The method of freeze-drying is one of the feasible options for the long term storage of food. The process of freeze-drying involves flexibility to preserve any vegetables or fruits and remove moisture content. The brands of best-canned food for long term storage is packed with freeze-drying. In addition, freeze-drying food has the ability to:
- Produce nutritious and whole-food ingredients with high prolonged shelf life.
- Making food products accessible, versatile and convenient.
- Helps to keep the actual shape and colour of the raw material for a long time.
What is Freeze Drying?
Freeze-drying is a technique that includes vacuuming a completely frozen sample to remove any solvents or water, allowing the ice to transition directly from solid to vapour without passing through a liquid phase. Because of the long-term preservation features, it provides to the sample’s biological and chemical structure, this process, known as sublimation, and the low heat input required, it is excellent. Lyophilization can be done in a variety of sizes, from small at-home freeze dryers to big, industrial-scale machines.
Stages of Freeze Drying
There are three stages of the freeze-drying process such as pre-drying, primary drying and secondary drying.
Pre-Drying:
The most crucial stage of the freeze-drying process is the pre-freezing stage. At this point, the sample material must be cooled to at least the melting point of that particular sample. This ensures that the sample is thoroughly frozen and ready for sublimation. Evaporation will occur if the sample is not frozen solid, and the sample will not obtain the same preservation qualities as sublimation.
The size of the ice crystals that develop is affected by the rate at which your sample freezes. It can affect the speed of reconstitution, the length of the freeze-drying process, and the stability and integrity of your sample if done incorrectly.
Because water molecules can travel more easily out of the sample during sublimation, larger ice crystals allow for more efficient and faster freeze-drying. Large crystals can rupture the cell walls of food or tissue samples, causing harm to the sample. In these cases, it’s recommended to freeze quickly using flash freezing, which produces smaller ice crystals.
Primary Drying:
When you turn on your freeze dryer and vacuum pump, the primary drying process begins. Evaporative cooling of the sample begins in the low-pressure environment, allowing energy in the form of heat to speed up the freeze-drying process. Approximately 93 per cent of the water in the sample is sublimated out at the end of primary drying. Depending on the sample type and heat input, this stage can take several days. Primary drying is where the run would end for laboratories that use their freeze-drying equipment for sample preparation and resuspension. The run would go on to secondary drying in order to preserve the meat in a can for a long time.
Secondary Drying:
Water molecules attached to the sample are released during the secondary drying process. In this stage, further heat is applied to drive off surplus moisture, leaving a moisture content of roughly 2%. Secondary drying is most commonly utilised in the preparation of samples for long-term preservation and storage.
The freeze-drying process makes the food the best-canned food for a long time.