25 Nov Freeze Drying – Best drying method

There are various types of drying for removing moisture from food. They are sun drying, hot air drying, solar drying and freeze drying. Freeze drying, also known as lyophilization, is a process that removes the moisture from food, preserving it for a longer shelf life while retaining most of its nutritional value and flavour.

This is one of the most expensive processes of drying but also the one that gives best results and the highest shelf life of products after drying.

The process involves three main steps: freezing, drying and packing.

The steps are

Freezing

Freshly cut fruits, vegetables or any other products are first loaded into trays and then put into blast freezers at -45 degree Celsius and this converts the products into ice crystals. This is a mandatory step before freeze drying.

Drying

After the completion of freezing process, material is transferred to a closed vacuum chamber. Here pressure and temperature are adjusted in such a way that the frozen ice goes directly from solid state to vapour (gas). This process is called sublimation. Because of this process, food retains it’s original shape, texture and flavour. Depending on the product, the temperature is sometimes raised at the end of the process to further remove moisture.

Packing

Material is taken out of the freeze dryer and then packed in a controlled atmosphere room with controlled temperature and Relative Humidity (RH) because packing the product in min oxygen is extremely important.

This is what a typical freeze dryer looks like

They can be manufactured in various sizes starting from 1 kg per batch upto 300 kg per batch and even more as per requirements.

Below is a photo of what freeze dried fruit looks like

Freeze Dried Strawberry

Freeze Dried Mango

Image source: (https://aumfresh.com/b2b-catalog/freeze-dried-mango/)

Advantages

• Higher shelf life
• Best texture, colour and flavour
• Preservation of nutritional value
• Extremely lightweight
• Versatile use of the process; not just in foods but pharma and chemical sector also

Freeze drying is the future in drying with many food processing companies expected to make the shift on it for best quality product outputs.