As a keen outdoors kinda guy, and a prepper, I often buy freeze-dried food when I go camping as its very convenient and light-weight. I was packing my rucksack for a weekend trek a few days ago, and I was looking through my collection of freeze-dried meals trying to decide what to take with me and I started wondering, how long does freeze-dried food actually last? I knew it could last many years but what is the shelf-life and how do you store it?
So, how long does freeze-dried food last? To answer this question I went and researched several manufacturers who sell freeze-dried food. They all gave ranges from around 10 to 30 years with 25 years seeming to be about the average. Its worth remembering that the shelf-life also depends on how you store the food. If for example, the seal is damaged on the food container or pouch, its likely to reduce the shelf-life significantly. Other conditions that can effect it are temperature fluctuations and humidity levels.
What is freeze-dried food?
The process of freeze drying food is known as Lyophilization. This is a type of food preparation where all the moisture has been removed to increase its shelf-life, while also increasing its flavour, texture and nutritional value by helping to preserve nutrients such as vitamins and minerals. In addition, freeze-dried food often contains fewer preservatives than canned or processed foods.
A special machine called a freeze dryer is used for the extraction of the water by first freezing the food to around -35 to -45 degrees celsius. Once frozen, the freeze dryer creates a vacuum in the food chamber. As the food is gradually warmed, the water crystals that form in the food are then converted to vapour using a process called sublimation.
When dry, the food is then ready to be placed in a vacuum sealed container that are both moisture and oxygen proof. This ensures that the food stays fresh until opened.
The whole process takes around 20 – 40 hours.
The resulting freeze-dried food is lightweight, easy to store, and can be rehydrated quickly by adding water. Freeze-dried food is commonly used in camping, backpacking, and emergency preparedness, as it can be stored for long periods of time without refrigeration and provides a source of nutritious food in a compact and convenient form.
Freeze-dried food is great as a convenient light-weight meal to take camping as a lot of the manufacturers store it in mylar bags. They usually sell larger portions in tins which are probably too bulky to take camping but would be great to store at home.
Freeze-dried food is very light due to the fact that all of its moisture has been removed. To prepare the food for consumption, all you need to do is add boiling water to the bag, wait for a few minutes for the water to rehydrate it and you end up with an instant meal.
Unfortunately the cost of these dryers is usually too high for the average person to justify. The average cost of ready-made freeze-dried meals is also usually a lot higher than other forms of preserved food.
Some common examples of freeze-dried foods include fruits, vegetables, meats, soups, and desserts but you can freeze-dry any food and even whole meals. What better way to store excess food than popping it into the freeze dryer. Maybe you’ve made a few big apple pies, just split it into meal size portions along with a helping of custard and freeze-dry it all.
How do you store freeze-dried food?
Freeze dried food is usually supplied in sealed containers or pouches. Each pouch usually holds a single meal with the containers or tins holding 8 or more portions.
Its advisable to keep the food in a cool, dry place with low humidity such as a food pantry or basement whilst avoiding any fluctuations in temperature.
How do you use freeze-dried food?
Due to the fact that freeze-dried food has had all of its water removed, the preparation of the the food simply involves opening the sealed pack and adding water (typically hot water) back into the food and letting it soak in for a few minutes for it to rehydrate (although some foods may take a lot longer). The amount of water varies depending on the type of food so you should read the instructions on the pack.
The food will be ready to eat once the texture of the rehydrated food resembles the same as freshly cooked food of the same type.
Once the food is rehydrated, you can either eat it as it is or even combine it on a camping stove along with other foods.
Do you remember space ice-cream?
In the 1960’s, space ice-cream, also known as freeze-dried ice-cream, was developed for the Apollo space missions. It was created to provide the astronauts with a sweet, non-perishable treat to eat while they were in space.
Once dried, the ice-cream turned very brittle but it had the benefit that it could be kept at room temperature for long periods. If you fancy trying it, you can even still buy it at some museums and science centres.
How much do freeze dryers cost?
I didn’t spend a huge amount of time looking into the cost of a typical freeze dryer as I’m not intending to buy one (yet), but from a quick glance, the majority of them would have to be shipped in from the USA. I had a similar problem when I was looking for a pressure canner a couple of years. The model I wanted (An All American 925 25 Quart) had to be imported so I had to pay the extra delivery charge on top of its price.
