004). Proteins are present primarily as emulsion forming and stabilizing agent, whereas poly- saccharides are mainly used as thickening and water holding agents. Oil volume fraction is also among the major parameters which could affect the properties of emulsion. Proteins are often used as emulsifiers in emulsion to stabilize droplets against flocculation or coalescence (Ye & Singh, 2006). Whey protein concentrate (WPC) has been widely used as a source emulsifier. During emulsification, protein molecules are rapidly adsorbed onto the newly formed droplet surface and reduce the interfacial tension and provide a protective coating. A polysaccharide is often added to oil-in-water emulsions to enhance the viscosity of the aqueous phase, imparts desirable textural attributes, and stabilizes the droplets against creaming (Dickinson, 1992). Among food polysaccharides, seed gums are the preferred hydrocolloids since these are comparatively cheap, nontoxic, eco- friendly and nonpolluting during production and application. Seed gums are not hydrolyzed in the human digestive tract and therefore are not a source of bioavailable calories. They are able to bind and immobilize a large amount of water thus increasing viscosity, modifying texture and stabilizing product consistency (Koocheki, Kadkhodaee, Mortazavi, Shahidi, & Taherian, 2009; Koocheki, Mortazavi, Shahidi, Razavi, & Taherian, 2009; Koocheki, Taherian, & Bostan, 2011). Lepidium perfoliatum seeds contain a large amount of mucilaginous substances which diffuses out when soaked in water (Koocheki, Taherian, Razavi, & Bostan, 2009). The hydrated gum can be used as a potential thickening and stabilizing agent in food industry. Even though L. perfoliatum seed gum is ideal for stabilizing emulsions (Koocheki, Taherian, et al., 2009), there is a lack of sufficient knowledge on the interactions between WPC and this novel gum. The effect of oil-in-water emulsion component on its droplets characteristics, flow properties and physical stability are important for manufacturing a stable food emulsion. Therefore, the objective of this study was to investigate the effects of L. perfoliatum seed gum concentration and oil volume fraction on emulsions formed with different WPC content at natural pH. In the present study, response surface methodology (RSM) was applied for modeling the possible relationships between the responses and independent variables. In Food Research International 50 (2013) 457–466 ⁎ Corresponding author. Tel.: + 98 915 313 9459; fax: + 98 511 8787430. E-mail address: koocheki@um.ac.ir (A. Koocheki). 0963-9969/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2012.04.001 Contents lists available at SciVerse ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres