Journal of Food Engineering 275 (2020) 109871 Available online 18 December 2019 0260-8774/© 2019 Elsevier Ltd. All rights reserved. Effect of salt on the inter-relationship between the morphological, emulsifying and interfacial rheological properties of O/W emulsions at oil/ water interface Mahmut Do� gan a, b, * , Meryem G€ oksel Saraç c , Duygu Aslan Türker a a Erciyes University, Engineering College, Department of Food Engineering, Kayseri, Turkey b TAGEM Food Analysis Center Co., Erciyes University Technopark Area, Kayseri, Turkey c Cumhuriyet University, Yıldızeli Vocational College, Food Technology Department, 58500, Sivas, Turkey A R T I C L E INFO Keywords: Emulsion stability Interfacial rheology Oil-in-water emulsion Salt Emulsifer ABSTRACT The role of salt in oil-in-water emulsion is not widely studied, but relevant to food processing, formulation and sensory properties. The interaction between the emulsifer and salt could impart an important effect on the emulsion stability and rheology. This present study aimed to determine the interfacial rheology of oil-in-water emulsions that were stabilized by different salts and affected by the different emulsifers that promote the interfacial layer. In addition, this study intended to investigate whether the droplet size and zeta potential functioned as contributing parameters. Two salts (sodium chloride-NaCl and calcium chloride-CaCl 2 ) and three emulsifers (lecithin, mono-diglycerides, sodium steoryl-2-lactylate) were chosen to select appropriate combi- nations for oil-in-water emulsions. The relationship between the interfacial properties and the O/W emulsion stability in the presence of salt was assessed by both optical microscopy and visual observation of phase sepa- ration throughout the storage. As a result, it was found that the interfacial storage (G i ’) and loss modulus (G i ’’) values were dependent on the frequency. This result suggested that the oil/water interfaces support the conformational reconstruction of emulsifer changes to take advantage of improved hydrophobicity which results from the frequency dependence of the surface modules. The stability of emulsions prepared with the presence of CaCl 2 was found to be higher than the emulsions prepared with NaCl which can be attributed to the counter ions effects of the CaCl 2. The steady, dynamic and interfacial rheological measurements were consistent with ζ-po- tential, creaming and morphological observations. The results of this study also demonstrated that the interfacial rheology data might be predictive of emulsion stability and CaCl 2 salt will increase the stability of the product with the different emulsifers in the food formulations. 1. Introduction Emulsions occurs with two immiscible fuids and stabilized by emulsifers in the interfacial area (Dridi et al., 2017). Emulsions fnd applications in dairy, meat, cereal products, salad dressing and desserts for the processing, formulation and sensory properties, thereby emul- sion processes are widely used in the food industry (Castel et al., 2017; Erdmann et al., 2017; Soleimanpour et al., 2013). On the other hand, the emulsion systems are utilized in agriculture, cosmetic and pharmaceu- tical industries (Lett et al., 2016). Emulsifers generally used to improve stability in dynamically un- stable systems such as emulsions (Dickinson and Golding, 1997). Pro- teins, phospholipids, polysaccharides, and surfactants are utilized in the food industry as an emulsifying agent (Xu et al., 2016). Emulsifers include lecithin and mono-diglyceride that are commonly used and known as ubiquitous emulsifers, as well as sodium steoryl-2-lactylate obtained by specifc applications. Sodium steoryl-2-lactylate is the spe- cial product obtained from the reaction of vegetable oils with sodium salts and acids such as stearic and lactic acids. Lecithin is generally produced from a by-product of edible oil processing (Nguyen et al., 2014) and composed of phospholipids and other vegetable oil fractions such as glycolipids, fatty acids, triglycerides, sterols and carbohydrates which dissolved in neutral oils (van Nieuwenhuyzen and Tom� as, 2008). Mono- and diglycerides are generally produced by hydrolyzed of tri- glycerides (Krog and Sparsø, 2003). The compositions of commercial mono- and diglycerides are different because of their monoglyceride * Corresponding author. Erciyes University, Engineering College, Department of Food Engineering, Kayseri, Turkey. E-mail address: dogan@erciyes.edu.tr (M. Do� gan). Contents lists available at ScienceDirect Journal of Food Engineering journal homepage: http://www.elsevier.com/locate/jfoodeng https://doi.org/10.1016/j.jfoodeng.2019.109871 Received 31 July 2019; Received in revised form 10 December 2019; Accepted 13 December 2019