Freeze drying how does it work

Recipes — Find recipes customized for freeze drying. Freeze drying has four stages: Pretreatment — Food can be prepared before freeze drying it. This is done to change the drying process, or the final dried product.

Pretreatment can be as simple as slicing the food to certain thicknesses. Or by adding citric acids to maintain the appearance of the final dried foods. Some recipes need to be modified for freeze drying.

Ingredient flavors might change from either the drying, or the reconstituting processes. When most people think about freeze drying, Neapolitan astronaut ice cream bars are usually one of the first things that come to mind. But freeze drying is so much more than that. Simply put, freeze drying is the process of removing moisture from a substance without damaging its basic composition.

Moisture not only adds weight but also provides an environment for microorganisms to grow and cause spoilage. Removing moisture greatly increases the shelf life of a substance, as well as reducing its size and weight. Freeze drying may sound similar to the dehydration process, but is actually different both in execution and the final product.

The dehydration process turns liquid water into water vapor with the application of some form of heat. Ovens, food dehydrators, or even sun rays are frequently used to evaporate water into the ambient air. This heat, no matter how subtle, causes chemical reactions to occur within the substance being dehydrated.

These chemical reactions cause a change in appearance, taste, and smell such differences are noticeable when comparing a grape to a raisen.

Freeze drying skips the liquid water phase all together. Substances are frozen and then de-pressurized to induce sublimation. Sublimation is different from evaporation because the water will transition directly from a solid ice state to a gaseous state.

This process prevents the substance from breaking down on a cellular level and helps retain its composition until it can be re-hydrated.

Because some moisture remains, bacteria and enzyme activity is only slowed down, but not halted altogether. This moisture reduction does cause some physical changes in color and appearance. Because of this, freeze dried materials have a much longer shelf life than dehydrated materials. The process also helps preserve its original color, appearance, and molecular composition. The inclusion of an exhaust oil mist filter greatly reduces the escape of oil mist by allowing the exhaust oil mist to re-condense and return into the pump.

Furthermore, oversized oil mist filters are available that really do an amazing job of capturing practically all of the oil mist. Either way no more oil soaked messy sock filters! And with the recirculating oil filter it does not get much better. High quality pumps are quite expensive, but they last a long time with proper periodic maintenance that equates to using a cold trap and periodically changing oil.

Often they can be found on the used market. These upgrades do cost, but they make for a very nice dependable system. A used pump without the oil filtration accessory can be more easily found, with great savings in price, and retrofitted with a new oil filter accessory. Just a thought…. Say David, sounds like you have some experience with vacuum pumps. Can I contact you when I need to replace mine? Where would one find a used refrigerated cold trap?

Ebay is a good place to start. Right now there happens to be a used Welch A listed. As far as used refrigerated cold traps go, or vacuum pumps as well, there are lots of used scientific equipment sellers. If you are near a major big city there may very well be some local sellers.

Its almost a certainty. Otherwise the internet of course. Ebay again is a good start. They have a digital temperature gauge, which is essential to know what the temperature is and see it is working properly while in use. They are very heavy. Two strong people to lift it. Be aware there are volt and volt models. Google the model to find all the technical info. A liter of Cryocool lasts a long time part number SCC1.

There is an old style glass trap insert, and a new style. New style seems more common. Old style simpler but more delicate glass connections to the vacuum line which requires thick walled rubber vacuum hose, Savant quick connects are not necessary but are very convenient. The glass traps are very expensive new. Another source is on Labx. Just looking around that website provides lots of leads for used equipment sellers. Freight costs add to the price.

Finding a local dealer is nice to help in case there is any problem with a unit. A good unit should last a long time-years of service. Avoid those. Incidentally, some units happen to chill to a lower temperature than others-luck of the draw. But it does not have a digital temperature gauge, so impossible to monitor temperature while in use.

One can test the unit by immersing a suitable thermometer in the Cryocool fluid with the glass trap removed. Also, a colder trap works even better for removing water vapor review cryopumping for explanation.

Your choice if you decide to go with Savant. The RVT volt version with the digital thermometer is a better choice I think. Search online for the instruction manual to familiarize yourself with operation and simple maintenance. Older model manuals will refer to old style glass trap use.

Newer manual for use with newer glass trap design. Have fun. David, depending on the oil in the vacuum pump, a cold trap could get cold enough to cause back streaming from the pump. That might actually be an advantage in that it would clean up the oil a bit.

It could easily be cooled to by the refrigerator they already have. That would probably prevent most of the water contamination of the pump oil. The oil demister is really weak.

