Buzzing around Instagram and online freeze drying groups, I see a lot of photos of people showing off their home freeze dried goodies – and a lot of freeze drying mistakes. We got our home freeze dryer earlier this year, and it's pretty easy to use, but there are some things you should avoid to get the best results for your food and your freeze dryer. Some of these tips are for flavor, some shorten your drying time, some avoid messes and a few are real safety issues.
Freeze Drying Mistakes #1 – Mixing Raw Meat with Other Foods
Just like in the rest of the kitchen, you want to avoid cross contamination to prevent the spread of e coli and other bacteria. Scientists use freeze drying to preserve bacteria samples. This means your odds of any bacteria on your raw meat surviving the freeze drying process are pretty high. During the freeze drying process, water vapor moves around the freeze drying chamber. (The sublimation process takes the water in the food from frozen to vapor, skipping the liquid state.) Please don't mix foods like fruits and vegetables that are intended to be eaten raw with raw meat. If you wouldn't mix the foods on a kitchen cutting board, don't mix them in the freeze drying chamber.
Freeze Drying Mistakes #2 – Mixing Foods with Dissimilar Flavors
There are a number of sources that say you can mix and match even strong flavored foods in the vacuum chamber, as long as you put the strong flavored food (like onions) on the top shelves. I'm telling you otherwise. Maybe those folks have wonky taste buds, but when we freeze dried green beans and bananas in the same batch of food, we ended up with green bean flavored bananas. The flavor was subtle, but it was definitely there (and green bean bananas do taste as bad as they sound). Since then, we've been careful to keep sweet and savory foods separate, with good results.
Freeze Drying Mistakes #3 – Attempting to Freeze Dry High Sugar Foods
Some foods like very high sugar content fruit, jams or jellies do not freeze dry well. No matter how long you leave them in, they will still be a little (or a lot) sticky. This is because sugar binds to free water molecules, preventing them from escaping the food. Normally, this trait is helpful for food preservation. Binding up free water slows down bacteria and mold growth, because those microorganisms need water to thrive. Unfortunately, it results in a less than ideal freeze dried product.
How much sugar is too much sugar? The good news is that most plain fruit still works very well, although sweeter fruits like peaches or pineapple will likely require a longer drying cycle. The only fruit I've tried so far that took a very, very long time and still came out tacky was pears. There's a reason I refer to my dehydrated pears as “pear candy“. I'll stick to dehydrating those, since the freeze dried pears came out very similar in texture to the dehydrated pears. Just skip the jams, jellies and other fruit spreads.
Freeze Drying Mistakes #4 – Trying to Dry High Fat Foods
One of the first freeze dryer reviews I read was from a fellow who attempted to freeze dry butter. He ended up with a massive mess. There was butter coating every surface on the interior of his freeze dryer, and it took a very long time and lots of work to clean up.
Of course, this got me wondering how much fat is too much fat, so I tried some pre-cooked, frozen breakfast patties. Never again – at least not unless I heat them up and remove as much fat as absolutely possible before freeze drying. Like the first gentleman, I ended up with fat coating much of my freeze dryer. Even after a good scrubbing, it took weeks for the odor to fade completely. (Thankfully, other foods did not pick up the odor.) The flavor of the finished product was a lot like sausage jerky, and they didn't rehydrate very well (see next mistake). Still, if you were hungry, I'm sure they'd be delicious.
Fat will also go rancid more quickly than other food items, so a meat or dairy product with higher fat levels is probably best used within 5 years. Make sure that if you want to freeze dry meat products that as much fat as possible is removed before drying. Full fat dairy such as whole milk, sour cream and cheese work just fine.
Freeze Drying Mistakes #5 – Freeze Drying Large Pieces of Meat
Perusing the freeze drying forums, I've seen quite a few accounts of people attempting to eat freeze dried pork chops – and having them taste like leather. Bigger hunks of meat simply don't rehydrate well. Even the sausage patties were mighty chewy. For best results, stick to meat that is shredded, ground or diced. If it's normally served in a sauce, soup, or stew of some sort, even better. Rehydrating with plenty of liquid and a lot of surface area for that liquid to soak into makes for a tastier meal. The exception to this rule may be cooked shrimp, which some folks say rehydrates just fine for shrimp cocktails. (I have not tried this yet because we don't eat much shrimp.)
Small pieces of meat also make tempting snacks. (Our strips of fajita beef tasted like meat flavored cheese puff snacks AKA “meatos”.) Just make sure you don't eat too many dried pieces without drinking plenty of liquid so your internal plumbing doesn't get backed up.
