So I made my own contraption which seems to work fine and the first result is promising – now I’ll wait a week or so, monitoring the vacuumed jar and see if everything meets the expectations.
It consists of an ordinary 1.5 l supermarket food container with a rubber seal and a small customary brake bleeding pump. I veeery carefully drilled a 6 mm hole into the lid of the container to receive a tight-sitting fitting that was additionally sealed with some good old JB Weld. I plan on re-using food glasses from the store.
How it works:
This method works only for thoroughly dry and sprinklabe ingredients like e.g. grains, beans or flour. It protects the product by removing the oxygen in the container and thus keeping it from deteriorating. It does not preserve anything by killing harmful bacteria etc. as other preservation methods like canning or pasteurizing do.
Fill a storage jar with the dry food you want to preserve and ideally add a fresh desiccant bag on top. Make sure to (re-)use a jar that comes with rubber-sealed lid, otherwise the whole thing will not work. Close the lid just hand-tight as you would normally, then put the jar into the vacuum container, connect the tube to the fitting and start pumping. My bleeding pump couldn’t muscle up much more than -520 mm hg (that equals around -0,7 bar) of vacuum, but that was sufficient to seal the jar tight enough. When done, remove the hose (*hissss*) and retrieve your sealed jar.
To assert that everything worked correctly, take a closer look a the lid of your food jar:
After extracting the air you can see it’s buldged in in the middle just like on a store-bought sealed jar. The rubber seal in the lid is now pushed onto the jar’s rim just by the surrounding air pressure, sealing it shut and it does the characteristic plopping sound when opening it. If not, something went wrong.
Edit: Five days under constant monitoring now and the vessel remains unaltered, the lid is still bulged in. I think I trust it now.