Drying, dehidration, lyophilization     Play Audio
Module 3, Unit 5, Level: Advanced

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Drying, dehydration, lyophilization, food preservation



Drying, dehidration, lyophilization
Drying and dehydration are food preservation methods that require the application of heat to remove moisture. Freeze drying is a preservation method that requires the application of cold to remove moisture.

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Drying and dehydration aim to inhibit microbial activity and reduce enzymatic activity. These methods aim to increase the shelf life of food products, facilitate storage due to the smaller volume, and preserve the color and natural aromas. Additionally, they can be applied without adding preservatives or sugars.

Certain previously dried or dehydrated products can be hydrated once again to be consumed in their original state, such as beans and chickpeas.

The benefits of freeze drying include simplification of the aseptic environment, greater stability of dry powder such as coffee or milk, removal of water without excessive heating of the product, as well as the absence of chemical alteration of substances susceptible to deterioration by heat or loss of volatile constituents. Lyophilization also provides greater resistance to the spread of microorganisms.

The three methods increase the options for the consumer, ensuring that out-of-season products, such as dehydrated mushrooms, maintain their quality. Furthermore, they may also represent a way to reduce food waste.
Representative Products
Drying: fruit (plums, apples, dates and grapes), pulses (peas, broad beans and lentils), spices (rosemary and parsley), fish (cod).
Dehydration: fruit (apple, pineapple, persimmon, strawberry and mango), gelatin.
Freeze drying: fruit (passion fruit, kiwi fruit, pineapple and apple), vegetables (carrots, broccoli and tomatoes), seafood (shrimp), mushrooms, milk and coffee.
In the preparation of food through drying, dehydration and freeze-drying methods, the quality of the package and its storage are critical factors in maintaining a low level of moisture to avoid contamination of the product by microorganisms.

Temperature control is essential to determine the final product characteristics (taste, odor, texture, color), based, for example, on the loss of volatile compounds, protein denaturation, or formation of hardened layers on the surface.
Further references
- Bennamoun L, Li J. Drying Process of Food: Fundamental Aspects and Mathematical Modeling. Natural and Artificial Flavoring Agents and Food Dyes. 2018; 29–82. doi:10.1016/b978-0-12-811518-3.00002-8
- FDA [Internet]. Lyophilization of Parenteral (7/93): Guide To Inspections Of Lyophilization Of Parenterals. 2014 [citado 2021 Mar 15].
- Chen XD, Mujumbar AS. Drying Technologies in Food Processing. Blackwell. 2008.

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