Freeze dried foods are those that have undergone the process of lyophilization, or freeze drying, which allows them to have a vastly longer shelf life while at the same time retaining most of the nutrients. Studies of nutrient retention in freeze dried foods, specifically freeze dried fruits, have already been supported by the American Institute for Cancer Research (AICR). Freeze drying foods involve removing water from frozen food, and commercially produced packets and tins of freeze dried foods require rehydration first before consumption. The removal of water makes freeze dried foods lightweight and convenient for travel and especially long term storage as emergency supplies.
The primary purpose of freeze drying within the food industry is to extend the shelf-life of the food while maintaining the quality.Freeze-drying is known to result in the highest quality of foods amongst all drying techniques because structural integrity is maintained along with preservation of flavors. Because freeze drying is expensive, it is used mainly with high-value products. Examples of high-value freeze-dried products are seasonal fruits and vegetables because of their limited availability, coffee, and foods used for military rations, astronauts/cosmonauts, and/or hikers。
What is freeze-dried food?
Freeze dried food is preserved through a flash frozen process. The food is then stored inside of either an airtight container or a vacuum pouch.
The moisture in freeze dried food dissipates far more rapidly during the preservation process than it does when being dehydrated.It is because of the rapid water removal that freeze dried food does not wind up with a sort of deforted shriveled look. Generally, freeze dried food will rehydrate far quicker than dehydrated food.
Freeze drying food is still in its infancy, when compared to dehydrating, smoking, and even canning. This food preservation method is believed to have first been used on a basic level, during the times of the Inca empire.It was not until the World War II when the United States Military learned how to use freeze drying to preserve medicine, plasma, and ultimately food, for the troops. That’s when it became a more commonplace method of food preservation.
Even though a machine is generally required to freeze dry food, the process is no more complicated than dehydration.The food being preserved is put on racks inside of the machine’s vacuum chamber, then the temperature is quickly lowered to below 32 degrees, and then slowly raised back up above freezing.
Home freeze drying ovens hit the marketplace several years ago, and have come down in cost a little bit since then – but not much. Purchasing such a machine will still run you around $2,000 to $4,500, depending on capacity.
Although there is a high upfront cost associated with this method, in the long run it is typically far more economical an option than purchasing long-term food storage buckets…at least if you grow and raise a significant part of your own groceries.
How Freeze Drying Works
Freeze drying is the process of dehydrating frozen foods under a vacuum so the moisture content changes directly from a solid to a gaseous form without having to undergo the intermediate liquid state through sublimation. In this process, freeze dried food maintains its original size and shape with a minimum of cell rupture. Removing moisture prevents a product from deteriorating at room temperature.
Simply put, freeze-drying is the removal of water from a frozen product using a process called sublimation. Sublimation occurs when a frozen liquid transforms directly to a gaseous state without passing back through the liquid phase. The process of freeze-drying consists of three phases: prefreezing, primary drying, and secondary drying.
Freeze dried food must first be prefrozen below its eutectic temperature, or simply put, freezing the materials (solute) that make up the food. Although a product may appear to be frozen because of all the ice that is present, in actuality it is not completely frozen until all of the solute is frozen as well.
After prefreezing, ice must be removed from the product through sublimation. This requires careful control of two parameters; temperature and pressure. The rate of sublimation depends on the difference in vapor pressure of the product compared to the vapor pressure of the ice collector. Molecules move from the higher pressure sample to the lower pressure sample. Since vapor pressure is related to temperature, it is also necessary for the product temperature to be warmer than the ice collector temperature.
After primary drying, all ice has sublimated but some liquid is still present in the product. Continued drying is necessary to remove the remaining water. The process for removing this excess water is called isothermal desorption. The excess water is desorbed from the product by making the product temperature higher than the ambient temperature.
During the entire freeze-drying process, the exact freezing methodology and proper storage is very important.
What are the Benefits of Freeze Dried Foods?
Texture is one of the major benefits of freeze dried foods. Unlike dehydration, which changes the makeup of the food, freeze dried foods maintain the same texture as their fresh counterparts.
Think of it this way: a dehydrated grape is a raisin but a freeze dried grape, once rehydrated is just like a fresh grape.
