Tomato powder preparation by spray drying

Optimizing the spray drying process for preparing tomato powder is of great significance. The inlet hot air temperature is a key factor affecting the moisture content of the tomato powder. As the inlet hot air temperature increases, the moisture content of the tomato powder gradually decreases, but this downward trend weakens after the temperature exceeds 140°C. When the inlet hot air temperature is too low, a large amount of powder adheres to the inside of the spray tower, resulting in a moisture content exceeding 9%, which fails to meet the requirements for powder preservation. Conversely, when the temperature is too high, exceeding 180°C, the powder darkens in color, develops a burnt smell, and heat-sensitive substances decompose and are lost, leading to a deterioration in the quality of the tomato powder. Therefore, a suitable inlet hot air temperature range is crucial.

The dry matter content of the material also has a significant impact on the spray drying process. When the dry matter content is 8%, severe adhesion to the walls of the spray tower occurs, resulting in high powder moisture content and poor quality. A dry matter content of 20% indicates poor material flowability, easily clogging the nozzles, and is unsuitable for spray drying. In contrast, materials with a dry matter content of 12% exhibited good process adaptability, producing powders with better color and quality after drying, and a moisture content of 6.7%.

Controlling the material temperature is equally important. Below 50°C, the temperature difference between the inlet and outlet is small, resulting in low drying efficiency and a slow drying speed. Above 65°C, nutrients (such as heat-sensitive vitamin C and lycopene) are severely lost, and the pink color darkens. Therefore, the material should be kept at around 55°C for optimal results.

Flow rate and centrifugal spray dryer speed are also key parameters affecting the quality of tomato powder. A flow rate of 10 ml/min and an atomizer speed of 28,000 r/min result in minimal wall adhesion, good atomization, and high-quality tomato powder. During spraying, maintaining a constant centrifugal spray dryer speed is crucial; too high or too low a flow rate will affect production efficiency and powder quality. Excessive flow rate may lead to poor atomization and wall adhesion, while insufficient flow rate will reduce production efficiency.

In summary, by optimizing process parameters such as inlet hot air temperature, dry matter content of the material, material temperature, flow rate, and centrifugal spray dryer speed, the quality and efficiency of tomato powder prepared by spray drying can be effectively improved.