A freeze dryer is a machine that turns food into lightweight, shelf-stable snacks. It works by freezing your food really cold, almost like ice, and then it slowly warms it up. But here's the trick: as it warms, it doesn't turn into water again. Instead, it goes from a solid (frozen) directly to a gas (vapor) without becoming a messy liquid in between. This process removes all the water from the food, which is what causes most spoilage.
Here's a more scientific explanation of how it works:
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Freezing: The first step involves freezing the food or substance to a very low temperature. In the case of food, this is usually done well below the freezing point of water (around -40 to -58 degrees Fahrenheit). This freezing step solidifies the water within the food.
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Vacuum Chamber: The vacuum chamber lowers the air pressure, making it easier for the ice within the food to transition directly to vapor.
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Sublimation: During the sublimation process, the frozen water in the food turns into ice vapor (water in a gas state) without melting into a liquid. This is achieved by maintaining a low pressure in the chamber and gradually raising the temperature. The ice sublimates, meaning it goes from a solid (ice) to a gas (vapor) without passing through the liquid phase.
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Removing Moisture: As the ice sublimates, it is drawn out of the food and collected in another part of the freeze dryer, usually as a solid in a separate container. This leaves the food completely dry and free of moisture.
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Sealing: Once the sublimation process is complete, the freeze-dried food is usually sealed in airtight packaging to prevent moisture reabsorption and to maintain its long shelf life.
We invested in our own freeze dryer this year and here are a few lessons that we learned:
- There is a learning curve.
This isn't a difficult machine but it does require some time and effort to learn how to use it. Do not expect to plug it in and magically have success with every run.
- The machine is loud.
It is not a regular kitchen appliance. It isn't something that you would set on your counter, like a toaster, and just let it run. The noise will interrupt normal conversations.
- The machine produces heat.
During the process, the freeze dryer machine will produce heat. The process of freezing the food, heating it and maintaining the pressure will increase the temperature in a room. This could be strategically used locating it in an area of the house that is normally colder during the winter months. However, you may need to consider the cooling needs around the machine during the summer months if you plan on using it year-round.
- The temperature affects the duration cycle.
We obtained our machine in late April and continued to use it during the heat of the summer months. We noticed that when the temperature and humidity are higher, the length of time required to process anything takes much longer. You cannot rush this process by turning up a knob, like on your stove. You simply will have to wait longer for the product to be complete.
- Each machine is different.
We have spent time on the various social media platforms researching tips and tricks from other users of this machine. I don't believe that the individuals are lying when they state that it only takes x number of hours to process strawberries. However, it took me much longer. Even with the optimal temperature and humidity, I didn't always gain the same results from using a "recipe" from another user. It requires a learning curve to understand the your machine and it's specific characteristics.
- It takes a longer time to process than you would imagine.
This is not an air-fryer. It is not a set and wait for it type of machine. Most candy takes several hours to process and any fruit or vegetables with any type of moisture content will take over 24 hours. For example, the freeze dried pineapple is a great treat but it took us almost 48 hours to process. The good news is that you can adjust the settings to add additional dry time so that you do not have to be there the second that the machine detects that the product is complete. While the machine will work for that period of time, you are simply checking on it periodically.
- It is a great option for preservation in your toolbox.
When our garden was cranking out the produce, I could set up the dehydrator, the freeze dryer and also be canning and/or freezing at the same time. Adding the freeze dryer is a great addition to help store our harvest for later use during the winter. As anyone that has felt the time crunch of processing all of the fresh produce before it spoils, having a machine like a freeze dryer that you can set up and let it run is very useful.
- You may experience a smell and taste crossover with different batches.
I have only experienced the crossover of taste when running a batch of cheese after multiple batches of candy. By changing the oil and cleaning the machine more carefully, this didn't happen again.
I haven't run anything with a pungent odor like garlic or onions. I have heard that running a bread run after those type of products will help to absorb any lingering taste and odor. It may be worth a try if you were to experience this issue.
- There are many ways to store your finished product.
For short-term (within the next six months) use, we utilize canning jars with a vacuum seal. We also use mylar bags. They are good way to store our products that do not take as much space as jars. I would like to find the bags that will stand up, as our current mylar bags just lie on the shelf and can fall to the floor when you move things around in your pantry.
The use of desiccants and oxygen absorbers are needed to maintain freshness over a long period of time, but we do not have the experience to provide insight on this portion of storage.
- We have tried multiple items.
I loved using the freeze dryer for berries. My daughter was still young enough to get choked by giving her regular blackberries, raspberries or strawberries without taking the time to cut them up. When the berries are freeze dried, they will crumble. I no longer have to worry as much about the choking hazard and she can enjoy this treat.
We love freeze dried green beans for a healthy snack. They are easy to pack for soccer games and much healthier than traditional chips.
The zucchini didn't work well for us. I think I didn't run it long enough. It was also bland. I think that if I seasoned it before processing, then it may turn out to be a fun and tasty chip-alternative.
Our garden produced an abundance of peppers this year. We have eaten them fresh, made and canned cowboy candy, dehydrated them and freeze-dried them. We haven't had the need to break open a bag of the peppers yet, but we are excited to have this as an option for the winter.
- Our biggest surprise was tomatoes.
We discovered that slicing the tomatoes and freeze-drying them produced a tomato that would crumble easily. We ran them through a coffee bean grinder to turn it into powder. We then added water to the tomato powder to produce tomato juice. To me, the process of slicing tomatoes and placing them in the machine is much easier than canning fresh tomato juice. The tomato powder takes up much less space on the shelves than the larger jars. I wish I would have tried this one sooner. I can't wait to harvest and freeze dry more tomatoes next year!
- We still have many things that we want to try.
Things like eggs, leftover soups, corn and other vegetables are on my list to freeze dry next. I also want to try the cheese pieces again. I have tasted cheese freeze dried by another vendor and they have a texture similar to cheese crackers but without all of the added preservatives and harmful ingredients.
- People love freeze-dried candy.
Since we were already set up at the farmer's market, we decided to sell the candy to help pay for the investment of this machine. I had no idea that they would be this popular. To be completely honest, we have spent more time making (and eating) the candy than I would prefer. We will continue to produce a small amount to sell to our customers, but we hope to diversify our usage of this machine.
Overall, I am very satisfied with the investment. I believe it will help to provide and store good, healthy food for our family. We are looking forward to using this machine much more in the future.
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