What Is Spray Drying?

Spray drying is a method for systematic drying of materials. After the thin material is atomized in the drying chamber, in contact with the hot air, the moisture is rapidly vaporized to obtain a dried product. This method can directly dry the solution and emulsion into powder or granular products, and can eliminate the steps of evaporation and pulverization.

Through mechanical action, the material to be dried is dispersed into very fine particles like mist, (increasing the evaporation area of moisture, speeding up the drying process), and contacting hot air to remove most of the moisture in an instant, so that the solid in the material The material is dried to a powder.

(1) Pressure spray drying method:

Principle: Use

1. The parts in contact with the product must be easy to clean and sterilize;

2. There should be measures to prevent coke and prevent hot air from generating vortex and countercurrent;

3. Prevent air from carrying impurities into the product;

4. Equipped with temperature and pressure indicator recorder device, which is convenient for checking production operation;

5. Dust recovery device with high recovery rate;

6. The powder should be cooled quickly to improve the solubility and instant solubility;

7. Drying room temperature and exhaust temperature should not exceed 100 to ensure safety and quality;

8. The thick milk droplets are in uniform contact with the hot air during spraying to improve the thermal efficiency;

9. Minimize sticking to viscous substances.

Take the spray drying operation of soybean as an example:

Before spray drying, the soybean must be washed and peeled, and the non-protein components such as fat must be reduced, so that the most nutritious components in the soybean are concentrated, and the concentrated soybean can be spray-dried. The actual process of spray drying is divided into several steps: first, the liquid product is input into the atomizer, and a high-speed rotating wheel in the atomizer atomizes the liquid, so that the product becomes a state of fine particles mixed with solid and liquid.

In the second step, the atomized particles are directed into a controlled temperature and airflow drying chamber, and the hot air will evaporate the liquid in the particles. In order to make the final product meet the standards, the particles must be in contact with the hot air for the right time to maintain a certain amount of moisture in the powder. At the same time, the state of the drying chamber must be well controlled because the volume of the drying chamber and the air flow Will affect the nutrition of the product.

The third step is the last step in the whole process. The powder in the air stream is collected by a separator into a container, so that the final product can be packaged or mixed with other ingredients.

Fast drying speed. After centrifugal spraying of the material liquid, the surface area is greatly increased. In high-temperature air flow, 95% -98% of water can be evaporated in an instant, and the drying time is only a few seconds.

The co-current spray drying method can make the droplets flow in the same direction as the hot air. Although the temperature of the hot air is high, the hot air enters the drying room and immediately comes into contact with the spray droplets. The indoor temperature drops sharply, and the wet bulb temperature of the material is basically not It is also suitable for drying heat-sensitive materials. ^[1]

The nutritional content of some plants will be lost due to high temperature. For these plants, freeze-drying is an effective method of conserving. However, some plants do require a certain temperature to remove toxicity. For these plants, spray drying technology is It couldn't be more ideal. Taking soybean as an example, the concentration process requires a certain temperature to remove a substance called trypsin inhibitors (this substance will hinder digestion and break down proteins).

Spray drying is often the last step in the manufacturing process, which is to change the substance from liquid to powder through continuous spraying, mixing and drying. Among the many food storage technologies, spray drying has its unique advantages. Because the temperature used in this technology is not very high, it can effectively retain the taste, color and nutrition of food while removing microbial contamination. ^[2]

Spray drying has the characteristics of fast heat transfer, rapid evaporation of water, and short drying time. The product has good quality, crisp texture, and good dissolution performance. It can improve the dissolution rate of some preparations. It is suitable for heat-sensitive drugs. In addition, spray drying Can be used to prepare microcapsules.

Spray drying is commonly used to remove water from raw materials. In addition, it has many other uses, such as changing the size, shape or density of substances. It can assist in the addition of other ingredients in the production process and help produce products with the strictest quality standards.