You must be buzzing with a lot of questions in your head about drying foods and their benefits. Are you trying to freeze dry foods to preserve your food for a longer shelf life? Do you know how to freeze dry food at home?
Here is what you should know about freeze-drying food.
1. What Is Freeze Drying?
Lyophilization, commonly called freeze drying, is the process of dehydrating food based on the sublimation of water in the food or product. Freeze drying removes the water content present in the food by vaporizing it.
Freeze-drying food is superior to all the other preservation methods, like canning or freezing, used to preserve food as it changes only the texture of the food. This is because, despite all the moisture vaporizing, freeze-dried food’s nutritional value and taste remain the same.
Freeze-dried foods are lightweight and thus are easier to carry anywhere in your emergency preparedness kit with all their nutrition intact. Freeze-drying food at low temperatures gives food a long shelf life as it kills bacteria and can be a great option for camping meals.
2. How Does the Freeze Drying Process Work?
There is more than 80%-90% water in any raw food; free water molecules get frozen, and bound water does not. All the free water and moisture in the food when freeze-drying must be removed, and frozen water should remain frozen.
The freeze-drying process involves three steps which are:
- Freezing under normal atmospheric pressure.
- Frozen-free water is removed with the sublimation technique known as freeze drying.
- Drying foods under preferred humidity by removing remaining water.
The freeze-drying process is to be done under specific controlled conditions where the frozen water should not melt but evaporate. This ensures that shape, nutrition, and taste are not affected.
3. How to Prepare for Freeze-drying?
Knowing what types of products can be used to freeze-dry is very important. Not every food can be used for freeze-drying. High-water content products that can sustain their shape and nutrition are used for freeze-drying.
3.1. What Food Can Be Freeze dried?
Food with high moisture, such as your kitchen garden, should be used for freeze-drying. Here is the list of such foods:
- Fruits such as apples, bananas, pears, strawberries, blackberries, and oranges are best suited for freeze-drying. The freeze-dried version of all these fruits will taste as good as the original fresh version.
- Most raw vegetables, such as carrots, potatoes, tomatoes, and pumpkins, are high in water and can be freeze-dried.
- Non-vegetarian food products, such as meat, eggs, fish, etc., can be freeze-dried as they are high in moisture.
- Food grains and cereals such as rice, wheat, grams, and beans can be freeze-dried.
- You can also try freeze-drying other foods high in moisture, such as beverages and spices.
3.2. Food That Should Not be Freeze-Dried
Now that you have learned what food items you can put under the freeze-drying process, you must know what food should not be used for freeze-drying. Mostly food that can not be recooked or consumed as it is should be avoided because eating raw food without proper cooking can cause indigestion.
- Dehydrated food must be avoided as its nutritional property is already lost. The moisture in such food is not present for freeze-drying.
- Food products such as bread, cake, or other food based on yeast are not good for freeze-drying. These items should be consumed fresh as their texture and taste depend highly on their freshness.
3.3. Things to Remember
If you want to freeze dry foods, you must keep a few points in mind so that freeze drying process is properly done and can keep food safe for at least a week. If not done properly, it can ruin the food.
Freeze-drying food works best on fresh and ripped food with high value. You should ensure the moisture content in the food. Here are a few things you need to check before you freeze dry food:
- Only fully ripped fruits that are available in the season should be freeze-dried. Raw fruits, although high in moisture and can be freeze-dried, the taste will not be as good.
- Meat, fish, and other non-veg foods should be frozen instantly after cooking and cooling. Keeping freeze-dried meat out for too long will not only make the consistency of the cooked products thicker but will also burn down most of the nutrition.
- You should not store food for longer before freeze-drying as it will ruin the taste. Make sure to freeze dry food after cooking and after it cools.
- To enhance its shelf life, if you are preserving food raw such as meat or fish, then this frozen food must be cooked before consumption. Raw meat and uncooked food can cause indigestion and other digestive problems.
4. What Are The Food Preserving Methods
There are many different ways to preserve food with freeze-drying techniques. You can opt for any of these suitable methods at your convenience. Here are some of the most widely used food preservation methods:
4.1. How To Freeze Dry Food By Creating a Vacuum Chamber
This freezing process is suitable and commercially used in preserving food as the vacuum process inhibits the outgrowth of bacteria on the food. The dried food is safe and good for consumption. You can use a vacuum pump which creates a vacuum chamber.
4.1.1. How to freeze dry food
You can follow these simple steps for freezing food using a vacuum chamber:
- Cut the food or fruit you want to freeze dry. This will ensure every part will be properly freeze-dried.
