Effect of Lepidium perfoliatum seed gum addition on whey protein concentrate stabilized emulsions stored at cold and ambient temperature 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 article info Article history: Received 1 November 2011 Accepted 6 June 2012 Keywords: Lepidium perfoliatum seed gum Whey protein concentrate (WPC) Emulsion stability Storage temperature abstract In this study the effect of Lepidium perfoliatum seed gum on the properties of whey protein concentrate (WPC) stabilized corn oil-in-water emulsions at pH 7 was investigated. Various concentrations (0e0.6% w/v) of L. perfoliatum seed gum were used together with 2% (w/v) WPC to emulsify corn oil in water at a ratio of 1:5. Quality attributed such as particle size distribution, creaming profile and coalescence rate during storage at 4 and 25  C; surface and interfacial tension; zeta potential and viscosity of the emulsions were determined. The results indicated that the addition of L. perfoliatum seed gum had no significant effect on zeta potential but the surface and interfacial tension increased with the rise of gum concentration. It was also found that the addition of L. perfoliatum seed gum to WPC emulsions at a critical concentration of 0.2% (w/v) caused flocculation of oil droplets, which resulted in marked increase in particle size and the creaming rate. However at higher gum concentrations beyond this value, the particle size remained constant, apparently because of the high viscosity of the aqueous phase. At all concentrations tested, emulsions stored at 4  C were more stable except for those containing 0.2% L. perfoliatum seed gum. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Oil-in-water emulsions play critical roles in the processing, formulations and sensory characteristics of most food products. They are thermodynamically unstable systems which tend to be destabilized by several mechanisms including flocculation, aggre- gation and coalescence of the dispersed droplets (Dickinson, 1997). Two types of ingredient are essential in the formation stabilization of an emulsion: emulsifier and stabilizer (Dickinson & Galazka, 1992). Protein and polysaccharide are the two most important func- tional biopolymers widely incorporated in food emulsions as ingredient (Ye, Hemar, & Singh, 2004). When used together, they have the ability to control the texture, structure and stability of the emulsion system (Dickinson & McCalements, 1995). Proteins stabilize the oil droplets against coalescence or flocculation as well as reduce the oilewater interfacial tension, which facilitated formation of emulsions (Damodaran, 2005). Whey protein has been reported to aid in the formation and stabilization of oil-in-water (O/W) emulsions (Mangino, 1984) through their adsorption at the watereoil interface (Dalgleish, 1997; Dickinson, 1997; Pearce & Kinsella, 1978). This forms an interfacial layer which is generally charged (because proteins contain charged amino acids) and can also sterically stabilize the oil droplets (Dalgleish, 1997). Proteins are normally used in combination with polysaccharides in order to improve the stability of oil droplets against creaming and other destabilizing phenomena. Polysaccharides are not particularly surface active molecules and are commonly added into emulsions as thickening agents to enhance the viscosity of the aqueous phase and thereby to retard instability mechanisms (Paraskevopoulou, Boskou, & Kiosseoglou, 2005). Considering the cost, availability and functional characteristics of common commercial stabilizers, researchers have increasingly been interested to seed new polysaccharides of local origin. Gum extracted from Lepidium perfoliatum seed has shown promise to be considered as a potential novel food thickening agent, however, very little is understood on its effect when added to food emul- sions (Koocheki, Taherian, & Bostan, 2011). Therefore, the objective of the present study was to investigate the effect of L. perfoliatum seed gum on the properties of whey protein concentrate (WPC) stabilized emulsions, at different storage time and temperatures. For this purpose, zeta potential, interfacial properties, particle size distribution during storage, creaming and viscosity were measured. * Corresponding author. Tel.: þ98 915 313 9459; fax: þ98 511 8787430. E-mail address: koocheki@um.ac.ir (A. Koocheki). Contents lists available at SciVerse ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd 0268-005X/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodhyd.2012.06.004 Food Hydrocolloids 30 (2013) 292e301