Drying Heat-Sensitive Food Products
Maintaining high product quality during the drying operation is the foremost concern in food drying applications. The dryer design should minimize product discoloration (toasting effect). Likewise, the type of dryer selected should preserve the product flavor, aroma, and efficacy. To satisfy these demands, the optimal dryer design should address the following three criteria.
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Time and Temperature Exposure:
Loss of product quality is typically a result of the combined effect of exposure time and drying temperature. A longer residence time dryer requires lower temperature operation, while a shorter residence time dryer allows for higher temperature heat input.
Particle Exposure to Heat:
Individual particle contact with the heat source (air stream or vessel wall) allows for good moisture-stripping ability and more efficient processing, minimizing risk of degradation.
Narrow Residence Times:
Strict control over residence time provides consistent operation, avoiding temperature gradients across particle masses. Drying operations with assured plug flow operation provide consistent treatment and evaporation.
Designing and reviewing food drying systems, with respect to achieving all these desirable features to maintain high product quality, is just one of our specialties. Bepex has long served in the development of continuous drying processes for heat-sensitive materials. With seven unique proprietary drying technologies, we can test, design, and offer a more precise match for your application, rather than forcing your application into a single drying technology.
When approached with drying applications for heat-sensitive materials, Bepex typically begins our review with two of our seven thermal technologies. Our first option is a relatively new innovation, our PCX Flash Dryer. Our PCX is typically utilized in drying high-moisture organic materials in difficult to handle forms, such as wet/filter cakes, pastes, and slurries. The PCX is a mechanical flash dryer, using heated air streams and rotating dispersion plates to generate a thin layer of material. This thin layer provides intimate contact between the particles to be dried and the heated gas stream. The rotating dispersion plates generate intense agitation, exposing additional surface area for more efficient heat transfer. Material residence time inside the dryer itself is short, at an average of 2-3 seconds. Once discharged from the dryer, material is pneumatically conveyed to separation components, typically a cyclone followed by a baghouse. During this conveyance period, the moisture-laden air provides evaporative cooling of the dried product, quickly lowering material temperature to avoid degradation or color change that occurs with extended time and temperature exposure. The PCX Flash Dryer provides an economical and compact alternative to spray dryers and ring dryers, without sacrificing product quality.
If energy cost or emissions control are of primary concern, our Solidaire Paddle Dryer provides an attractive alternative to flash drying. The Solidaire vessel walls are jacketed, typically designed for the use of steam or hot thermal oil. The rotating adjustable paddle rotor disperses material into a thin working layer along the heated vessel walls, which provides conductive heating to carry out evaporation. A heated gas stream (often inert) typically runs counter-current to material flow, picking up evaporated moisture and carrying it to a condenser for collection. Since the purge gas is not used as the primary heat source, the quantity of gas required is minimized, providing for more efficient operation and lower operating utility requirements.
No matter your drying requirements, Bepex is unique in our ability to fully suit your application with an appropriate technology, rather than trying to fit your technology into a single drying product. Our Process Development Center provides the ability to test, generate market-ready product, and provide proof of concept for your process prior to scaling to commercial capacities. Whether drying vegetable protein, starch, yeast, or another temperature-sensitive material, Bepex has the experience, products, and capability to serve as a valued partner in your product and process development.
Visit our recently updated website, www.bepex.com, to learn more about these and other products and process operations.