Are you thinking about producing your own freeze-dried food? Surely you also need to consider how to get the final product to the customer in perfect condition. Many retailers offer freeze-dried fruit with a 'crunchy' label, but often when you buy a packet of such fruit it is rather rubbery. Shelf life is also another factor. Why limit a product to a few months when the expiry date can be extended for years just by proper packaging.
How to keep your freeze-dried food from regaining moisture depends primarily on how you want to present your product. Should it last in its original state for a month or even years?
Oxygen absorber
This is a small bag that is thrown into a sealed bag with the food. It is probably the least effective way, but it is also the cheapest. Oxygen absorbers can work well if the goods go fast and you want to keep them crisp for a short period of time.
Due to the oxygen absorption, a higher proportion of nitrogen, as an inert gas, remains in the bag. This does not directly combat moisture, but rather the degradation of the food itself.
Silica gel
You've probably found a small bag with a balls in it at the groceries. This is silica gel, which is designed to draw moisture into itself. So the function is similar to an oxygen absorber, but this time we're trying to keep the food from getting moisture in a sealed or vacuum bag.
Silica gel is particularly suitable if you are not sure that all the contents of the package are well dried. Typically, for example, berries in their whole form - here you only need one or two blueberries that have been protected from freeze-drying by the peel and these can spoil the entire contents of the package. The silica gel can then absorb the moisture and extend the life of the packaged product.
Vacuum packaging
A lot of customers count on the cost of a vacuum sealing packer to start with. Somewhat surprisingly, I try to talk them out of this step, even though we use vacuum packing ourselves to test customer products.
We have feedback from our existing customers that they do not vacuum pack their food, but only in sealing bags (usually DoyPack) and only some of them add a silica gel bag or oxygen absorber. They offer their customers a 1 year shelf life and have never had a problem.
However, vacuum packaging may make sense if you plan to offer longer shelf life food or durable packaging, such as expedition food. In that case, you're not so much interested in the 'beauty' of the packaging as in its properties, and aluminium bags that don't let light in are also worth considering.
The downside of vacuum packing can be the crushing of fragile freeze-dried foods. So for maximum appearance and functionality at the same time, the most costly solution comes into play, namely a protective atmosphere.
Protective atmosphere
The principle is simple, the packer removes the air and replaces it with an inert gas, usually nitrogen or CO2. Food can then be packed into a box or bag without the risk of the food being crushed by the vacuum as in a poorly set vacuum packer. However, it is also the most expensive option in terms of cost.