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.


The secret to keeping stored food fresh

Perishable items keep longer when not exposed to oxygen

Oxygen may be essential to life, but here the kicker – it can totally devastate your food supply. That may sound like a very strange statement, but as a scientist, it was one of the first priorities I dealt with when I started to set up my “prepper storage unit.” There is no big mystery as to how oxygen makes your food spoil and why you should eliminate it. Oxygen, which is abundant in the air around us, can carry particles and deposit them in our food, it can also chemically react with food. The trick is to learn how to store food correctly and cut down on the amount of oxygen in the immediate environment.


Oxygen and food

We seldom leave food out because we are concerned that flies and bugs will spoil our food. But, if it isn’t the flies, what is it that spoils the food? Don’t worry about the bugs so much, worry about the oxygen. Let’s take a look at what happens to that apple you left out a few days ago. Certain enzymes in the apple react with the oxygen and make it soft. If you live in a warm climate, the apple with spoil quicker as heat speeds up the reaction. Come to think of it; this is another reason why  is such a threat to our food.

 Oxygen is also needed by mold, yeast, and bacteria. There is always some mold present in most foods that we buy, but we should do our utmost to protect the food. If we give oxygen free access to our food, you will even find that the dry pasta, rice, and flour you are storing, will be infected by mold or yeast. It will spoil the food, and if we were to eat it, we could become ill from food poisoning.


Mold and other contaminants require oxygen to spread and grow

Stop the access

So, you have been out to by your first lot of food for your prepper store room. That is great, but before you went out to spend all of that money on food. Did you remember to check out some storage containers? It is a bit of a chicken and egg situation, but it is a good idea to invest in good quality storage containers first. This gives you a chance to layout your storage, and you are then fully prepared when you bring the food home. Now, you can put away the food safely.

But, don’t only invest in good quality storage containers. Do a little bit of research and find out how important oxygen absorbers and desiccants are to good food storage. People that work with food stuffs on an everyday basis always recommend the use of desiccants and products which absorb oxygen as well. They know the most common food stuffs are easily affected by oxygen, and that these products are just as important as the storage units themselves.

Oxygen absorbers are self-explanatory, but what are desiccants? Simply put, they are driers, and you may have come across them in the form of silica gel. This is often what you will find in a small bag or pouch inside a bottle of vitamins. It helps to keep the contents dry and fresh.

dessicants protect food

Oxygen and water

Oxygen can introduce airborne contaminants to water as well. The good news is that if you want to store water safely, you can use things like Mylar bags. I use large 55-gallon bags to store water during the summer. It helps us out a lot as sometimes we get our water cut off due to water shortages. The water stays fresh, and the system seems to work very well. You can also invest in many different types of waters filters which can be a good alternative if you have stored the water for some time.

If you are not concerned about getting access to water, you should try using a water filter anyway. You will find the water will taste better, and during a disaster, a water filter may be really important if you have to fetch water from a stream or river.

These are some of the simplest and best ways to deal with what I call “food pollution.” How oxygen will find ways to spoil food will always amaze me. To eliminate the problem of food spoilage, you really need to be a step ahead of those oxygen particles.