Abstract
Emulsifiers are added to enhance product stability to obtain a satisfactory shelf-life. For this reason, stable emulsions that do not form peroxides nor change the fatty acid composition of food, as well as safe treatments to obtain them, are aspects of utmost importance. High-pressure homogenization is a conventional approach to prepare emulsions because of its high efficiency. In addition, the beneficial effects of ultrasound on the processing efficiency are known. Therefore, the impact of high-pressure homogenization (30 MPa, 50M Pa) or ultrasound power (270 W) on the emulsion stability and emulsifying properties of 5% coconut oil-in-water emulsion were discussed in this study. The complexes (3:7and 4:6, by weight) of propylene glycol alginate and xanthan gum were selected as emulsifier. The apparent viscosity, particle size and distribution, emulsifying properties and ζ–potential of 5% coconut oil-in-water emulsion before and after ultrasound treatment or high-pressure homogenization were investigated and compared. The micro structure of the emulsion was observed under the fluorescence microscope. The experimental results showed that both high-pressure homogenization and ultrasonic treatment effectively reduced the apparent viscosity, average droplet size and narrowed the distribution range of the emulsion, compared with the pre-emulsion. However, aggregation in the emulsion appeared only after being subjected to high-pressure homogenization, while the emulsion made by the ultrasound treatment remained stable during 30 days storage. In conclusion, this study provides valuable information regarding emulsion preparation methods that can be feasible in food and beverage industries, demonstrating a better performance of ultrasound in optimizing and extending food shelf-life in food and beverage industries.
Highlights
Oil-in-water emulsions are conventionally defined as a thermodynamically unstable systems which include two immiscible liquids, in which oil is distributed into the water[1]
Oil-in-water emulsion stability compared with water (23.46 mN/m) at oil-water interfaces, because propylene glycol alginate (PGA) combination with XG resulted in a mixture containing both hydrophilic bonds and hydrophobic bonds, which can be effectively adsorbed at the interface of oil-water
The average droplet size of 5% coconut oil-in-water emulsions prepared by 270W ultrasound treatment was smallest compared to that prepared by other ultrasound intensities.(S1 and S2 Figs)
Summary
Oil-in-water emulsions are conventionally defined as a thermodynamically unstable systems which include two immiscible liquids (generally water and oil), in which oil is distributed into the water[1]. Oil-in-water emulsion stability coalescence, flocculation or Ostwald ripening[2]. The stability of emulsions is the most important parameters for the shelf life of the food products[3]. The preparation method is great influencing on the stability of o/w emulsion. Some ways were used to prepare emulsions such as mechanical, ultrasound (US) treatment and high-pressure homogenization
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