Freeze drying, also known as lyophilization, is widely regarded as a superior industrial drying and preservation method. By drying at lower pressure, boiling points are lowered which allows products to dried at lower temperatures compared to other methods. This reduces damage to the product and ensures cellular integrity is retained.
Perhaps the key benefit of freeze drying is that all cellular integrity is retained throughout the drying process. The only thing removed from the product is water. This means that products retain the following characteristics from when they’re fresh to when they’re dry:
Other benefits include the fact that vitamins and enzymes remain intact, shipping weight is significantly reduced and the product life is preserved, providing suitable packaging is used. Reconstitution (rehydration) is almost instantaneous when water is added to the dried product.
General steps to successful freeze drying are as follows:
Moisture is ‘locked’ into the product by freezing in a separate freezer.
NB: Difficult products can be frozen inside the Freeze Dryer. Shelf freezing reducesthe shelf temperature in the chamber to -18°C or lower, but this adds to the processing time.
2. LoadProduct is placed into a chamber, which is evacuated to low pressure. As a guide, atmospheric (sea level) pressure is 1017mBar, and the chamber is evacuated to around 1mBar before drying begins.
3. DryEnergy is then gradually applied to the product over a period of 20-24 hours, although this varies depending on the product and loading. This heat (energy) causes the ice to sublimate – that is transform from ice to vapour without passing through the liquid phase. The water vapour is then attracted to the lower temperature ice coil where it condenses as ice.
Product is removed and packed in air tight sealed bags to prevent rehydration
- Strictly speaking, anything can be freeze dried providing it contains water. Freeze drying is often used for food preservation and also for storing biologicals and pharmaceutical products. Examples include:
- Vegetables, meat and fish
- Fruits and juices
- Aloe Vera, Echinacea, and nutraceuticals
- Cultures for use in the dairy industry
- Water damaged books and documents
- Viruses and bacteria storage
To find out more about freeze drying and our range, check out our web site – www.cuddonfreezedry.com
We have a free guide to help you choose a freeze dry. To download this click our link.