Dehydration is the process of removing water from an entity, usually for the purpose of preventing spoilage by bacteria which are sustained by the presence of water, or for the purpose of decreasing the weight of an entity. Dehydration is typically accomplished by any of three methods:
Air-Drying is just that- allowing the material to dry in the most natural of ways, often with the aid of a heat source that when applied to the product, removes [most] of the water which comprises a great deal of most foods. This is the simplest and most cost-efficient method of dehydration. However, the heat involved in this process is likely to alter the natural characteristics of the food, as would any cooking process.
Freeze-Drying is an innovative, while more costly process by which the hydration in a food is frozen, and subsequently converted directly to gas form, without first becoming a liquid. This change is the process of sublimation, and is facilitated by altering the air pressure in the environment of the treated food. Skipping the liquid stage in the process of converting solid to gas avoids the change of properties that occurs in heat applied dehydration and cooking. Thus original properties of the solid are maintained, while having removed [almost] all hydration, creating lengthy shelf life and a fraction of the original weight. Simple reconstruction of the original form is accomplished by introducing a small amount of water
RayTM Pilot Plant Freeze Dryer by GEA
Spray-Drying is the process by which heat is applied to a sprayed liquid solution of the product to be dehydrated, and thereby, a powder is formed and the water is vaporized. This process is ideal for foods that are more water based than others, making air drying the solid a cumbersome process.
Sample Spray Drying Machine by MecKey® Machinery
Many products require sterilization treatment to lower or eliminate the level of unwanted microbiological substances that naturally develop. Any one of several methods may be employed to achieve this result, including:
-ETO (ethylene oxide)
Irradiation is the most common form of sterilization, especially in the US.
ETO is common in the case of spice products. It involves a chemical process that disrupts the reproduction of microbes.
Steam is seen as the safest method with minimal chemical or radiological residue. The sophistication of this method makes it the most costly, as well.
Do note, that a number of products are naturally sterile or low in microbes, and therefore do not require treatment. The levels of microbes that are deemed safe and acceptable depend on the particular intended application of the product as well as the government regulations in the place of production or marketing of the product.