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:
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
The aluminium laminated bag
Buckets or barrels
O2 Absorbers - prior to opening the vacuum packet
How many oxygen absorbers?
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
Preparing for sealing
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