# Powdered Foods: Structure, Processing, and Challenges: A Review
## 7 Powdered Products: Case Studies
### Dairy Products  
The dairy industry stands as one of the most consolidated food industries in the world, with dairy products representing one of the largest fractions of powdered foods on the market. This category includes whole and skimmed milk powder, concentrated and isolated milk protein, isolated and concentrated whey protein, caseins, and more. Powdered dairy products are also used in confectionery, bakery, infant formulas, meat products, and even the pharmaceutical industry (44). Milk, as an emulsion in a dispersed system (oil-in-water), is a complex food due to its mixture of components (macronutrients, minerals, vitamins, and water) (71). Therefore, the application of heat in the drying process can induce physicochemical changes in milk, resulting in loss of nutrients (e.g., water-soluble vitamins), such as a decrease in the quality \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Food Product** & **Particle Size** & **Powder Process** & **Powder Characteristics** & **Rehydration Characteristics** & **References** \\ \hline \multicolumn{5}{c}{Dairy products} \\ \hline Skim milk & 14-20 \(\upmu\)m & Spray-drying & Very bright, low color saturation, irregular and rough surface & Non-wettable, hardly dispersible, fairly soluble & [64] \\  & & & Smooth and dimpled & Greater wettability, dispersibility and solubility \\   Milk protein concentrate & 18.9–57.3 \(\upmu\)m & Spray-drying & powders with high protein content & for powders with lower protein content & [65] \\  & & & Fair porosity, spherical particles, and not very hygroscopic & Low wettability and solubility & [66] \\  & & & Particle size and amount of surface fat & Greater rehydration power & \\   Cheese & 42.0–86.1 \(\upmu\)m & Spray-drying & are dependent on the formulation & for young cheeses and faster dispersibility for old cheeses & [66; 67] \\ \hline \multicolumn{5}{c}{Fruit and vegetable products} \\ \hline Blueberry juice & - & Spray-drying & Shrunken and smooth spheres, low moisture content, and bright color & High solubility, lower dehydration time when compared to foam-mat freeze-drying & [68] \\  & & & Spherical shapes, high hygroscopicity, and dented surface & High dispersibility, wettability, and solubility & [69] \\   Sugarcane juice & 1.84 \(\upmu\)m & Spray-drying & hygroscopicity, and dented surface & & \\  & & & Color similar to the raw & \\  & & & Pulp, presence of starch granules and viscous characteristics & High wettability and solubility & [50] \\   Mango pulp & 267.95 \(\upmu\)m & Freeze-drying & Crunchier texture, rounded and porous powder with the increase of natural fibers & Viscous and worse wettability with the increase of natural fibers & \\  & & & Large porosities and skeletal-like structures & Low solubility, wettability, and rehydration power when compared to larger particles & [49] \\  & & & Smooth, porous, and spongy structure & High rehydration rate & [33] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Food powders and rehydration parameters. of powdered products [44]. For instance, [PERSON] et al. [66] highlighted that the conditions of the spray-drying process are essential to improve the survival of lactic acid bacteria in yoghurt and its sensory acceptance. [PERSON] et al. [64] explored different air outlet temperatures in the spray-drying process for skim milk, achieving a product with high yields and low water activity. As for rehydration properties, regardless of the temperature degree, skimmed milk powder was soluble, but was nonwettable and hardly dispersible [64]. On the other hand, [PERSON] et al. [65] investigated the physical and rehydration properties of concentrated milk protein, obtaining particles with high viscosity content with increasing protein content, such as a smooth surface. The concentrated protein showed good instant properties in samples that had a lower protein concentration [65]. Lastly, [PERSON] et al.