Even using a larger PVC fitting would potentially be a great improvement. I like these kind of products, I have a water generator, coffee bean roasting whirley popper, would really like to add to my unique kitchen with this unit. Regardless, not sure this would be practical for apartment dwellings. How long does the drying process take. Meat will generally go more quickly than fruit because it has a lower water content. Drying times vary dramatically with temperature and humidity levels in the room the freeze dryer is in, too.

I have my freeze dryer in an insulated attached garage not air conditioned. In warmer weather, I was seeing drying times over 30 hours. Now most loads are around 24 or less. I have been thinking about a freeze dryer for awhile now.

I consider myself to be somewhat of a prepper. I pick up a few cans here and there but not nearly as much as I think I may need if disaster were to strike. I also hate the produce aisle in the winter months. I also prefer to buy organic produce. Like others, the cost has been a deterrent for me. I do have a couple questions. Are butter and milk to fat laden to freeze dry into powder? Also you mentioned mylar, I have a foodsaver would that work the same for preservation if I put and oxygen absorber in it?

Does the machine come with drying times for different foods and a list of foods that can be dried? Or is there a book somewhere with directions? Sorry for all the questions but I am really interested in this.

Milk and other milk products like cheese, sour cream and yogurt work just fine. My boys inhaled the yogurt drops that I made. Foodsaver bags, while useful for a great many things and the preferred option for freezer storage, are not recommended for long term storage over 2 years. Freeze dried food can also become brittle and powdery, which could gum up your vacuum sealer. Great information. I went on a weight program and lost about 60 pounds, but it was costly.

Part of the product was freeze dried meals. I then found replacement products, bars and shakes and through a food storage site, I purchased freeze dried meals in the 10 cans. I have about ten cans, and they cost about When we move to another house, I will for sure be getting one of these, I will be living closer to my step daughter and step daughter in law. It will be nice to share with them.

Hi Laurie I am a flower lover and would like to know if there is a chance to process some flowers like roses same as food stuff with this system? Rgds Abby. Yes, the home freeze drying unit can be used to freeze dry flowers.

I bought one of these freeze dryers a month ago and have run 21 loads thru it with not much difficulty. I, like you, drain all the hot oil from the pump right after the freeze drying cycle completes. I then add exactly 23 oz of vacuum oil to the pump and never have an overfill misting problem as you describe. So far I have freeze dried chicken, turkey, ham, apples, bananas, potatoes and a couple of different entrees.

I tried to freeze dry hot dogs that I had previously boiled and made a giant mess out of the inside of the chamber. To make matters worse, the hot dogs refused to completely dry. I have successfully freeze dried brown hamburger but you need to be diligent in removing the fats and oils and put into the drier ground beef that is dry or you get grease on the interior of the freezing chamber as well. I have been keeping track of weights into and out of the drier so I know what percentage of water each food is.

I have also been slowly increasing the size of the loads I put into the drier and I am currently up to about 4. This machine is great and I have also found the customer service very helpful. Thanks for your feedback, Dennis. I applaud you on your dedicated record keeping. For one that lives in Southern Arizona, it is not unusual for the internal temperature of our home to be 80 to 82 degrees for 3 to 4 months of the year during the summer.

How does temperature impact the life and quality of the freeze dried food? The worst option is extreme temperature swings, which may cut storage life in half possibly even worse. Anything that you could do to reduce the temp and keep it steady would help. My husband suggested under bed storage, since it would be likely to stay cooler there, or a root cellar type setup where you could use earth temp to keep your storage cooler.

How would I be able to freeze dry liquids such as flavouring extracts banana extract, strawberry extract etc , sometimes they contain oil as well so could anyone shed some light on how I could turn these liquids in to powder forms. You could freeze dry the fruits themselves, powder them, and use them for flavoring.

Freeze dried fruit powder is very delicious, and adds color as well as flavor. You might have covered this so sorry if you did. We were recently given the harvest right dryer and I was wondering where you read up on oil filtering. There are discussion threads in various online groups. I use a Harvey Filter. We prefer the flush kit for filtering oil. Its the only product out there that is mess free, and pretty simple to use and install.

They also warranty your pump for a year. Which is nice. Does that kit void the original pump warranty? Not that that would be an issue if they take on the pump warranty. That canister filter is a good idea, but how many batches can be dried in the Harvest Right before the filter canister fills with water? Water is the main contaminant as far as volume is concerned. It needs a water separator with visual indication so you can see when it needs to be changed or emptied.

