Which principle is used in freeze-drying?
sublimation
The fundamental principle in freeze-drying is sublimation, the shift from a solid directly into a gas. Just like evaporation, sublimation occurs when a molecule gains enough energy to break free from the molecules around it.
What is freeze-drying equipment?
Freeze-dryers are regularly designed with four basic components: a drying chamber, a vacuum pump, a heat source, and a condenser (Figure 2). The correct selection and operation of these components are critical to reach the benefits of the lyophilization process and depend on the requirements of each product.
How do freeze-drying machines work?
Raw or cooked foods are placed in the freeze dryer where they are frozen to between -30 degrees and -50 degrees Fahrenheit. Once frozen, the freeze dryer creates a vacuum in the food chamber. 3. As the food is gradually warmed, the water turns to vapor and evaporates out of the food (sublimation).
What is the principle of freeze?
When a liquid is cooled, the molecules’ total energy reduces. At any point, the volume of heat removed is high enough to pull the molecules tightly together through the enticing forces between molecules, and the liquid freezes to a solid.
What are the steps of freeze-drying?
There are three stages in the process: freezing, sublimation drying, and desorption drying. The freezing phase is the most critical in the entire freeze-drying process. It is important to freeze foods rapidly in order to avoid the formation of large ice crystals, which deteriorate the final product quality.
What is the purpose of freeze-drying?
Freeze-drying, or lyophilization, removes moisture from raw, frozen product through a vacuum system and process called sublimation. Frozen raw product is cut down to the desired piece size and spread evenly onto trays that are stacked and stored in freezers.
What are the advantages of freeze drying?
Freeze-drying retains nutritional value better than other drying methods, further supporting consumers’ desire for nutrition from whole foods. The process also preserves the actual color and shape of the original raw material, reassuring consumers they are actually getting real fruits and vegetables in their diets.
What is lyophilization principle?
Lyophilizers work by freezing the material, then reducing the pressure and adding heat to allow the frozen water in the material to sublimate.
What are the steps of freeze drying?
Why is freeze drying important?
The primary purpose of freeze drying within the food industry is to extend the shelf-life of the food while maintaining the quality. Freeze-drying is known to result in the highest quality of foods amongst all drying techniques because structural integrity is maintained along with preservation of flavors.
What is the principle of drying?
The IICRC has found that there are four principles to properly drying a structure: removal of standing water, evaporation through air movement, dehumidification and temperature control.
What is the freeze dry process?
Freeze-drying is the process by which the solvent (usually water) and/or suspension medium is crystallized at low temperature and removed by sublimation. Sublimation is the direct transition of water from solid state to gaseous state without melting.
What are the working principles of freeze drying?
The main part of the oven , a condenser , refrigeration units , pumps, heating / cooling devices . Its working principle is to be freeze -dried items to the triple point temperature, and then the articles under vacuum solid water ( ice ) sublimate directly into water vapor , are excluded from the article, the article dry.
What are the components of a freeze dryer?
The main components of freeze drying equipment are: The refrigeration system cools the (ice) condenser located inside the freeze dryer. The refrigeration system can also be employed to cool shelves in the product chamber for the freezing of the product.
What should the system pressure be for freeze drying?
PRESSURE & TEMPERATURE DURING PRIMARY DRYING. A general guideline is to choose a system pressure that is 20% to 30% of the vapor pressure of ice at the target product temperature. When the vacuum level set point is deeper than the vapor pressure of ice at the current product temperature, sublimation can take place.
What is the purpose of a condenser in freeze drying?
The purpose of the condenser is to attract the vapors being sublimed off of the product. Because the condenser is maintained at a lower energy level relative to the product ice, the vapors condense and turn back into solid form (ice) in the condenser.