# Powdered Foods: Structure, Processing, and Challenges: A Review
## 3 Powdered Food Production Processes
### Spray-Drying  
The spray-drying process comprises transforming a liquid substance into a powder by releasing droplets into a hot convective medium. These droplets are released via an atomizer, facilitating the evaporation process in the drying chamber and generating powdered products. This process has several technological applications, such as the production of instant food powders, pharmaceuticals, food additives, and the encapsulation of bioactive compounds [21; 22; 23].  
This method has the advantages of being a low-cost process, adaptable to industrial scale, forming almost spherical particles, suitable for both thermosensitive and thermoresistant products, and providing good stability of the final products. Regarding its limitations, the product must have a low viscosity, and the drying process is less effective for large droplet fractions due to the short process time, in addition to necessitating high energy consumption and having problems regarding food oxidation [22; 24; 25].  
Different authors have evaluated spray- and freeze-drying in different food matrices. For example, [PERSON] et al. [26] assessed the stability of strawberry flavor, comparing different drying methods, including spray- and freeze-drying. Despite lower moisture content in the spray-drying method, the freeze-drying process exhibited higher yield values.  
Figure 2: Spray-drying (**left**) and freeze-drying (**right**) processes.  
In general, the spray-drying technique showed greater stability concerning temperature and exhibited better morphological characteristics such as spherical and smooth particles [26].  
To facilitate the spray-drying process, substances known as drying carriers or encapsulating agents are employed. These drying carriers act as protective barriers for substances that will be encapsulated, ensuring greater stability for compounds sensitive to light, humidity, oxygen, and heat [27].  
The choice of the drying carrier material depends on the purpose for which the powdered food will be used. Drying carriers can impart new properties to the powder, such as changes in solubility and viscosity. Using the right material can also decrease undesirable effects for powdered foods, such as the stickiness effect [28].  
For honey and other foods with a high sugar concentration in their composition, the use of maltodextrin and gum arabic can be viable alternatives, reducing the high hygroscopicity of powdered foods, consequently minimizing stickiness effects due to their high molecular weight and glass transition temperature (Tg) [29].  
The concept of glass transition is defined by the change in state from an amorphous solid to a rubbery state. This concept is important, as many foods that are turned into powders enter an amorphous state after the drying process [4]. Unlike crystalline structures, in the amorphous state, the solvent will penetrate the solid and, due to the glass transition, the amorphous material will migrate to the water on the surface of the powder, significantly increasing its viscosity. This viscoelasticity depends on the deformation rate of the material, temperature, and moisture content of the powdered food [30].