Abstract
AbstractAtomization of emulsions with pressure swirl atomizers is a common task in food process engineering. Especially in spray drying processes for food materials like dairy products, it is the technology of choice. During atomization, emulsions are subjected to high stresses, which can lead to deformation and breakup of the dispersed droplets. In this study, the influence of atomization pressure (5–20 MPa) and initial oil droplet size (0.26, 3.1, and 20.8 μm) on the oil droplet breakup during atomization of food based oil‐in‐water emulsions with pressure swirl atomizers was investigated. It was shown that a significant oil droplet breakup takes place upon atomization. The size of oil droplets with an initial value of 3.1 and 20 μm was reduced up to 0.36 μm. No breakup of oil droplets with an initial value of 0.26 μm was observed. The breakup was highly dependent on the atomization pressure. The results were analyzed based on existing knowledge on droplet breakup in laminar flow. A concept to estimate capillary numbers during atomization was developed based on common models from different applications. The results of this study can be used to control the resulting oil droplet size after atomization with pressure swirl atomizers.Practical applicationSpray drying of emulsions is a widely used process in the food industry to produce products with encapsulated oily components. Product examples include infant formula, milk powder, and the encapsulation of aroma and coloring compounds. Breakup of the oil droplets during the atomization step of spray drying can change a previously adjusted and desired oil droplet size. As the oil droplet size in the final product can be responsible for several properties like sensorial aspects and stability, a control of oil droplet breakup is essential. Pressure swirl atomizers are widely used in industrial applications as atomization devices. In this study, oil droplet breakup during atomization with these atomizers was investigated. The findings in this study allow a better control of the oil droplet size during atomization in practical applications.
Highlights
Spray drying of emulsions is a common task in food engineering for the production of products with encapsulated oily components
The results correspond to atomized emulsions with an initial Sauter mean diameter (SMDi) of 3.1 and 20.8 μm
The experimental study of atomization of O/W emulsions with pressure swirl atomizers showed that a significant oil droplet breakup takes place during atomization
Summary
Spray drying of emulsions is a common task in food engineering for the production of products with encapsulated oily components. Typical examples include products such as coffee creamers, infant formula, and the encapsulation of active ingredients, aroma, and coloring compounds (Reineccius, 2004). The process of spray drying starts with the atomization, by which the liquid emulsion is dispersed into small spray droplets. These droplets are subsequently dried to powder by contact with a hot air stream. Pressure swirl nozzles are widely used as atomization devices in the food industry (Barbosa-Cánovas et al, 2005). The oil droplets should be encapsulated in a matrix material, which acts like a barrier, providing protection against oxidation or losses
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