Hi all,

When I do batches of food in my freeze dryer, I usually seal them in 7.5 mil mylar bags. I put in an oxygen absorber, then throw it in the chamber vacuum sealer.

Do you suppose this is a "belt and suspenders" overkill? The gauge on my vacuum sealer indicates 0.01 MPa when I seal.



And the bags come out looking like this:




Not sure how much to trust the gauge anyway, as it's obviously a Chinese machine (note the "Off-No" switch).

Not overkill.  Cheap insurance.

Not overkill but does come with some downsides. Vac sealing delicate items like most freeze dried foods can crush them. The result can vary anywhere from mildly cracked and broken up chicken to crushed & powdered squash. Use the vacuum sealer only on foods that aren't subject to being crushed or foods you don't mind being crushed and it will be an added layer of redundancy.

I will also note for sharp foods vac sealing increases the risk of a bag puncture.

For really delicate foods purge with nitrogen before tossing in the O2A and sealing the bag (no vacuum).

It's overkill because a properly sealed bag with the right size OA is virtually fail proof. By vacuum sealing you introduce the possibility of puncturing (and it being so small you don't notice) which is a risk that would otherwise not be there had you just used an OA

Below is info on OA sizes per bag size and food type. I also only buy mylar from them or TopMylar.com


https://packfreshusa.com/learn/#what-size

How does this machine work?

My fear is that I will have a non-vacuumed Mylar bag, it will have a puncture, and I won't have any way of knowing. With vacuum-sealed Mylar bags, I can tell at a glance is the seal wasn't good or if they were punctured.

All of our Freeze Dried fragiles go in a ball jar and then I pull a vacuum on the jar.  Super easy to get into and then reseal.

@MrEG

Not sure if I should talk about how the machine performs, or the process by which it performs it’s function, so I’ll briefly address both.

The process: Instead of sucking air out of the bag, then sealing it like a FoodSaver-type vacuum sealer, a chamber sealer has (as the name implies ) a chamber in which you put a bag. The air is evacuated from the chamber, and since the pressure is the same inside and outside the unsealed bag, the bag doesn’t collapse. When the chamber is fully evacuated, the sealer activates, sealing the bag, then air is let back into the chamber. Since there is a vacuum in the now-sealed bag, the atmospheric pressure compresses the bag. Among the advantages of the chamber sealers is that it’s pretty easy and non-messy to seal dusty foods or even liquids.

How this cheap Chinese model works: Pretty well. I knew from a few YouTube videos that I might be in for some repair work if I went the Chinese route. One video showed a guy having to repair wiring. Mine had been dropped, had a dent, and the vacuum pump had broken it‘s mounting screws. A trip to the hardware store, and I was in business. I figured it was worth it for a machine that worked and was less than half the price of the smallest Avid Armor unit. It provides a great seal and a really full vacuum in the bags.


As to puncturing the bags, I recognize that possibility though in the hundreds (thousand+?) I have done this way, the only failures have been incomplete seals, never punctures. My usual practice is to set the bags on the counter for a couple days before putting them in the storage area. If there’s a failure in the bag/seal I should be able to spot it.

Thanks to everyone for their input so far.

Excellent synopisis!  

Thanks for the description.