Abstract
Stability is one of the key quality parameters of emulsion systems, which goes a long way in predicting the shelf life of emulsion products. In this study, the effect of emulsifier (soy protein concentrate (SPC) + maltodextrin (MDX)), dispersed phase (lycopene in oil solution) and homogenizer speed on emulsion stability were investigated and optimized using response surface methodology (RSM). Independent variables were lycopene content (10-20%, w/w), SPC+ MDX as emulsifier and surfactant (30-40%, w/w) and the homogenizer speed (14000-18000 rpm). Responses were droplet size, viscosity and creaming index as stability indicators of the emulsions. According to RSM analysis and models, optimized variables showed a good fit to quadratic equations for droplet size and viscosity with correlation coefficients (R2) of 0.9571 and 0.9826, respectively. After model simplification with backward stepwise solution, the R2 values for droplet size and viscosity decreased slightly to 0.9504 and 0.9826, respectively. Creaming values were fitted properly with linear model, and R2 was 0.8030. Graphical optimization methods were adapted for preparing the best lycopene emulsifying conditions and were predicted to be: homogenizer speed of 18000 rpm; lycopene content of 20% w/w, and SPC+MDX concentration of 36.95% w/w.
Highlights
Oil-in-water emulsions are systems that are composed of two immiscible liquids such as oil and water [1]
In order to increase the activation energy of the system [5], some other variables, such as Proteins are usually employed in O/W emulsions due to their ability to reduce interfacial tension between oil and water, and to form films that act as a physical barrier, as well as prevent flocculation and coalescence of droplets [6]
Results showed that, according to response surface methodology (RSM) analysis and models, quadratic model was adequately fitted to optimize and predict the responses of droplet size and viscosity, but linear model was suggested for creaming index
Summary
Oil-in-water emulsions are systems that are composed of two immiscible liquids such as oil and water [1] They consist of small spherical oil droplets in an immiscible aqueous phase [2]. It is possible to form a kinetically stable (metastable) emulsion for a reasonable period of time by reducing their destabilization rate to adequately low level [4] by adding emulsifiers and/or thickening agents prior to homogenization [2]. In order to increase the activation energy of the system [5], some other variables, such as Proteins are usually employed in O/W emulsions due to their ability to reduce interfacial tension between oil and water, and to form films that act as a physical barrier, as well as prevent flocculation and coalescence of droplets [6]. Emulsifying and foaming properties are important properties of soy protein concentrates (SPC), and are useful in stabilizing emulsion systems
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