Do you think that you could hook it up to solar panels? If so I wonder how many you would have to get and how many batteries? If you could find out for me, I would be grateful.

Thanks, cat. I am double checking with Harvest Right to see what they recommend. Sunlight intensity and availability varies greatly. We have found that freezing our food before putting it into the Harvest Right really helps cut down on the cycle time. Also, using parchment paper under the food is very helpful. My wife and I have had one of these machines for about a month. We love this machine, the kids love the food.

My favorite part is to take dinner leftovers at the end of the week and dry them, then we reconstitute them to see if we like it. Everything tastes just the same as it did the first time! I would definitely recommend it to anyone. I am becoming intrigued with this whole freeze drying concept. What concerns me is the oil refill. How often do you replace the oil in a typical month? How much does it cost to replace the oil?

Also, after reading that the freeze dryer pulls in about watts an hour got me wondering about the added cost of running the dryer. In my area, the electricity costs 8. Since it takes a typical 24 hours no? Of course, having food around that can last 10, 15 or 20 years is a comforting feeling and you really cannot put a price on that when things do turn south.

One of the first things I did was buy an oil filter, which allows me to reuse the oil safely. We drain after each batch and freeze it, then filter. I did buy a Harvey filter, but many people just use simple toilet paper filters and those also seem to work well. Yes, the electric costs could add up if you were to run non-stop. Which reminds me, I should dig out the Kill-a-watt meter and hook it up to see how much I draw for a full load. Now, if you wanted to have a set up like a lady I know in Florida who has a dedicated room with four freeze dryers and at least two of them running at all times, that would be a jump in the electric bill.

Plus, food prices just keep creeping up. Oh, one other thing. Salmon and golden chanterelle mushrooms? The salmon I am guessing would not be ideal to freeze dry due to the fish oil? And any experience freeze drying Chantrelle mushrooms or any mushrooms for that matter?

Most seem to freeze dry fish raw. The storage life would be shorter years? People also freeze dry mushrooms. They turn the oil black from the spores , but it works. They can be freeze dried cooked or raw. I am learning sooo much from reading the questions and your comments. Thank you all who share. She has learned how to hike for days, taking no packaged foods or water, just living off the land. The 13 plants she features are found everywhere humans are on all continents around the world coming quickly to Antarctica as the ice melts.

Hi Marsha! Her palate is wilder than mine, though. Some of her plant suggestions I enjoy, but with others the bitterness is too much for me yet. It sounds like you, too, have been doing your research on the quality of the food supply, and are looking for better options than the current status quo. Sometimes it all just makes me shake my head — how can we have such an abundance of cheap calories, and still be suffering from malnutrition?

But then you look at the dead soil, how far the food travels to the table, the high level of processing, all the additives and preservatives… we can do better. Hi Laurie, I just took the leap tonight and purchased a red regular sized Harvest Right freeze dryer. It was not an easy purchase and now my husband is angry with me. Nothing new, he fought me for 2 years on getting rid of cable t.

Yet, the initial output for the new T. I really appreciate your site and all the honestly answered questions, this will be a big help in the future when I receive my unit. Her last trip she lived on granola bars which to me is just gross, with all the garbage they put in them.

Hi Nanc, and congratulations on your freeze dryer purchase. Freeze dried fruit is amazing, and freeze dried just about everything else tastes like FOOD instead of preservatives and fillers. Freeze dried cheese is intensely cheesy. If you cut it in thin slices and freeze dry, they taste like cheese crackers — except no cracker!

I watch for sales and buy in bulk so I have enough to freeze dry. Pickled beets and sweet potato fries make excellent snack food. So many tasty things to try…. Being from Alaska I expect that fish might be one of the main ways we will want to use the unit… for both fresh fish and smoked fish. I was wondering about the foodsaver that we already have.

The trouble with free drying smaller fruits and this goes for dehydrating, too , is that the fruit skins are designed to keep the fruit from drying out. Theoretically you could dry them without pretreatment, but it would take much longer and they might still be prone to damp centers. 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. The person making them mentioned that the biggest concern which is important cooking any fish, of course is not to overcook, or it will get rubbery. It does tend to be a little drier, too.

Whichever way you plan to store, oxygen will turn the fat rancid, so either vacuum sealing or O2 absorbers would be a good choice. It vacuums out the air and then seals the plastic.

