You might not think your daily life involves emulsions unless you work in a scientific field. However, emulsions and the products of which they are a part are found in a variety of industries, from pharmaceuticals and food manufacturing to metal processing and more. For example, milk and butter are emulsions found in daily life, and emulsions are responsible for enhancing both the textural and visual properties of medicated creams.
So what exactly is an emulsion? Basically, it’s a mixture of oily and watery liquids. There are two primary kinds of emulsions: oil suspended in water (o/w) and water suspended in oil (w/o). Both are inherently unstable and require force and functional chemicals, otherwise known as emulsifiers, to break apart oil droplets in order to mix with watery liquid. Following are three main differences between o/w and w/o emulsions:
Suspended vs. continuous phase
Probably the most basic yet significant difference between o/w and w/o emulsions is which phase is suspended and which is continuous. Oil and water are normally immiscible, but a permanent mixture or emulsion can be achieved with the use of proper mixing and stability agents. In this case, smaller droplet sizes improve the effectiveness of either system, which may translate to increased bioavailability in pharmaceutical products or extended shelf-life in food/beverage products.
Type of product that can be created
O/w emulsions are the basis for water-based products; in the pharmaceutical industry, they can be found in creams like moisturizers and topical steroid products. W/o emulsions, though, form oil-based products such as sunscreen and many types of makeup.
Method used to achieve stability
All emulsions, whether w/o or o/w, require an emulsifier to assist with stability. O/w emulsions typically require more than one emulsifier, and they can be acquired separately or in a pre-mixed cocktail. In contrast, while w/o emulsions need one emulsifier, there are a limited number from which to select because the hydrophilic balance must be in a narrow range (3-6).
Again, due to the fact that water and oil are immiscible, powerful mixing is essential to conducting oil emulsification. Therefore, specialized machines such as high-pressure homogenizers, which work by forcing a sample through a narrow space and employing multiple forces, including turbulence and cavitation in addition to high pressure, are preferred. They not only impart high shear but also are able to reduce particle sizes much more efficiently than other blending and emulsification methods. In fact, high-pressure homogenizers can reduce droplet size to under one µm, produce more consistent emulsions and reduce creaming rate, thereby boosting the shelf-life of the emulsions.
Additional benefits of high-pressure homogenization for oil emulsification include production of stable emulsions, improved product consistency, shelf-life, texture, color and flavor and the ability to overcome the resistance caused by two immiscible liquids. Also, most high-pressure homogenizers currently manufactured offer reduced maintenance and reduced vibration and noise.
BEE International: Bringing the Benefits of Homogenization Straight to You
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