What is a desiccant and how does it work?

The United States military has conducted much of the best research on the use of desiccants in packaging, and it has largely set the standards by which they are judged. Desiccants have a variety of uses including domestic storage of food items. Each type of desiccant has particular physical and chemical characteristics that may need to be considered in relation to what you propose to do with them and humidity and temperature ranges where it performs best.

What is a desiccant?

It is a substance with very hygroscopic properties, which promotes drying by soaking up moisture or water vapor from the air surrounding it. Desiccant for food storage should be chemically inert or stable. The most commonly used desiccants are Silica gel, montmorillonite clay, and molecular sieves.

How does it work?

The primary cause of moisture damage in food storage is the simple fact that warm air can hold more moisture than cold air. Moisture gets into the storage vessel from the outside or by evaporation from the food item. When the temperature in the storage vessel changes damaging moisture conditions arise. To solve this problem, the air inside the storage vessel must be kept dry. Desiccants control the moisture level in storage vessels like containers, crates, boxes, etc.

Desiccant for food storage

In food storage, the main problem in every package is fighting moisture damage and odors of the product. Desiccants absorb moisture and fight any bad odors to preserve the product. Water vapor or moisture causes the product form molds, to be contaminated with fungi and bacteria, and to corrode. Moisture and condensation also often causes odor. These occurrences may greatly affect the quality and eventually lead to food spoilage or product damage. The most applicable standard for domestic food storage is a desiccant that will adsorb at least 6 grams of moisture or water vapor at 40 per cent relative humidity at 77 degrees F or 25 degrees C. To store food safely, one should find desiccant packs that are recommended to be used with foods safely as not all types of desiccant packs are suitable for food storage.

Types of desiccants

The most commonly used desiccants are those that employ silica gel as the main agent. There are also desiccants that use clay and others that use different chemicals.

Silica GelDessicant: Silica Gel Sample

Silica Gel desiccants are the ones very often found on different food and pharmaceutical products. Silica Gel is also the only desiccant approved for direct contact with food and pharmaceutical products by the Food and Drug Administration. Silica gel is a naturally occurring mineral called silicon dioxide, SiO2. It is purified and processed and made available in beaded or granular form. Silica gel packets can reduce the relative humidity from 90 per cent RH down to 40 per cent RH, and performs best at room temperature. It absorbs water vapor or moisture at high temperatures up to 220 degrees F or 105 degrees C. Silica gel has a vast range of pore sizes, and this makes it capable of absorbing not only water but other compounds such as ammonia, aromatics olefins, and alcohol. Silica gel has the ability hold up to 30 per cent of its weight in water, and it can be recharged and reused by sticking it in an oven to dry.

 

Activated CharcoalDessicant: Activated Charcoal

This is a great desiccant because of its immense network of tiny pores. Activated charcoal has the ability to absorb not only water but unpleasant scents, toxins, and pollutants. It can be used as a desiccation around the house but also in medicine and agriculture.

 

Indicating Silica GelDessicant: Indicating Silica Gel

Indicating silica gel is comparable to the normal silica gel desiccant, and the difference is that it is not chemically stable or inert, and has color changing ability to indicate the amount of water vapor or moisture it has absorbed. It has a deep blue or orange color when dry, and it will change color as the moisture content rises, eventually turning into pink or black when saturated indicating it is time to be replaced. It must be noted that Indicating Silica Gel has cobalt chloride, and maximum care must be taken to ensure that it does not come into contact with pharmaceuticals, food, or other consumption items.

In food storage, the main problem is fighting moisture damage and odors of the product. Desiccants absorb moisture or water vapor and fight any bad odors to preserve the product. To store food safely, one should find desiccant packs that are recommended to be used with foods safely as not all types of desiccant packs are suitable for food storage. Look for Silica gel desiccant packs for foods that are FDA approved, and use them to store food and pharmaceuticals products including grains, dried foods, etc.