How to store freeze-dried food: mylar, jars and oxygen absorbers

Freeze drying takes the water out. Good storage keeps it out. Freeze-dried food left in the open air starts soaking up moisture within minutes, so how you pack it decides whether it lasts months or years.

What spoils freeze-dried food

• Moisture. The biggest one. Damp food goes chewy, then mouldy.
• Oxygen. It makes fats go rancid and flavours fade.
• Light and heat. Both speed up the loss of colour, flavour and nutrients.

Good packing deals with all three: an airtight, light-proof container, with the oxygen removed, kept somewhere cool and dark.

Option 1: mylar bags and oxygen absorbers (long term)

This is the standard for long storage. Mylar is a foil-lined bag that blocks light, air and moisture. An oxygen absorber is a small sachet that soaks up the oxygen left in the bag after you seal it.

1. Pack straight from the machine. Have your bags, absorbers and sealer ready before the cycle finishes.
2. Fill the bag, leaving a few centimetres at the top for a clean seal. Wipe any crumbs off the sealing area.
3. Add an oxygen absorber sized for the bag (see below), then seal straight away. Absorbers start working as soon as they hit the air.
4. Seal with heat. Use an impulse sealer or a clothes iron on a firm surface. The zip on resealable bags is for convenience after opening, not for long storage, so heat seal above it.
5. Label it with what's inside, the date, and how much water to add back if you know it.

Over the next day or so the bag pulls in slightly as the absorber takes up the oxygen. That's a good sign the seal is holding.

Which oxygen absorber size?

Absorbers are rated in cc of oxygen they take up. Bigger bags and airier food (whole strawberries, marshmallows) leave more air in the bag, so they need more. As a rough guide:

• 100 cc: small bags and jars
• 300 cc: medium bags, around 8 × 12 inches
• 1000 cc: large bags and buckets

When in doubt, go one size up or add a second absorber. Too much absorber does no harm; too little leaves oxygen in the bag. Keep unused absorbers in an airtight jar and use them quickly once the pack is open.

We stock 100 cc, 300 cc and 1000 cc absorbers, and heavy duty 7 mil mylar bags in small resealable, 8 × 12 inch and 10 × 14 inch sizes.

Option 2: glass jars (short term and everyday use)

Jars are handy for food you'll dip into often, like snacks, powders and ingredients for the week's cooking.

• Use clean, completely dry jars with good lids.
• Add a small oxygen absorber, or vacuum seal the jar if you have a jar sealer attachment.
• Keep jars in a dark cupboard. Clear glass lets light in, which fades colour and flavour over time.
• Plan to use jarred food within a few months, or sooner once you start opening it.

Option 3: food-grade buckets (bulk)

For bulk stores, pack food in mylar bags first, then put the sealed bags in a food-grade bucket with a tight lid. The bucket protects the bags from punctures and pests.

Where to keep it

• Cool: the cooler the better, and away from ovens, hot water systems and sunny walls. A hot shed in an Australian summer shortens shelf life.
• Dark: mylar handles this; jars need a cupboard.
• Dry and off the floor: away from damp, and out of reach of mice and insects.

How long does it last?

It depends on the food and how well it's packed. Harvest Right says properly packaged freeze-dried food can last up to 25 years. Fruit, vegetables and plain meals in sealed mylar with an absorber, kept cool and dark, last the longest. Foods with more fat, such as meat, cheese and egg, keep for a shorter time. Once a bag is opened, reseal it and use it within a few weeks.

Checking your stores

• The bag should still be tight or slightly pulled in. A puffy or loose bag may have a leak.
• Food should be crisp and dry. If it's chewy or clumped, it has taken on moisture: put it back in the freeze dryer for a few hours, or use it soon.
• Throw out anything that smells off, shows mould or has a damaged bag.

New to freeze drying? Start with our first batch guide.