- Spread the food slices on a tray or a plate so that the slices do not clamp together.
- Place the food tray in the vacuum chamber that you have made using the vacuum pump at about 120 m Torr and close the chamber.
- Set the temperature of the vacuum chamber to 10 degree Celsius.
The process of sublimation will not take more than a week to freeze dry completely. After a week, check out the slices to see if they have completely freeze-dried.
4.1.2. Points to Remember
- Ensure you do not open the chamber frequently, which will slow down the entire process.
- If you have a deep freezer at your home, you can use that with the lowest temperature.
You can store food in air-tight containers so the freeze-dried food can last longer.
4.2. How to Freeze Dry Food at Home Using a Freeze Dryer
Do you not have a vacuum pump or a chamber at home? Do not worry. You do not even need to have a freeze-drying machine. We have other methods that you can use for freeze-drying food at home.
We all are equipped with different types of appliances in our homes. A refrigerator is one such appliance. Most of us use the refrigerator for storing food and fruits for a few days. But do you know you can use the same refrigerator to freeze dry food?
Here is all that you need to know about freeze-drying at home. The refrigerator has a deep freezer chamber. Follow these simple steps to get freeze-dried food at home.
- Slice the food before freeze-drying.
- Place the food in a tray or plate, so the slices do not cluster together, forming a lump or loath.
- Keep the tray in the freezer for freeze-drying. Make sure that there is no other food in the freeze-dryer that you do not want freeze-dried.
- You should ideally keep the food in a freeze dryer for several weeks as the sublimation process takes time to complete.
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4.2.1. Things to remember
While your freeze-dried foods are in the process of making, you should keep in mind not to open the freezer frequently. Here are a few steps you are supposed to follow when you are using freeze-drying at home.
- Do not unnecessarily open the home freeze dryer as it will sl, ow down the freezing process. This will take some more days for the food to freeze dry completely.
- Opening the home freezer repeatedly will make ice crystals on the food, reducing the freeze-dried food’s quality.
- Take out a small piece of food to check if it has completely freeze-dried or not. When you take out the food piece, ensure it does not turn black after it melts, as this is the mark of food not completely freeze-dried.
- After the process is complete, you should store the freeze-dried food in freezer bags so that they can stay for a long time. You should push the air out of the bag so that moisture can not enter the food.
4.3. How to Freeze Dry Food With Dry Ice
This method involves the use of dry ice for freeze-drying at home. You can cut the food into small chunks and put them in the freezer bags before keeping them with dry ice at home freeze. If you do not have a freezer bag, you can also use a plastic bag. Make sure the plastic bag is airtight. Dry ice works well on any tightly sealed bag.
You can follow these steps after that:
- Keep the freezer bags flat, as keeping them vertically will collect the food in one part.
- Push the air out of the bag before sealing them close. Airtight bags ensure no moisture gets into the dried food or fruit.
- Place the food in the large Styrofoam cooler and completely cover it with dry ice. Leave the cooler to freeze dry.
- Keep the cooler in the freezer, and cover the cooler loosely with a lid.
- If the dry ice is not present in the cooler after 24 hours, it means it has done its work, and your freeze-dried food is ready.
4.3.1. Points to remember:
- Dry ice is a risky thing to handle. Wear gloves and a full-sleeved cloth before touching or using dry ice.
- Make sure not to tightly cover the cooler as the dry ice sublimes into gas that can store in and cause an explosion.
Dry ice is a solid form of carbon dioxide and can be a serious threat if not kept in a well-ventilated place. Using dry ice to freeze dry food and fruit can reduce electricity costs to about half the usual freeze-drying methods involving a freeze-dryer.
The freeze dry food with dry ice is safe for consumption. However, dried fruit still tastes the same, so it can be consumed as it is. All you need is to remember not to eat raw food.
5. Other Options
If you want to make your freeze-dried products with a home freezer, you can buy commercially freeze-dried food that uses pressure canning from the market. You can also use dry ice and make your freeze-dried food.
Freeze drying is a food preservation technique that keeps the food for longer use while maintaining the nutrition and flavor of the edible product.
6. How Is the Freeze-Drying Process Better than Simple Freezing?
When you store food in a refrigerator, it remains intact for a few weeks only. You can not keep the freeze-dried food for longer as it will rot, and you will have to discard it. However, when you freeze dry food, you can store it for as long as you want, lasting for years. Thawing the freeze-dried food is easy by putting it in boiling water before cooking.