A popular make of freeze dryer is a brand called Harvest Right. There are four main models and the one you choose would depend on how much food you intend to process. Some figures for the small, medium and large are below:
Small – Starting At: £2395
Food Per Batch: 1.8 – 3.2 kg
Freeze Dried: 1 – 1.5 gal
Medium – Starting At: £2895
Food Per Batch: 3.2 – 4.5 kg
Freeze Dried: 1.5 – 2.5 gal
Large – Starting At: £3595
Food Per Batch: 5.4 – 7.2 kg
Freeze Dried: 2 – 3.5 gal
I’ll write another article about buying a freeze-dryer when I’m actually going to buy one but I imagine I’ll go for the Medium Harvest Right. There are addons that you can also buy with the Harvest Right models such as an oil-free pump which could increase the price by another £1000. This replaces the standard oil-based pump.
How much does it cost to make your own freeze-dried food?
This section is a rough estimation based on the figures supplied by Harvest Right plus the information I’ve looked at on the pack of a typical freeze-dried meal (a 100g pack of macaroni cheese from Fuel Your Preparation).
Lets assume you have purchased a medium freeze-dryer from Harvest Right and you want to make as much macaroni cheese as you can in one batch. This dryer can take 3.2 – 4.5 kg of food and will have a running cost of £1.00 – £2.30 a day.
The pack of the macaroni cheese is 100g in weight and requires 155ml (155g) of water to rehydrate it giving it a total weight of 255g. I’ve come up with the following estimates:
I will assume 48 hours running time to make the maths simple and the higher electricity cost of £2.30 a day. I will also assume that you can only get 3.2kg of macaroni cheese into the dryer:
Electricity: £4.60
Running Time: 48 hours
Food Per Batch: 3.2kg
Weight of one pack of macaroni cheese before being freeze-dried: 255g
If we divide the amount of macaroni cheese that we have started with by one serving of 255g, we get:
Total packs of macaroni cheese: 12
So for the cost of £4.60 (plus the cost of the food of course), you can make around 12 servings. That is a lot cheaper than buying them from a company which will be around £84. Although it is cheaper to buy the food in larger tins than individual packets, it still works out a lot cheaper to make your own.
Once I’ve bought my own dryer, I’ll write another article with better estimates and add in the initial cost of the food ingredients.
How does freeze drying compare to other preservation methods?
If you compare the typical shelf-life of freeze dried-foods with other common preservation methods such as canning and dehydrating, you can see that freeze-dried food lasts for a lot longer:
But with great shelf life, comes great cost. And as mentioned above, its the price. A pouch of freeze-dried beans will cost in the region of £5 – £7. Now compare that to a regular tin of baked beans, 50p? That’s a huge difference in cost.
I’ll write another post in the future about the cost of several preservation methods and it will be interesting to figure out what the electricity costs are going to be. From looking at the Harvest Right website, they indicate that typical running costs for the small and medium dryer are around £1.00 – £2.30 a day and the large around £1.60 – £2.50.
I have owned a dehydrator for many years but there are several big differences between freeze-dried and dehydrated food apart from cost and shelf-life. Freeze-dried food has had 99% of its water content removed, whereas dehydrated only has 90%. The less water content remaining in food decreases the chances of microbes and bacteria growing which allows the food to last longer before becoming spoiled (hence the increase its shelf-life of freeze-dried food).
Not all foods can be dehydrated and also, the freeze drying process retains more nutrients in the food when compared to dehydrating. Freeze-dried food also has better taste and texture.
Of course, just because a meal is freeze-dried, it doesn’t mean its necessarily healthy. Check the ingredients on the packet as some manufacturers may add preservatives and other chemicals or excess sugar just like so many other commercial foods.
For me personally, when I’m out walking or camping, the convenience of the light-weight of freeze-dried food far outweighs its cost and the shelf-life is great for emergency food storage, but I must admit, most of the supplies I store at home are a combination of dehydrated and canned food with a small amount of freeze-dried. So, I wont be throwing my tins of baked beans just yet.
Now, if only I owned a freeze dryer… watch this space.