ORIGINAL ARTICLE Effect of Oil Content and Composition on the Gelling Properties of Egg-SPI Proteins Stabilized Emulsion Gels Mengqi Zhang 1,2,3 & Yanjun Yang 1,2 & Nuria C. Acevedo 3 Received: 14 April 2020 /Accepted: 30 June 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract Effects of different oils on the rheological properties, textural profile, water loss (WL), oil loss (OL) and microstructure of egg- soybean protein isolate (SPI) stabilized emulsion gels were investigated at neutral pH, wherein soybean oil, olive oil and menhaden oil were used to form emulsions. The results showed that viscosity of emulsions progressively increased with the increase of oil content. Similarly, analysis of the rheological behavior of the formulated emulsion gels revealed an increase in the mechanical strength (G’) with the increase in oil concentration, indicating that oil droplets played a significant role in the formation of the gel structure. In addition, at high levels of oil, the hardness and chewiness of emulsion gels were also high, while a slight decrease in springiness and cohesiveness were observed. A linear relationship between hardness and water/oil loss was found, whereas the Pearson correlation suggested that less drainage of water may slow down the outflow of oil. The microstructural images showed a more compact network as a result of the increase of oil content in the formulation. Scarce significant differences were found among emulsion gels formulated with different oil type, suggesting oil composition played a dispensable role on the gelling properties of emulsion gels. Keywords Egg-SPI composite proteins . Oil composition . Oil-emulsion gel . Rheology . Microstructure Introduction Protein-stabilized emulsion filled gels, or emulsion gels, have recently attracted increasing interest because of their practical applications in food formulations [1]. For example, emulsion gel systems can be used as controlled-release carriers, espe- cially for lipid-soluble bioactive substances, thus extending the possibilities to create foods with new and improved prop- erties. Numerous studies have been conducted on emulsion gels formed by soybean proteins, whey proteins and milk proteins [2–10]. As an ingredient in emulsion gels, oil plays an important role in the texture of the system, imparting viscosity and taste. Oil droplets contained in gelled protein food systems have been categorized as active or inactive filler particles depend- ing on their interaction with the surrounding gel matrix [11]. Active filler particles have hydrophilic surfaces and are inte- grated into the composite gel; whereas inactive particles have more hydrophobic surfaces and show little interaction with the matrix [2]. At small rheological deformation conditions of the gel, active filler particles cause the elastic modulus to increase with the increase in the volume fraction whereas inactive filler particles cause the elastic modulus to decrease [2, 11, 12], which is an easy way to distinguish active and inactive filler particles. It is known that the textural properties of emulsion gels are dependent on many factors, such as the method used to pre- pare the gels, protein components, protein concentration and oil content [6, 8, 10]. The common methods for forming gels are heat treatment, acidification and enzyme treatment [13], and suitable methodologies are chosen according to the mate- rials and the purpose of the experiment. The influence of dif- ferent β-conglycinin/glycinin ratio on the properties, micro- structure and gelling mechanism of soy globulin-stabilized * Yanjun Yang yangyj@jiangnan.edu.cn * Nuria C. Acevedo nacevedo@iastate.edu 1 State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, People’s Republic of China 2 School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, People’s Republic of China 3 Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA Food Biophysics https://doi.org/10.1007/s11483-020-09646-8