Am I missing something? Foodsavers need texture on the bags so that the air can be vacuumed out through those little dimples. Mylar presses flat, preventing air from being sucked out. People have also used attachments and straws and all sorts of other bizarre approaches, but the strip is the easiest. That said, if your O2 absorbers are working properly, sucking air out is redundant.

Have you ever used your FoodSaver to seal a chip bag? Same concept. Great review, thanks! Now if someone asked you to freeze dry a load of food, what would you charge? The food tastes very good, and I have teen boys in the house. I guess I asked wrong, sorry. I meant what if someone came to you with things from their garden, all cleaned, cut and blanched and wanted to freeze dry them in your machine.

How would you go about calculating it? It depends on how technical you want to get. Here are estimated electrical costs from the Harvest Right website:.

At peak, the freeze dryer draws about 16 amps, but on the average about 9 to 11 amps watts of power per hour. A dedicated 20 amp circuit is recommended. At peak, the large freeze dryer draws about 9 amps, but on the average about 5 to 7 amps watts of power per hour. Figure in your electrical costs, the unit cost per load, something for your time, some money for oil and filters, and then you probably want to add some padding to the cost if you actually want to make money doing it.

I really appreciate your observations. I too am having a hard time with the cost, but, we just switched some of our canning fish to a Can Canner. Those are really expensive but are great in transport and shelf life. I like it! Thank you again! We still use a mix of food preservation options, but the freeze dryer has become an option that we are using year round instead of just harvest season.

For instance, right now our neighbors have many extra eggs spring production is going crazy. I like to support their farm, but we can only eat so many eggs at one time. Now we have a stash for when production drops, for emergencies, or quick meals. They taste like eggs, not foam rubber. Confession — I think my husband used a little too much butter with the last batch he prepped, as the freeze dried egg bits tasted a little like buttered popcorn.

I marked those to eat sooner instead of later because of the higher fat content. The freeze dryer also gets the boys to eat more veggies. Freeze dried sweet potato fries and sliced pickled beets disappear when I leave them in the pantry near the chips and crackers. The fat makes a mess in the freeze dryer and has a tendency to go rancid over time. Gotta try the eggs mundel.

It sounds good! The Mylar bags can be reused of course,capacity will be reduced. O2 absorbers are one time only — no way to refresh those at home. I have a ton of greek yogurt…I see your boys love yogurt drops which I will do…. It will shed a lot of crumbs, but you could do it.

Just make sure to line the tray so the yogurt comes out more easily. You could add a slice of fruit on each yogurt drop, fresh or dried. I would make sure to allow plenty of drying time, because drops without added fruit will be done more quickly than those with fruit. The Platinum pump has a gas ballast valve that should reduce the contamination of the oil. It costs a bit more, but if it works well it would be worth it. I do know that Harvest Right is now recommending that users drain the oil with each use and filter it.

I would love to hear some owners comments on durability, what issues have been had and replacement parts cost. Another question I have is in regards to the vacuum pump, could I use an oil free Teflon ring pump instead? I have a couple constant duty ones that generally run 10k hours before new rings are needed, and they are cheap and takes 30 minutes to do the job. I would need to know the specs of the Harvest Right one to compare and or adjust the suction required.

We use an old Brita filter with a toilet paper and coffee filter combination filter. Works well. How can I get off of the notify me of new comments line? I love this site but phone goes off too much. Would rather just check site every so often as it is a very informative site. Thank you very much. That should stop notifications. Thanks for asking instead of doing something like marking it as spam.

Oh, and disregard earlier message. No way I can unsubscribe to this site. Bad mom! They still have young, nimble fingers. Saturdays are typically homestead updates, musings and seasonal links.

Thanks for the tips! Ah — following now, and your emailed photo came through. Our pump is on the same counter with our freeze dryer, sitting just behind it, so the vacuum hose forms a gentle s-curve — no pinch.

We also rearranged the drain hose underneath so it exits out the right side of the unit instead of left. The left side of the unit faces the wall, and everything we need to access is now on the right side.

Another question for you. I was talking to someone and she said it was very loud. What is your experience? It is fairly loud — think vacuum cleaner. Thank you for the thorough review! I recently started thinking about freeze drying at home because of my food issues — celiac and for our cats dietary needs.

After researching grain free raw food diets for cats, I started thinking about dry food, bc the cats like to eat the crunchy stuff every so often too. So I thought freeze drying would do the trick since they love the freeze-dried Halo wild salmon. I looked up commercially produced freeze-dried raw foods and sure enough I was disappointed with everything I found in the ingredient lists.

