A question was asked in the comments yesterday about pre-freezing foods for the freeze dryer. There are several reasons I do it and probably additional reasons that others do it.
The freeze dryer freezes food at a much lower temp than our home freezers. According to Harvest Right, foods are frozen at -20 to -50 degrees F. Home freezers freeze things to about zero degrees. This has nothing to do with why I pre-freeze some things . . just a bit of info I thought you might find interesting.
The area in which the food trays are placed is basically a cylindrical shaped “box” with the trays. As the freeze dryer is “drying”, the water is pulled out of the food and it accumulates on the inside of the cylinder. The ice can get very thick on those walls, depending on how much liquid is being pulled out. The freeze dryer has an optional “defrost” cycle, which heats up the cylinder and melts the ice. That takes a good bit of electricity so I usually let it defrost on its own. The water drains down the sides of the “barrel” and runs out through a tube that is built into the freeze dryer, and accumulates in a vessel of some kind that I have on the floor where the tube can drain into it. I’ll often get a gallon or more of water out of the freeze dryer, depending on what type food I’m freeze drying. If I were freeze drying fresh tomatoes, I’ll get more water than if I’m freeze drying okra.
The “barrel” sits at an angle so the water drains towards the back and out the tube.
You can see pictures on the Harvest Right website.
There are basically three scenarios where I pre-freeze.
First, if I’m freeze drying something liquid, because the freeze dryer sits lower in the back, anything I pour into those trays, if I fill them then stick the tray into the freeze dryer while the contents of the tray are in liquid form, some of it is going to drain out the back of the tray and make a huge mess. Ask me how I know this! Eggs! That was a mess to clean up. Thankfully, I put the first tray in, saw what was happening and didn’t put the rest of them in.
So, when I’m freeze drying anything liquid, I will pre-freeze the food on the trays and I’ll also pre-freeze (kinda like pre-heating the oven), the freeze dryer.
Second, if I’m freeze drying shapes. Sometimes I make yogurt bites where I mix homemade yogurt with mashed fruit and a bit of sugar (strawberries, blueberries, bananas, etc.) and spoon those into the little silicone ice trays that have shapes. I’ll mix the sugar and fruit into the yogurt, spoon it into the silicone trays and freeze it. Once it’s frozen, I’ll dump them onto the freeze dryer trays, keep them in the freezer til the freeze dryer is pre-frozen. Otherwise, they would melt and lose their cute little shapes. We all know about losing those cute little shapes, right! 🙂 I’ve also poured chocolate milk into the silicone trays and made chocolate milk bites.
Third, if I pick a bunch of tomatoes and okra, it may not stay fresh til it gets a turn in the freeze dryer so I’ll cut it all up, put it on trays and put it in the freezer and basically store it in there til the freeze dryer is available. With okra, onions, peppers – things like that, I can freeze it on the trays, then, because it’s kinda dry, I can put it in zipper bags and keep it in the freezer til I’m ready to freeze dry it. Tomates are kinda liquidy and when they’re frozen, they’re in a sheet so I try to take them directly from pre-freezing to the freeze dryer.
The first two things I mentioned . . I HAVE to freeze dry those first. The third does not have to be pre-frozen. If the freeze dryer is empty and I go out and pick tomatoes and okra, I’ll come right in, cut it all up and get the freeze dryer going.
You may remember earlier this year when Vince bought a ton (almost) of bananas. It took about six freeze dryer loads to get all those bananas freeze dried. From start to finish – freeze dryer defrosted, oil changed after every load, it takes at least 3 days, depending on the moisture level of the food and how easy it is to remove the moisture. Those bananas would not have lasted 15 days so I froze them all on trays and as one load would finish and the machine defrosted, I’d stick four more trays in.
Hopefully this makes sense. I know sometimes when it’s something you’ve never seen done, my posts leave more questions than answers so, as always, thanks for the questions.