Modern nutrition research has found that tomatoes have high nutritional value, low calorie content, antioxidant properties, and anti-cancer properties; It can remove freckles, beautify, prevent aging, and lose weight. Tomato powder is suitable for both internal and external use, with the function of "beautifying". It is suitable for low-fat meals, weight loss, and beauty. It is worth mentioning that tomatoes contain lycopene, which is a powerful antioxidant that helps delay aging and can withstand stress. And it can balance water and oil secretion. With a slight change in tomato powder, you can make different facial mask for cleansing, repairing, spot removing and whitening.

So how do tomatoes go from being turned into powder? Today, the editor will lead everyone to explore the drying process of tomatoes.

There are many drying methods for tomatoes, including freeze drying, expansion drying, drum drying, foam layer drying and spray drying.

(1) Freeze drying method
This method uses low temperature to freeze tomato concentrate, and then sublimates the water under high vacuum to dry it. The obtained tomatoes still retain their original structure without damaging their original shape and size. Therefore, freeze-dried particles have a porous structure, retaining the space originally occupied by moisture without collapsing, which is beneficial for the rapid rehydration of the product. However, this method consumes a lot of energy and the freeze-drying equipment is very expensive, resulting in high product costs.
(2) Puffing drying method
The puffing drying method uses puffing drying equipment to dry tomato concentrate. Usually, a pressure of 2.6 millimeters of mercury is required for dehydration, and the temperature of tomato concentrate is usually 60-70 ℃. In order to achieve a moisture content of 3% in the final product, the drying time is usually 90 minutes to 5 hours. Before removing the vacuum, the product should be cooled down to avoid collapse of the fluffy structure, as the resulting tomato powder is thermoplastic; The tomato powder prepared by this method has a relatively hard structure, with a volume similar to that of the concentrate, and poor rehydration performance of the product. In addition, puffing must be carried out under vacuum conditions, which is relatively expensive, resulting in a higher product price.
(3) Spray drying
Before spray drying, tomato concentrated slurry should be homogenized. The homogenization pressure is generally 150-200 kilograms per square centimeter. Generally, centrifugal or two fluid spray dryers with cooling jackets on the tower wall (double tower walls, air can be used to cool the temperature of the drying chamber wall) are used for drying; If the heating medium is pre dehumidified dry air, the inlet air temperature during drying is generally around 150-160 ℃, the outlet air temperature is 77-85 ℃, and the feed concentration is generally 20% -30%.
There are some modified spray drying equipment on the market that can be used to process fruit and vegetable powder. Some use air as a drying gas and adopt a medium inlet air temperature of 75-95 ℃ for drying, which can improve production speed; Others use dehydrated air as a drying gas and dry it at lower inlet temperatures (25-50 ℃). So this method is the * choice for drying tomatoes.
(4) Foam layer drying method
The key of this drying method is to form stable foam by adding foaming substances such as soybean protein, globulin, fatty acid fat, sugar fat and monostearate glyceride into tomato concentrate. The gas temperature inside the dryer is approximately 93 ℃, and the speed is about 100-130 meters per second, added in a countercurrent manner. The drying time depends on the characteristics of the product and the drying conditions used, generally ranging from 15 to 18 minutes.
(5) Drum drying method

The speed of the drum is generally 3.5 revolutions per minute, the vapor pressure is 3.5 kilograms per square centimeter, and the spacing between the drums is 0.2 millimeters. In order to quickly remove the water vapor generated during drying, air needs to be introduced, and the airflow is opposite to the direction of rotation of the drum, that is, it flows in reverse; And control the humidity of the air in the material collection area to be 15% to 20%. However, this drying method cannot truly achieve the purpose of drying tomato powder. Because the obtained product has a moisture content of at least 7%, it needs to be further air dried at 20 ℃ for more than 24 hours. Otherwise, products with a moisture content of over 7% will experience a significant decrease in color, flavor, and nutritional value during storage.

Principle of tomato spray drying:
System working principle: Air is filtered and heated before entering the top air distributor of the dryer, and the hot air enters the drying chamber uniformly in a spiral shape. The feed liquid passes through the high-speed centrifugal atomizer on the top of the tower body, and (rotating) spray into extremely fine mist like liquid beads, which can be dried into finished products in a very short time in parallel with hot air. The finished product is continuously output from the bottom of the drying tower and the cyclone separator, and the exhaust gas is discharged by the fan.
Working principle of atomizer: When the feed liquid is fed into the feed tube of the atomizer, it is quickly distributed once or twice and sent to the high-speed rotating atomizing disc. Due to the centrifugal force, the feed liquid extends into a thin film on the surface of the rotating atomizing disc and moves towards the edge of the disc at an increasing speed. When it leaves the edge of the disc, the feed liquid is atomized, with droplet, filamentous, and film like splits. The type of split is mainly determined by the speed, feed amount, properties of the feed liquid, and the shape and diameter of the atomizing disc. The size of the droplets mainly depends on the circumferential velocity of the atomizing disc.

Characteristics of tomato spray drying:

The drying speed is fast, and the surface area of the material liquid is greatly increased after being atomized by a high-speed centrifugal atomizer. In the hot air flow, 95% -98% of the water can be evaporated instantly, and the drying time is only a few seconds. It is particularly suitable for drying heat sensitive materials.
The product has good uniformity, fluidity, and solubility, high purity, and good quality. The production process is simplified and the operation control is convenient. For liquids with a moisture content of 40-60% (up to 90% for special materials), they can be dried into powder products in one go without the need for crushing and screening, reducing production processes and improving product purity. The particle size, bulk density, and moisture content of the product can be adjusted within a certain range by changing the operating conditions, making control and management very convenient.

Shanghai Qiaofeng focuses on the research and production of powder equipment, and is a powder drying equipment expert by your side.