Home freeze dryer machine

A home freeze dryer is a really good way to prepare for difficult and lean times, allowing you to easily preserve anything you eat. And, the food will taste great and retain nearly all of its nutritional value for up to 25 years when the food is stored and packaged properly.

What is Freeze Drying ?    

Lyophilization or freeze drying is a process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change directly from solid to vapor without passing through a liquid phase. The process consists of three separate, unique, and interdependent processes; freezing, primary drying (sublimation) and secondary drying (desorption).

Freeze drying takes advantage of the scientific principle of “sublimation,” the direct transition of a solid to a gas, by removing ice (the solid) from frozen food as water vapor (a gas). Using sublimation, the food retains much of its original texture, flavor, and nutrition when rehydrated.

Freeze drying is broken down into two simple processes: freezing and vacuum drying. Foods are first frozen to well below 0°F. The colder the freeze the more efficient the next step will be. Once frozen, foods are subjected to vacuum drying. The air and water vapor (gas) are removed from the food processing chamber using a vacuum pump. This includes removing the water vapor that was once inside of the foods. When these two steps are properly completed, the food is dry enough to allow for safe storage at room temperature.

small freeze dryer

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How Freeze-Drying Works?

The fundamental principle in freeze-drying is sublimation, the shift from a solid directly into a gas. Just like evaporation, sublimation occurs when a molecule gains enough energy to break free from the molecules around it. Water will sublime from a solid (ice) to a gas (vapor) when the molecules have enough energy to break free but the conditions aren’t right for a liquid to form.

There are two major factors that determine what phase (solid, liquid or gas) a substance will take: heat and atmospheric pressure. For a substance to take any particular phase, the temperature and pressure must be within a certain range. Without these conditions, that phase of the substance can’t exist.

Water can take a liquid form at sea level (where pressure is equal to 1 atm) if the temperature is in between the sea level freezing point (32 degrees Fahrenheit or 0 degrees Celsius) and the sea level boiling point (212 F or 100 C). But if you increase the temperature above 32 F while keeping the atmospheric pressure below .06 atmospheres (ATM), the water is warm enough to thaw, but there isn’t enough pressure for a liquid to form. It becomes a gas.

This is exactly what a freeze-drying machine does. A typical machine consists of a freeze-drying chamber with several shelves attached to heating units, a freezing coil connected to a refrigerator compressor, and a vacuum pump.

With most machines, you place the material to be preserved onto the shelves when it is still unfrozen. When you seal the chamber and begin the process, the machine runs the compressors to lower the temperature in the chamber. The material is frozen solid, which separates the water from everything around it, on a molecular level, even though the water is still present.

Next, the machine turns on the vacuum pump to force air out of the chamber, lowering the atmospheric pressure below .06 ATM. The heating units apply a small amount of heat to the shelves, causing the ice to change phase. Since the pressure is so low, the ice turns directly into water vapor. The water vapor flows out of the freeze-drying chamber, past the freezing coil. The water vapor condenses onto the freezing coil in solid ice form, in the same way water condenses as frost on a cold day.

This continues for many hours (even days) while the material gradually dries out. The process takes so long because overheating the material can significantly change the composition and structure. Additionally, accelerating the sublimation process could produce more water vapor in a period of time then the pumping system can remove from the chamber. This could rehydrate the material somewhat, degrading its quality.

Once the material is dried sufficiently, it’s sealed in a moisture-free package, often with an oxygen-absorbing material. As long as the package is secure, the material can sit on a shelf for years and years without degrading, until it’s restored to its original form with a bit of water (a very small amount of moisture remains, so the material will eventually spoil). If everything works correctly, the material will go through the entire process almost completely unscathed!

The Benefits of Home Freeze Drying 

It’s been known for many years that the Freeze Drying process is better than canning, freezing, and dehydrating! The freeze drying process causes no damage to the nutrition of the food being preserved. Other food preservation methods like canning and dehydrating use higher temperatures that can destroy more than half of the food’s nutritional value. Also, the freeze drying process retains the aroma, flavor, color, shape and nutritional content, and does not shrink or toughen the food. You can freeze dry single simple ingredients and even every day meals:

  • Use when you don’t feel like cooking.
  • Pack in your box lunches to heat in the microwave at work.
  • Use on your outdoor adventures! Perfect for camping, backpacking, and picnicking.

Being Prepared

A home freeze dryer is a really good way to prepare for difficult and lean times, allowing you to easily preserve anything you eat. And, the food will taste great and retain nearly all of its nutritional value for up to 25 years when the food is stored and packaged properly.

Less Food Waste

If you’re like many of us, we feel guilty when we throw away unused leftover meals, over-ripened fruits and vegetables, and other foods that spoil before we get around to using them. Eliminate the guilt! Freeze dry your leftovers, fruits, vegetables, meats, eggs, and dairy items. Confidently squirrel it away until you are ready to use it! Now, you and your family can avoid food waste and preserve large quantities of high quality food that would normally be tossed out in the garbage.

