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How to use Aluminium-laminated bags

Aluminium laminated bags are perfectly suited as hermetical containers for long-term storage, as already explained in "What determines the shelf life of staple foods?". Combined with the oxygen absorbers they provide an oxygen-free space.

Using the slideshow below we are illustrating how 20 kg of wheat are prepared for long-term storage using aluminium laminated bags and oxygen absorbers.

The slideshow should answer any emerging questions. To begin with, I would like to briefly go into heat-sealing aluminium bond bags. After all, this is the deciding factor in the use of aluminium laminated bags.
Heat-sealing - or 'sealing' - causes the two inner surfaces of the bag facing at the opening to fuse, makes it hermetically tight after filling and in principle can be accomplished through three different methods:




Impulse Sealer
These sealers actuate only when depressed, but do so with an extremely high electric output (e.g. 1000W). This will make the Teflon covered wire glow within seconds
No preheating, extremely effective and very easy to handle
relatively high wear (wire and Teflon require regular replacement), due to their size most impulse sealers can only be used for bags up to a certain width (only one open side). Requires some practice or the bag will easily be overheated

Portable Sealer
These sealers use a lower electric output (e.g. 50W), therefore require initial warm-up like with a press iron. In general provides the option to heat only one side or both sides.
Suitable for any bag size, easy to handle, in general no wear, also available with furrows.
Compared to the impulse sealer requires hard pressing (unless the suitable attachment for foot operation is available)

Press Iron
A standard press iron may in fact also be used. However, this requires a suitable pad for the sealed seam, e.g. a square tube (see slideshow). In this case set the press iron to the highest setting.
No additional expenses, suitable for any size, no wear.
This requires some practice, is also more cumbersome and takes longer.

When using one of these devices, be sure the machine's sealed seam width is 5 mm or more. This will ensure a very sturdy seam. The device should also be suitable for laminates (i.e. also for aluminium laminated film). I personally prefer the hand-held heat tongs, specifically the model Futura Cello (150C) with two furrowed sealing jaws and 1 cm sealed seam width (see slideshow).

The following sealing shows how to use a hand-held heat sealer as well as a standard press iron.


Measure moisture content

First ensure the wheat to be preserved is sufficiently dried. I use a hygrometer for this purpose which displays the moisture content of the wheat in percent.

If you have not yet read "What determines the shelf life of staple foods? ", please read item 1 in particular: The moisture content.

In this case the moisture is even below 10%. Perfect! Let's get started.



The aluminium laminated bag

This is the aluminium laminated bag I will be using. It's a bag with an overall size of 760 mm x 500 mm, which is also available here in our shop.



Buckets or barrels

I'm using a bucket (in this instance with a 30L capacity) to keep the bag upright, making the filling process easier for one, and secondly to be able to use a known capacity as the basis for calculating the required oxygen absorber. After the sealing process the bucket will also serve for storing the sealed bag to ensure the bag will not be damaged by sharp objects and to provide me with the option of stacking.




I now add approx. 20 kg of the wheat into the bag. I am clearly still below the bucket's lip. So I am still using less than 30 l.

When not using a tong-style heat sealer the bag, as in this case, must reach far enough beyond the lip of the bucket to provide sufficient room for folding the bag and applying the heat sealer (see press iron example down below).



O2 Absorbers - prior to opening the vacuum packet

Prior to using the oxygen absorbers I ensure the vacuum packaging it comes in is intact. The packaging features an indicator specifically for this purpose. It's still pink (not bluish-purple). This means no oxygen has entered the packaging and reached the O2 absorber. They are ready for use.



How many oxygen absorbers?

As described in detail under "How to use oxygen absorbers " this is calculated as follows: Take the 30L bucket (and therefore more than the actual amount of wheat) as a basis for your calculation.

Based on a volume of 30L and a full wheat filling the air content is 30L x 0.375 = 11.25L.

This means I would like to absorb (at an oxygen ratio in the air of approx. 21%) 11.25L x 0.21 = 2.36 L of oxygen.

This corresponds to 2360cc, in this case I will use 5 x 500cc O2 absorbers = 2500cc



I place the absorbers into the wheat so that they are no longer visible (here all five packs are still visible). The absorbers could also be added prior to or during the filling process.



O2 absorbers not promptly used

I will not be using the remaining oxygen absorbers at this time. I therefore place them into a preserving jar with rubber seal and pressure cap. Alternately, I could also seal them in a small aluminium laminated bag for later use.



Preparing for sealing

The O2 absorbers are already in the bucket. I quickly squeeze as much air out of the bag as possible and fold it to provide a better surface for the heat sealer.


Sealing with the hand-held heat sealer

This column now illustrates how I proceed when using a hand-held heat sealer.

Sealing using a press iron

This column illustrates how I further proceed using a standard press iron.



The hand-held heat sealer has already been pre-heating for 10 minutes to ensure a quick process. It is already set to setting 2, i.e. only the lower jaw is hot. If your hands are not very strong, you may want to use setting 3 where both jaws will be hot.

I have preheated the press iron to its highest setting to ensure a speedy process. Don't worry, the press iron won't immediately stick to the bag. I'm even using one of the cheapest press irons without non-stick coating.





The first piece has been sealed. I placed the bag between the sealing jaws and firmly pressed the sealer together for 2 seconds. Looking at the seam one can already tell furrowed jaws were used.

To achieve a uniform sealed seam using the press iron and to allow me to apply some pressure with the press iron I place a square tube under the bag (in this case I also have a piece of wood under the tube to allow me to apply the press iron higher up and therefore better, and not touch other parts of the bag with the press iron.). One could also use e.g. the side of a spirit level (unpainted metal only!) or similar items.





Overlapping with the first section of the seal I now seal the second section.

I properly place the bag and ensure there are no uneven areas, i.e. both sides of the bag are pressed together tightly.





On the other end I only leave a small section open to allow...

I now apply the press iron, apply some pressure and move back and forth across the bag. Using this method I continue sealing little by little, ensuring there are no uneven areas. Here too, I first leave the last section on the other end of the bag open to express as much air as possible.





...remaining air to be expressed. The oxygen absorbers now have significantly less oxygen to remove...

This is how the seam looks in this case. As you will notice on the right, it is still missing the last section of the sealed seam...





...after allowing the air to escape from this corner.

...which I am now holding up to the camera.





Finally I seal the last section of the seam beyond the corner of the bag. That's it. Now it's up to the oxygen absorbers to do their job.

I thoroughly again express as much air as possible.



Then I apply the last section of the sealed seam.



Done! Even with the press iron I was able to seal this bag within 2 minutes.



In both cases I thoroughly inspect the sealed seam. If the seam is applied correctly, the two sides can no longer be separated. Instead, the bag can only be forcefully opened above or below the seam. To inspect the seam you can - once the seam is cooled off - try to open the bag from the outside right at the seam

So be careful! If the two sides of the bag can be separated at the seam, the seam is not tightly sealed. Use either more heat, apply more pressure, or extend the sealing time.



A few hours later

The bag's seal is excellent, the seam is tight.

As is evident from this picture, the absorbers have successfully created a partial vacuum after a few hours.

Now it's off to a sturdy container and as cool a storage location as possible!