Vacuum Sealing

Vacuum packing is a simple concept.  Lower the air pressure (22 inches of vacuum or more) in a container until sufficient oxygen laden air has been removed to slow the development of rancidity and retard the growth of insects.  Within reason, the greater the air removed the better the process will work.  I have not yet found any controlled studies that detail exactly how much improvement in shelf-life vacuum sealing can give for dry storage foods, but it is widely used in the commercial food industry and I have read a wealth of anecdotal evidence from individuals which matches my own experiences that indicates that it does work.

Some developmental stages of insect life may not be killed by this process, but if you can draw more than 22 inches of vacuum it will at the least force the more resistant stages into stasis.  Over time even the hardiest bugs will eventually asphyxiate.  Many people vacuum seal their weevil prone grains and when properly done I have heard no reports of infestations.  Certainly I have had none.

How you draw the vacuum to seal your containers is up to you.  There are a number of electrically or manually operated vacuum pumps on the market, some made for food storage purposes and others that can be adapted to the task.  Of the electric home food storage vacuum pumps the only brand that I have found that receives consistently good reviews are the various Tilia Foodsaver models, of which I presently have their Model 750.

Recently Black & Decker and Sears Kenmore have come onto the market with their own line of home vacuum sealers which bear investigation.  I’m still collecting reports so cannot say if their machines are worthwhile as of yet.  If you have any personal experience with them I’d like to hear from you.

Of the manual pumps, only the “Pump-N-Seal” is actually sold for food storage use.  It looks something like a miniature bike pump.  It requires you to punch a small hole in the lid, cover it with a piece of adhesive tape and place the pump over the taped hole.  You then pump out the container and when you remove the pump the pressure differential sucks the tape down against the hole, effectively sealing it.  I’ve used it and it does work as they claim.  I don’t care for having to punch a hole in the container lid but others have found no problem with this and it’s in common use.  It can also be used to seal plastic bags, but I don’t often hear of it being used for this as it calls for having to paint inside the bag mouth with a small amount of vegetable oil.

It’s also possible to adapt a hand-pumped brake bleeder vacuum pump for food storage use and some have made their own pumps from old automobile air conditioning compressors.

WARNING: To be clear, allow me to point out what vacuum sealing won’t do for you.  Any food that would need to be refrigerated or frozen to prevent spoilage before it was vacuum sealed will still need to be refrigerated or frozen after it was vacuum sealed. Lowering the oxygen content of a storage container can do great things for deterring rancidity, staleness, and insect growth, but if the food has sufficient moisture you’ll only be providing optimum growth conditions for some serious oxygen-hating spoilage bacteria such as the notorious Clostridium botulinum.  No vacuum sealing process suited to home-use can take the place of pressure canning low-acid high-moisture foods.

C.1  VACUUM SEALING CONSIDERATIONS

#1 – Sucking dust or powder into your pump will eventually lead to degraded performance or even damage.  To deter this from happening when sealing dry, powdery foods you can try cutting a piece of coffee filter paper to fit inside of the jar adapter fitting so that any air pulled out of the container must flow through the filter paper before going into the pump lines.  I have also seen used a clear, see-through fuel filter in the vacuum line between the jar adapter and the pump.  This will block all but the finest dust particles and allows you to see when the filter needs changing.  Of course, an opaque fitting will work as well, you’ll just have to wait until air flow is significantly restricted to know when to change the filter.  If the pump flow rate is adjustable, try pumping more slowly to lessen the amount of dust sucked out of the container.

#2 – The harder the vacuum you draw on a flexible container, such as a bag, the harder the bag will press against its contents.  For smooth foods such as beans, corn and wheat this is of no significance.  For sharply pointed foods such as long grain rice, rye and some kinds of dehydrated foods it may pull the bag against the food hard enough to puncture the material.  This is especially the case if the package is will be handled often.  For foods such as this consider putting the food inside of a paper bag first before sealing into the plastic bag.

#3 – Combining vacuum sealing with flushing or purging with inert gasses can improve the efficiency of both.  By drawing out most of the oxygen laden air from a container there is less for the inert gas to have to displace.  This, in turn, means that the final oxygen content in the head gas will be lower than it otherwise would be if the vacuum process hadn’t been used.  Combining vacuum sealing with oxygen absorbers means that a lower capacity (and cheaper) absorber can be used.  It can also extend the absorptive life of the absorber thus allowing it to remove any oxygen that might infuse through the packaging material or through microscopic leaks.

#4 – All of my most sensitive storage foods such as dry milk powders (especially whole milk), dried fruits and vegetables, oils, dry eggs, etc I now seal in pint, quart, or half-gallon glass canning jars using the jar sealer adapter on my Tilia.  This has proven to be an excellent means of preserving oxygen sensitive foods.  The jars and lids are reusable and do not absorb odors.