Special Dietary Needs

The home freeze drying process is ideal for any special diet or nutritional need(s) which can be of concern to folks wanting to store long term foods for emergencies. Common dietary concerns that can be eliminated by home freeze drying your own food include:

  • Organic, non-GMO ingredients
  • Vegetarian and Vegan-friendly
  • Food allergies and ingredient concerns
  • Elimination of preservatives and processed foods
  • Clean, whole, raw foods

Prepackaged, processed meals often include unhealthy additives (i.e., sodium nitrate, high-fructose corn syrup, trans fats, food dyes and colors). When you freeze dry at home, you are assured of the foods that you and your loved ones will be consuming.

home-freeze-dryer

Longest Shelf Life

  • Freeze Dried Foods — up to 25 years
  • Dehydrated Foods — up to 4 years
  • Canned Foods — up to 3 years
  • Frozen Foods — up to 2 years

Food Storage Options

  • Homemade Freeze Dried Foods are cost-efficient and have a long shelf life, not requiring a complicated rotation schedule. This food will be good for up to 25 years, holding its nutritional value the entire time.
  • Canned Foods are the most common method of food preservation. Because of its short 3-year shelf life, it requires a careful rotation schedule to ensure you’re not stuck with expired cans of food.
  • Frozen Foods are usually good for a couple of years if properly stored. The big issue with frozen foods is avoiding freezer burn, and there are also power outage concerns when there is a risk of thaw and ruining the food.
  • Dehydrated Foods typically have a shelf life of about three (3) years when stored and packaged properly. The process of dehydration can destroy around 40% of the foods’ nutritional value. The dehydration process uses heat to remove the water from the food, and usually does not remove all the moisture from the food. This can cause food to spoil and develop mold.
  • Commercially Freeze Dried Foods can be very expensive and may be loaded with additives or contain allergens. Many commercial freeze dried foods have a high carbohydrate count (a must in an emergency situation) but few fruits or vegetables.

What can be freeze dried?

You can freeze dry a wide variety of fruits, vegetables, and meats — Things like apples, peaches, strawberries, bananas, tomatoes, avocados, green beans, peppers, onions, potatoes, spinach, shrimp, chicken, turkey, pork, beef, lobster, and more. Even your favorite meals and desserts can be freeze dried! Lasagna, spaghetti, casseroles, macaroni & cheese, chili, soups and stews, steak, pork chops, pasta sauces, cheesecake, pudding, and pie filling to name a few. You can even freeze dry dairy and egg products too! Ice cream, cheese, yogurt, raw eggs, scrambled eggs, omelets, and so much more! Create healthy, allergen-free and inexpensive snacks or pureed baby foods. Kids of all ages love the taste and texture of freeze-dried foods. And don’t forget about your pets! Homemade pet food and pet treats can be far healthier, tastier, and less expensive than commercially produced pet foods.

What’s the difference between a home freeze dryer and a lab freeze dryer?

While the general lyophilization concept, sublimation, is the same for both, the equipment, and the results, are vastly different. Below are the key differences.

Application

The most apparent difference is in how the two types are used. Home versions are primarily for freeze drying food for preservation, to be eaten later. Lab freeze dryers are used to preserve samples for storage or to change the state of the sample for testing/research. Be careful not to confuse lab freeze dryers with industrial freeze dryers. Industrial lyophilizers are very large, possibly an entire room, and are often used in manufacturing, such as freeze drying pharmaceuticals, or fruit to be put into cereal.

Size and Capacity

Home freeze dryers are overall smaller. They will almost always be an all-inclusive unit with a vacuum pump built in; small enough to fit on a countertop. A lab freeze dryer, however, requires multiple components – the lyophilizer itself, a drying accessory such as manifold and flasks for small samples or a tray dryer for large samples or vials that may need to be stoppered under vacuum or nitrogen. A vacuum pump that reaches an ultimate vacuum of 2 x 10-3 mBar is required, for sublimation to occur. They can be designed to sit on a benchtop or cart, or as consoles that sit on the floor.

Lab freeze dryerLaboratory Freeze Dryer – how much does a freeze dryer costs can range from a similar footprint size as home freeze dryers to significantly larger, depending on the capacity and what drying accessory is used. For example, a manifold is much smaller than a tray dryer. They also use a much larger, stronger vacuum pump with a significantly deeper vacuum.
More important than physical size is its capacity. Lab freeze dryers are offered in a greater range of capacities, both smaller and larger than home units. Home freeze dryers average capacities of 3.8 liters to 15.1 liters (1 to 4 gallons), while lab freeze dryers range anywhere from one liter to 35 liters or more (0.26 to 9.25 gallons).

Temperature

One of the most important factors in determining the right lyophilizer for your needs is the temperature its collector coil can reach. Home freeze dryers get to around -40° C (-40° F) on average. Lab freeze dryers cool anywhere from -50° C (-58° F) to -105° C (-157° F).
Collector temperatures are important in the lab because many samples contain solvents such as acetonitrile and DMSO or acids such as TFA. These solvents require a colder collector temperature to give a temperature differential and prevent melt back of the sample during the lyophilization process. Different materials of construction are also used to handle these solvents and acids.

Measurements

If you’re trying to determine the intended purpose of a freeze dryer, an easy way to tell is the measurements. Home lyophilizers tend to use gallons and Fahrenheit while lab lyophilizers use liters and Celsius.

Cost

Obviously the price tag is going to be a bit different between a home freeze dryer and lab freeze dryer. It may even be the reason a lab tries to make use of a home freeze dryer for scientific purposes. Home freeze dryers on average range from a few hundred to a few thousand dollars while lab freeze dryers tend to start at a few thousand dollars and easily increase to tens of thousands with all of the necessary accessories.

Similarities

Now that we’ve seen all of the differences between home freeze dryers and lab freeze dryers, it’s worth noting the ways they are alike. They are both designed to remove moisture for long-term storage of samples. Both use a vacuum pump, though the home pump is smaller and provides less vacuum than lab freeze dryers require. They also share some similar design traits. Home freeze dryers are designed like a lab’s bulk tray dryer with multiple shelves to place the food (samples) for lyophilizing.

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