I scrolled through some comments and wow was that Jay guy argumentative, I ran out of steam after that , but I have to agree with the reasons listed for not eating from metal cans, like toxins and other unsavory things packaged up with the food.

Not to mention the flavor and mushy texture of canned food, and the fact that most cans inherently are lined with the estrogen disruptor- BPA. Glass jars are fine if you have the storage space and the jars, although I do think that O2 absorbers are a must for longer storage of any meat products.

I would like to know if you have done any research with desserts. I bake certain things every year and sometimes multiple times in a year. I would use a food dehydrator mainly for that, however your posts indicate that sugars do not do well. Just curious as I am a manic baker and using a dehydrator for this purpose would surely lighten my load. Thanks in advance. Which system, in your expertise, would work better for fruits such as lemons, limes, lychee, pineapple, mango…in other words, tropical fruit…freeze-drying or dehydration?

Sure, vacuum sealing with oxygen absorbers will extend the shelf life for dehydrated foods, too. Not as much as freeze dried, but it will help. Thank you for the above and the courage to answer a variety of questions. I began this morning with discussing food storage with my sister — for an emergency and even a potential financial crisis that I am convinced will happen.

Yes, I thought Y2K would take place. It would have caused issues but entities prepared early enough. Now, that is what I would like to do. I know units can cost a lot of money.

I considered what my interests are and that is food value nutrition and also taste. Ever eaten C or K rations for any length of time? I have and even MREs get somewhat boring. As you point out, canned foods are less expensive but shelf like is a definite consideration as well as nutrition. It has been pointed out that you need a source of good water to rehydrate. So, plan for that also. Again, thank you for a well prepared article and planting the idea that I need to seriously consider purchasing a freeze drier for my food storage.

Hi Neil. Glad you found the discussion useful. I consider the time, effort and money we put into our food storage to be a worthwhile investment, just like the different options we now have for providing fresh water. Before we invested in the freeze dryer, we invested in several different water filtration and purification options, and several water storage options.

So far our well water is safe to drink, but many in our area have had their wells contaminated by factory farms. I love the thing. Run it every day. Start at bout 10 pm so freezing last till 7am and noisy drying part usually ends before bedtime next eve. Funny nobody would consider driving with no spare, but no spare food or water, no problem.

Go figure. PS: your site is great Laurie. Thanks for sharing your experience and note on timing, and thank you you for your kind words. Heck, whole meals are just a mouse click away in many areas. Living out in the country and being snowed in on occasion, as well as job loss, have helped me to appreciate a well stocked pantry. Amen to that William Parker and Laurie Neverman. In massive ice storms in our neighborhood here in the Ozarks knocked out power for up to a month, now just about everybody in this region keeps at least several weeks of food on hand.

The blackberries are going crazy! Zucchini and peppers and beets are already ready to harvest! ChrisF, you are a couple months ahead of us. We had been looking at the Harvest Right Freeze Dryers for some time due to the initial cost, but our organic garden was just crazy this year.

So we purchased the large stainless unit in August and the power switch has not been turned off yet. If you want the very best nutrition, taste, extended shelf life for family, kids and grandkids…the choice was very clear. Our unit will pay for itself in a year or 2 if you look at the cost of commercially freeze dried food….

Our freeze dryer is awesome…if you are concerned about the best quality food for any real world scenarios — and there are a ton of them, a Harvest Right Freeze Dryer is the clear choice…its all about family priorities. Something I have not seen discussed is the nutritional value of the freeze dried foods. Also, I juice my veggies with an omega very juicer. Can you freeze dry juiced veggies and if so, what nutrition do u lose?

Your dry time would be fairly long to remove all that liquid. Research has shown that while freeze-dried fruits and vegetables contain slightly lower amounts of certain vitamins, they are rich in antioxidants and fiber. Most researchers agree that the amount of nutrients lost from freeze-drying is miniscule.

That said, the freeze drying process does not cook the food, so it would still be raw and the majority of vitamins should be intact. I want to Freeze dry a homemade baby formula. I make the baby formula daily. Each batch is about 65 oz. After reading your article I wondered if this would be a good product for me. Any advice or direction you could give is most welcome. I have read the majority of the comments including those from last year.

There are some major and minor points that I have not seen discussed but again I may have missed some. I may be brief on some points, however this might get long so grab something to drink first.

The gentleman that thinks that we should all shop at Walmart forgot a few things to factor into his cost analysis. The cost to go shop for said items is one. Fuel, bus or taxi fare all cost money. Even ordering items online cost shipping.