Electrostatic Spray Drying of High Oil Load Emulsions and Heat Sensitive Materials

Spraying Systems Co Pty Ltd
By Bogdan Zisu, Spraying Systems, Fluid Air, Melbourne, Australia
Wednesday, 01 September, 2021


Preservation of biological material is often achieved by removing free water and lowering water activity. In commercial settings, this is predominantly possible by using established technologies such as high-heat spray drying and low-temperature freeze drying. Both are effective; however, each technique is also limited to specific applications.

Spray drying for example operates at high temperatures and is unsuitable for drying biologically active material susceptible to thermal degradation. Living cells, microorganisms and many active ingredients often result in denaturation, product degradation and loss of quality when heated above specific temperatures. The commercially viable alternative to high-heat spray drying is sub-zero freeze drying. Although the technology is well established in the preservation of microbiological samples and other biological materials, the operating temperatures are so low that they cause damage to some materials. The underlying limitation of commercial freeze drying is generally not temperature related but rather batch processing, thereby limiting throughput.

There is a clear need for continuous, non-batch commercial-scale drying technologies that maintain a product’s thermal integrity. This gap in process capability was recently filled by the PolarDry® range of electrostatic spray dryers. By delivering an electrostatic charge during the atomisation process of liquid droplets, water is evaporated at lower temperatures than possible in traditional high-heat spray drying. Electrostatic spray drying is an innovative approach combining gas-liquid atomisation and electrostatic charge. Heat transfer to the atomised droplets is based on latent heat transfer, allowing powders to be dried at temperatures as low as 30°C.

Scanning electron microimage showing lactoferrin powder produced with the PolarDry electrostatic spray dryer.

Successful applications include the drying of biological solutions such as colostrum and lactoferrin where there is no loss in biological activity. Other suitable applications include the drying of microalgae and living microorganisms. Probiotic microorganisms, agricultural bacteria and various other species associated with the human microbiome have been dried successfully using a polysaccharide carrier to obtain >50% bio-mass to dry-mass ratio. Survival post-drying is generally high with expected viable losses of approximately half a log reduction.

Unlike traditional high-heat spray drying, electrostatic spray drying takes place in an inert gas environment where oxygen is replaced by nitrogen. This expands applicability to oxygen sensitive materials and not only appeals to anaerobic microorganisms, but it is extremely well suited to spray drying of encapsulated oils. By electrostatic charging the active components base on polarity, the surface chemistry of the atomised droplets changes during the drying process and this becomes evident in resulting powders. In powders with high fat content, some of the surface fat is replaced by protein and carbohydrate. When using a carbohydrate carrier and protein stabiliser, oil retention in the powder reaches 60–80% (w/w). Interest in oil encapsulation is driven by the processing of highly volatile and unsaturated lipids, oil soluble flavour and aroma compounds, nutritional formulations and cannabinoid oils.

Scanning electron microimage of encapsulated oil powder containing 50% oil produced with the PolarDry electrostatic spray dryer.

The future of food and nutraceutical manufacturing is driven by innovation, and high value-adding nutritional, functional and bioactive ingredients are key to sustainability. Consequently, the drive for high-quality ingredients also requires innovation in manufacturing technology necessary to support emerging markets and novel product development. PolarDry electrostatic spray dryers are developed to meet the demands and challenges associated with conventional spray- and freeze drying by providing alternative commercial solutions.

Designed and built in the US, the PolarDry commercial range of spray dryers was first launched in the US followed by Europe and Asia where sales have steadily grown in the years following market launch. Fluid Air Australia and New Zealand is excited to introduce the innovative PolarDry technology to the region with the support of a state-of-the-art, fit-for-purpose research and development ISO certified facility located in Melbourne, Australia. Equipped with advanced analytical and electrostatic spray drying capability, the facility exists to support local manufacturers with R&D requirements.

Fluid Air analytical equipment in the Melbourne laboratory testing facility.

For more information visit the Fluid Air website: https://bit.ly/3jLaMbw.

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