Freeze Drying Mistakes #6 – Not Using a Liner in the Pans
The first time I loaded up my freeze dryer, I didn't bother with liners for the pans. After all, they're stainless steel, non-reactive and food grade. Not a good idea. Like a kid with their tongue stuck on a metal flag pole, my freeze dried goodies did not want to come off the pan. If you let them set around until the pans warm up, there's a risk that they will start absorbing moisture from the air and get soggy, ruining your freeze drying efforts. (Winter hasn't been bad, but in summer, when the humidity is sky high, this is a real issue.) Invest in some sort of liners and save yourself a lot of headaches.
I purchased sheets of reusable parchment and cut them to size. You can also use regular parchment paper, too. With care, you should be able to use it for a couple of loads. Wax paper and plastic wrap are a little too flimsy, and I wouldn't recommend aluminum foil because of the long exposure to aluminum for your food.
Freeze Drying Mistakes #7 – Expecting Quick Drying in Hot Weather
Just like your air conditioning, your freeze dryer has to to work harder the hotter it gets. Higher temps add hours to the drying time – sometimes many, many hours. Our unit is in our attached garage, which is insulated but not air conditioned. When the heat and humidity go up (80°+F), I take a break from freeze drying. If you live in an area where it's almost always hot and/or humid, I'd put the freeze dryer in an air conditioned space. Also, don't operate the unit below freezing. You will very likely have water within the compressor (which is normal) but below zero it can freeze and destroy your compressor.
Freeze Drying Mistakes #8 – Freeze Drying Fruit with Tough Skins Whole
For fruits with tough skins like grapes, cranberries, cherry tomatoes and blueberries, extra minutes of prep time will save hours of freeze drying time. Grapes are typically sliced in half lengthwise (like folks with smaller kids probably already prep them). We prep cherry tomatoes the same way. For blueberries and cranberries, I freeze them on a baking sheet before freeze drying, and then give them a very brief spin in a food processor. The goal is to nick the skins ever so slightly so water can escape, while leaving the fruit intact. I've also seen folks poke holes in individual berries, but the pre-freeze method is much faster.
Freeze Drying Mistakes #9 – Filling the Trays with Liquid Before Loading Them in the Unit
It's a simple thing, but may be easy to miss. Liquids spill. So – if you want to load up a tray of something like soup or milk, it's best to limit how far that liquid needs to travel in the tray. Get your try in the freeze dryer, and then pour the liquid in – or load it right next to the freeze dryer and transport it inches instead of feet. Each tray will hold about a quart.
Freeze Drying Mistakes #10 – Filling the Freeze Dryer Too Full
The Harvest Right Freeze Dryer works by pulling water out fo the food and having that water freeze on the inside of the vacuum chamber, forming a layer of ice. Too much food = too much ice = machine that can't finish the drying cycle. I haven't run into this, but others who have say that they needed to empty the unit, place the food in a freezer, defrost the unit, and start the cycle again. Big hassle. Load the unit right the first time and save yourself some trouble. Freeze dry no more than 10 pounds in at one time for the mid-sized unit – 6 pounds is a better limit for high moisture foods. (Check your specific unit for recommended maximum load size.)
Freeze Drying Mistakes #11 – Mixing Food Sizes and Stacking the Food Unevenly on the Trays
This is another problem that I see regularly – people mixing different shapes and sizes of foods, and stacking them unevenly on the trays. Big chunks will still be cold in the middle (and not completely dry) long after the small bits have finished. A photo taken with a thermal imager will clearly show cold blue spots where the food isn't completely dry. Food stacked too deeply has a heck of a time dumping that water from ice to vapor. The top layers slow down or prevent sublimation from the lower layers.
Chop your food thin and/or small for the fastest drying time, and spread it evenly on the trays to prevent cold spots.
These Tips Apply for Dehydrating, Too
Most of these tips apply to dehydrating foods as well. Use common sense in the kitchen, and you'll get good results and safe and tasty food.
Do you have any questions about home freeze drying? Leave a comment and let me know. We've had our unit for a while now, and find it to be a useful addition to our home food storage options. I am an affiliate for Harvest Right Home Freeze Dryers, so if you buy through my site I receive a commission at no extra cost to you. As always, all opinions are my own. As far as I know, Harvest Right is the only company making home freeze dryers, but if you find out otherwise, let me know.
You can read more about our freeze dryer in the post, “Home Freeze Drying – The Good, The Bad and The Ugly“. For tips on on how to optimize your freeze dryer use, check out “Harvest Right Freeze Dryer – Cost Analysis and Optimizing Load Size“.
For more food preservation options, check out:
- New to Food Preserving – Start Here
- How to Can Food at Home – 8 Steps for Safe Canning
- Getting Started with Home Food Drying