Freeze drying of food

Freeze-drying presents an excellent method for long-term food storage. It involves employing lyophilization, a process that lowers the product's temperature below freezing, followed by the application of a high-pressure vacuum to extract water as vapor. This procedure directly transitions water from its solid state (ice) to vapor, bypassing the liquid phase, while desorbing water from the "dry" layer.

The freeze-drying process consists of three stages:

*Freezing the product, typically done under atmospheric pressure.
*Primary drying, also known as proper freeze-drying, which involves the sublimation of frozen free water. This step is usually carried out under reduced pressure.
*Secondary drying, referred to as desorption drying, which focuses on drying the products to achieve the desired humidity by eliminating the remaining bound water.

Freeze-drying finds extensive application in preserving high-quality food, biological materials, and pharmaceuticals, such as proteins, vaccines, bacteria, and mammal cells. Rapid freezing during the process is crucial to prevent the formation of large ice crystals that could negatively impact the final product's quality. In the primary drying phase, pressure is reduced through the application of a high vacuum, while heat is supplied to facilitate the ice's sublimation.

Freeze-drying stands out as one of the most effective methods for preserving the activity of beneficial plant compounds, like phytochemicals, and nutrients, while maintaining the color, flavor, and structure of the food. Freeze-dried foods exhibit superior quality compared to those dehydrated by alternative techniques. They have a longer shelf life and are lighter in weight than dehydrated counterparts. Furthermore, freeze-dried food retains its color and shape more effectively than dehydrated food, owing to the absence of a liquid phase and the low temperature involved in the process.
Freeze drying of food

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