Ultrasonic Nano-Emulsification for Microencapsulation before Spray-Drying
- In order to microencapsulate active ingredients via spray-drying, a fine-sized stable micro- or nanoemulsion must be prepared.
- Ultrasonic emulsification is a facile and reliable technique to produce stable micro- and nano-emulsions
- As alternative surfactant, biopolymers such gum arabi or WPI can be used in ultrasonic emulsification processes as food-grade stabilizers.
Emulsions and emulsion quality play a significant role regarding efficiency and stability of oily microparticles prepared via encapsulation processes such as spray drying. Emulsion stability, viscosity, droplet size and oil/water ratio are crucial factors. During the processing, which starts with the preparation of the emulsion and ends with the spray-drying, all those physical and chemical properties of the emulsion must be maintained, in order to prevent a deterioration of the microparticles. The quality of microencapsulation and emulsions stability are closely related and influence the quality of the final powdered products final significantly. Therefore, a reliable emulsification technique is required. Ultrasonic emulsification is a well established technology, which is used in various industries worldwide to produce macro-, nano-, and micro-emulsions.
High-performance ultrasonicators are well established for emulsification processes in the food, pharma and cosmetic industry. The application of intense ultrasound waves is an efficient method to produce emulsions with micron- or nano-sized droplets. Ultrasonic emulsification is based on the principle of cavitation, in which high intensity ultrasound waves and its high velocity liquid jets shear the droplets’ surface, creating thereby small droplets and stable emulsions.
Ultrasonic emulsions can be stabilized using conventional emulsifying agents (e.g. polysorbate, sorbitan etc.), but also using biopolymers (e.g. guar gum, gum arabic, WPI etc.). Industries have recognized the huge potential of biopolymers as emulsion stabilizers. Especially for food, pharmaceutical and cosmetic emulsions, biopolymers allow for the development of products with a “clean” label. Biopolymers and biopolymer complexes are available in large volumes and of food-grade quality. Biopolymer complexes (such as polysaccharide-protein complexes) are superior to biopolymers since they offer improved properties than each polymer on its own. A biopolymer composed of a protein and a polysaccharide (= complex carbohydrate polymers) offers the benefits of each molecule. The protein increases the surface activity so that a higher surface layer saturation at a significantly lower concentration is obtained. The polysaccharide in the complex reduces the interfacial tension and thus the energy that is required to generate new surfaces. Thereby, polysaccharides enhance the formation of small droplets. A biopolymer complex offers the best of its both component and makes therefore a strong stabilizer.
High Performance Ultrasonicators
Hielscher’s high-performance ultrasonic processors are installed worldwide for the preparation of stable macro-, nano- and microemulsions. With a product portfolio ranging from small handheld ultrasonic lab devices to high-power industrial ultrasonic systems for the commercial production of large inline streams of emulsions, Hielscher Ultrasonics offers you the most suitable ultrasonicator for your process.
Power input, amplitude (displacement at the sonotrode), temperature, and flow rate can be adjusted to the requirements of your formulation. Our industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available.
Precise control over the sonication parameters and automatic data recording on an built-in SD-card ensure high processing quality and allow for process standardisation. All our ultrasonic processors are designed for the 24/7 operation under full load. Robustness, low maintenance and user-friendliness are further advantages of Hielscher’s ultrasonicators, which makes them your work-horse in production.
Accessories such as Hielscher’s unique MultiPhaseCavitator, a flow cell insert that injects the second phase via cannulas directly into the cavitational hot-spot (see pic. left), help to setup an optimal ultrasonic emulsification system.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
|Batch Volume||Flow Rate||Recommended Devices|
|1 to 500mL||10 to 200mL/min||UP100H|
|10 to 2000mL||20 to 400mL/min||UP200Ht, UP400St|
|0.1 to 20L||0.2 to 4L/min||UIP2000hdT|
|10 to 100L||2 to 10L/min||UIP4000hdT|
|n.a.||10 to 100L/min||UIP16000|
|n.a.||larger||cluster of UIP16000|
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Literature / References
- Campelo, Pedro Henrique; Junqueira, Luciana Affonso; de Resende, Jaime Vilela; Domingues Zacarias, Rosana; de Barros Fernandes, Regiane Victória; Alvarenga Botrel, Diego; Vilela Borges, Soraia (2017): Stability of lime essential oil emulsion prepared using biopolymers and ultrasound treatment. International Journal of Food Properties Vol.20, No.S1, 2017. 564-579.
- Maphosa, Yvonne; Jideani, Victoria A. (2018): Factors Affecting the Stability of Emulsions Stabilised by Biopolymers. In: Science and Technology Behind Nanoemulsions (Edited by Selcan Karakuş). 2018
Facts Worth Knowing
Biopolymers as Emulsion Stabilizers
Stabilizers and surfactants are required for most emulsions to make them long-term stable. Biopolymers such as polysaccharides and proteins are widely employed as functional ingredients in emulsion systems. Biopolymers are a natural type of emulsifying agent, which offer a good emulsion stabilizing performance due to their gelling and emulsifying capacity. Since the production of stable emulsions is a prerequisite for a successful encapsulation via spray-drying of food products, biopolymers are a preferred type of stabilizer. Biopolymers can be employed as stabilisers on their own or in combination.
Biopolymers such as gum arabic and whey protein isolate (WPI) are inexpensive and can be easily processed in food production. Gum arabic is a mixture of anionic carbohydrates and some proteins. Its highly branched proteins, that are closely linked to the polysaccharide structure, give gum arabic good emulsifying properties. Whey protein isolate is composed from a mixture of globular proteins. Those globular proteins can be quickly adsorbed onto the oil droplets surface during homogenization, which facilitates the formation of small droplets.
Other common biopolymers used as emulsifying agents are gelatin, xanthan gum, starch, casein, pectins, maltodextrin, ovalbumin, sodium alginate, and carboxymethylcellulose amongst others.
Biopolymer complexes are composed of two or more biopolymers. Biopolymer complexes can be synthesized by chemical, enzymatic or thermal treatments. The complexation generally increases the robustness and solubility of the final biopolymer complex, enhancing their usability and stability. Especially the resulting higher stability in regards to varying temperatures, pH and ionic strength are important factors for emulsification processes.