Spray-dried foods can be divided into two categories: non-sticky and sticky. Non-sticky food materials are easy to spray dry. The design of the simple dryer and the final powder can flow freely. Examples of non-sticky materials include powdered eggs, powdered milk, solutions and other maltodextrins, gums, and proteins. In the case of viscous foods, there is a drying problem under normal spray drying conditions. Sticky foods usually stick to the walls of the dryer, or they may become useless and condense in the drying chamber and conveying system, causing operational problems and low product yields. Examples of viscous foods include foods rich in sugar and acid.
Stickiness is a phenomenon encountered during the drying process of often spraying food materials rich in sugar and acid. Powder viscosity is a cohesive adhesion characteristic. It can explain particle-particle viscosity and particle-wall viscosity. The measure of strength combined with powder particles is due to its internal characteristic called cohesion, which forms lumps on the powder bed. Therefore, the force required to penetrate the powder agglomerates should be greater than the cohesive force. Adhesion is an interfacial property, and the powder particles adhere to the tendency of the spray drying equipment wall. The cohesion and adhesion are the key parameters for designing drying and drying conditions. The surface composition of powder particles is mainly responsible for stickiness. The cohesive force and adhesion tendency of the surface material of the powder particles are different. Drying requires a large amount of solute to be transferred to the surface of the particle, so it is in bulk. The cohesion between particles is the formation of fixed liquid bridges, moving liquid bridges, mechanical linkage between molecules and electrostatic gravity and solid bridges. The main reason for the adhesion of powder particles on the walls of the drying room is the loss of materials in the spray-dried sugar and acid-rich foods. When the silty remains longer, it will dry on the wall and lose it.
Control viscosity: Material science and process-based methods to reduce viscosity problems. The basic methods of materials science include high-molecular-weight material liquid drying aids to increase the temperature other than the glass transition, and the process methods include the scraper and bottom of the machine room.
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