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rom milk to chocolate: how Ramsden emulsions are changing the food industr
In the food industry, the stability of emulsions is crucial to improving the quality and market value of products. Ramsden emulsions, also known as Pickering emulsions, have significantly revolutionized the production and formulation of many food products through the use of solid particles. This article will explore the properties of Ramsden emulsions and their important applications in the food industry.
The concept of Ramsden emulsions dates back to 1903, when Walter Ramsden first observed the phenomenon and S.U. Pickering further described the emulsion form in 1907.
The special feature of Ramsden emulsions is that they are able to better stabilize mixtures of water and oil, which is achieved by adding solid particles. These particles can adsorb at the water-oil interface, thereby preventing the coalescence of small oil droplets, which can further improve the stability of the emulsion. Such emulsions can be in the form of oil-in-water or water-in-oil, but more complex systems such as water-in-water and oil-in-oil emulsions also exist.
Studies have shown that particle properties, such as hydrophobicity, shape, size, as well as the electrolyte concentration of the continuous phase and the volume ratio of the two phases, can affect the stability of the emulsion.
When oil and water are mixed, without the addition of any stabilizer, the oil droplets will merge on their own due to the reduction in energy. However, when we add solid particles, they adsorb to the interface and avoid this merging process. The contact angle characteristics of these particles reflect their hydrophobicity. If the contact angle of the particle is low, the particle will be mostly wetted by the droplet, making it difficult to prevent the merging of the droplets. In practical applications, the stability is optimal when the contact angle is about 90°.
In the food industry, the most common form of Ramsden emulsion is the water-in-oil emulsion, since most organic particles are hydrophilic. For example, homogenized milk is a Ramsden-stable emulsion whose milk proteins (casein) are able to adsorb on the surface of milk fat globules and act as surfactants, thus replacing the milk fat globule membranes that are damaged during the homogenization process. . In addition to milk, products such as low-fat chocolate, salad dressings and margarine can also use Ramsden emulsions in their formulations to improve stability.
With increasing attention to environmental, health and cost issues, research into Ramsden emulsions has advanced rapidly, especially in the past 20 years.
Over time, the researchers discovered that synthetic nanoparticles, whose size and composition could be precisely controlled, could serve as stabilizers for Ramsden emulsions. However, recently, natural organic particles have also gained increasing attention due to their breakthroughs in cost-effectiveness and biodegradability, and they are derived from renewable resources. The findings suggest greener options for food manufacturing.
In addition, Ramsden emulsions excel in applications such as oil and gas stimulation and water treatment. Certain Ramsden emulsions even remain stable under gastric conditions and show resistance to abnormal gastric lipolysis, which makes them potentially useful in oral delivery systems and for enhancing satiety.
It is worth noting that the use of amphiphilic "Janus particles", particles that are hydrophobic on one side and hydrophilic on the other, also helps improve the stability of Ramsden emulsions.
These Janus particles have a higher adsorption energy on the liquid-liquid interface, thereby enhancing the overall stability of the emulsion. Likewise, latex particles can be Ramsden stabilized and ultimately form a permeable shell or capsule, which is called a colloidal shell. The droplets of Ramsden emulsions are also suitable as templates for microcapsules, forming water-impermeable capsules. In addition, this form of entrapment can also be applied to water-in-water emulsions (i.e., dispersions of phase-separated aqueous polymer solutions), and the process may also be reversible. Even so, Ramsden's stable microbubbles also have good application prospects in ultrasound contrast agents.
With further research and application of Ramsden emulsion, its impact on the food industry will only become more profound. What direction will food manufacturing develop in the future?
