Using Silica Gel Sachets With Stored Food

Yes, you can use silica gel sachets in mylar bags alongside oxygen absorbers, and the bag sizes sold for food storage are listed as compatible with both.

The two products do different jobs. Silica gel absorbs moisture, and an oxygen absorber removes oxygen. Used together, with a sachet sized to the bag, they give a dry, low-oxygen environment for rice, pasta, oats, pulses and other dry staples.

What follows is how to choose the sachet, how to use it safely, how to tell when one is spent and how to bring it back into service.

Silica gel and oxygen absorbers do different jobs

It helps to be clear about what each product is for, because they are often sold side by side and are easy to confuse.

Silica gel is a desiccant. Its purpose, in the supplier's words, is to "remove all the moisture which could impact the longevity of your food storage, creating the perfect dry environment for your storage and protection needs"⁵. Moisture inside a sealed bag is what turns dry rice soft, clumps powdered milk and gives mould a foothold. A desiccant takes that moisture out of the air in the headspace of the bag.

An oxygen absorber does something else: it removes oxygen. Mylar bags sold for food storage are commonly described in terms of the oxygen absorber they suit, and the supplier states that foods sealed in mylar bags with oxygen absorbers can last for decades⁵. The bag listings pair each bag size with a specific absorber, from 50cc for the smallest ziplock bags up to 2000cc for the largest heavy duty bags⁶.

Neither product substitutes for the other. A bag with an absorber but no desiccant still contains moisture; a bag with a desiccant but no absorber still contains oxygen. The bag listings treat them as a pair, which is the simplest guide to follow.

Using both in one bag

The bag listings are explicit that the two can go in together. The 12cm x 20cm standup bag takes a 100cc absorber and a 10g sachet⁹.

Larger bags follow the same pattern. The 25cm x 35cm heavy duty bag, the 25cm x 40cm ziplock heavy duty bag and the 25cm x 35cm standup bag are each listed for a 300cc absorber and a 60g sachet¹⁰. The 35cm x 50cm heavy duty bag is listed for a 2000cc absorber and a 100g sachet¹².

In practice:

1. Fill the bag with dry food, leaving enough headspace to seal.
2. Add the oxygen absorber sized for the bag.
3. Add the silica gel sachet sized for the bag.
4. Seal the bag, pressing out as much air as you reasonably can first.
5. Label the bag with its contents and the date.

The supplier's own guidance for long-term storage is to use airtight mylar bags with oxygen absorbers, to seal them with a steam iron with the steam off or a hair straightening iron, and to label each bag with contents and date¹³. If you have no heat sealer, there are other ways to close a bag; see how to seal mylar bags without a heat sealer.

Which sachet size for which bag

The sachet has to be big enough for the volume of air it is drying. Too small a sachet in a large bag will be spent long before the food is, and the food will slowly pick up moisture. The supplier publishes a size guide for each sachet, and the bag listings repeat it.

The sachet listings give the same advice from the other direction. The 60g sachets are described as ideal for 25cm x 35cm, 24cm x 34cm and 25cm x 40cm bags⁴. The 100g sachets are described as ideal for 35cm x 50cm, 48cm x 74cm and heavy duty 48cm x 74cm bags¹.

The smallest bags suit small quantities of light, moisture-sensitive foods. The 20cm x 25cm bag is suggested for small amounts of rice and pasta, cereals, oats and grains, nuts and pulses, and dehydrated meat and vegetables¹⁵. For the bigger picture on what to put in them, see rice, pasta, oats and pulses for long-term storage.

Keeping sachets dry before use and telling when they are spent

A desiccant works by absorbing moisture, and it does not wait until it is in your bag. A sachet left open in a kitchen cupboard, a shed or a garage will take in moisture from the air around it and be part-used before it ever reaches your food.

Keep sachets in their original sealed packaging until the moment you need them. The 60g sachets come in packs of 1, 5, 10, 50, 100 and 250⁴, and the 100g sachets in packs of 1, 5, 10, 50, 100 and 160¹.

Some sachets carry a colour indicator. The supplier states that the indicator material in its desiccant packs is well suited to repeated regeneration and reuse⁴. When the indicator shows the sachet has taken up moisture, it can be dried out and used again.

Reusing silica gel sachets

Silica gel is reusable, and the supplier says so plainly: its desiccant sachets are well suited to repeated regeneration and reuse⁵. The 60g sachets are described as easily regenerated in an oven or microwave, with the instruction to gently heat the sachets until the colour returns, after which they can be reused⁴.

That is the maker's instruction for its own product, and it is the one to follow. A few practical points sit around it:

• Regenerate only sachets that are intact. A torn sachet will spill beads into your oven or microwave.
• Let sachets cool and dry before they go back into a food bag.
• Regenerate in a batch, so you always have dry sachets ready when you fill bags.
• Keep regenerated sachets sealed until use, exactly as you would new ones.

The 60g sachets are described as completely non-toxic for food storage and as conforming to UK, EU and US FDA regulations for food safety⁴. The 100g sachets are described as completely non-toxic for food storage¹. The 30g sachets use iron salts as the additive².

Buying sachets on their own or in a bundle

You can buy the pieces separately or together. Mylar bags are sold on their own, and the bag listings state which absorber and which sachet suit them¹⁷. They are also sold as bundles with oxygen absorbers, and the bundle listings repeat the sachet size².

Buying the bundle removes the commonest mistake, which is putting too small a sachet in a large bag. If you buy separately, work from the sachet's own size guide rather than from memory⁴.

For the wider picture on bags, absorbers and how long food keeps in them, see mylar bags and oxygen absorbers for dry stores and how long food lasts in mylar bags with oxygen absorbers. If you are still deciding between bags and jars, mylar bags or glass jars for dry food sets the two side by side. And before you fill anything, keeping a long-term store cool, dry and free of pests covers where the bags should live once they are sealed.