We frequently rehydrate freeze dried raspberries and everyone is shocked that they look so close to a fresh raspberry. The benefit of this is that you can use freeze dried foods almost the same way you would use fresh, which makes it really easy to add them into your regular recipes.
Freeze dried foods retain all their nutrients whereas dehydrated foods often lose up to 50% of their nutrients because they are heated as they are dried. In many cases, this makes freeze dried foods a healthier choice than fresh foods from the grocery store since produce generally takes several days to transport to the store and may sit on the shelve for several days after that. The longer fresh food sits, the more nutrients it loses.
Freeze dried foods are picked at the peak of freshness and flash frozen right away so they maintain their nutrients. We store Thrive freeze dried foods and they are known for their quality.
Many consumers wonder what the difference is in terms of taste when it comes to freeze dried and dehydrated snacks. Dehydrated foods can lose much of their flavor, mainly due to the heat drying processes used to remove the moisture. Freeze dried foods (including fruits!) keep most of their original flavor until they are ready to be enjoyed.
Additional Benefits of Freeze Dried Foods
Shelf Life – Because of the lower moisture content in freeze dried foods, they have a longer shelf life than dehydrated. That’s great news when you are adding them to your long-term food storage.
Free of Additives – I love looking at the ingredient list of freeze dried foods because they contain only one thing! Freeze dried foods don’t require any additives whereas dehydrated foods often require sugar, salt, or other preservatives.
Nearly anything can be freeze dried – I love how many different products I can keep in my long-term food storage with freeze dried foods. my long-term food storage looks a lot like my regular pantry — which is probably why they have become so integrated! We even have freeze dried ice-cream sandwiches in our long-term food storage because if we are ever in a true emergency situation you know I’m going to want something chocolate.
Shelf Life Of Freeze Dried Food
The biggest advantage of freeze-dried food is its shelf life. Freeze dried food lasts longer than canned/dehydrated food. It also tastes great and retains all the goodness in the process. Frozen food can last up to 2 years, canned food for up to 3 years and dehydrated food up to 4 years. The freeze dried foods you purchase in stores are sealed in resilient packaging under nitrogen and can last anywhere from 2-25 years. Unfortunately, freeze dried fruits are on the lower end of the shelf-life spectrum, and can last you for just 2 years.
Longevity of freeze dried depends on how you store it. Packaging is the only barrier between your freeze dried food and those elements that can make it go bad. Once you break the seal on a freeze dried food package, the shelf-life drastically reduces. This is especially true if you store the unpacked food in humid conditions. For most freeze dried foods, they are palatable for 6 months. You need to create a hostile environment for microorganisms to extend the expiry period.
How to Freeze Dry Food at Home?
You don’t need super-advanced techniques to freeze dry food. Here are 3 ways to end up with freeze dried food. Before you start though it’s recommended to have some good food storage containers on hand.
Method 1: Using Dry Ice
This method is the easiest but also a little dangerous. To keep yourself safe, always wear gloves and protective gear. The dry ice shouldn’t touch your skin directly.
Put your food of choice in a freezer-safe bag and try to get rid of as much air as you can. Also, distribute the food evenly and ensure that the food is not clumped.
Put the bag with food inside into a cooler. Slowly cover the bag with the dry ice (CO2). If you have multiple bags of food, consider layering them with the dry ice. Placing the dry ice between the food bags will keep them separate.
Place your cooler in a freezer and leave it uninterrupted with the lid on for about 6-8 hours. Dry ice lets all moisture evaporate from the food. Check back after 24 hours, and if the dry ice is gone, your food is successfully freeze dried!
Get rid of the bags and store them in a safe place, out of children’s reach.
Method 2: Using your Freezer
This a non-expensive method you can use to freeze dry food as you don’t have to purchase anything else. There is no more action on you your part than putting the food in the freezer and leaving it.
To use this method, first put all your food slices/chunks on a plate/tray. Ensure that they are separate to keep them from freeze drying in clumps.
Ensure there’s nothing else in the freezer. If you don’t own a deep freezer, you can use a standard freezer. Place the food in the bottom compartment and remember to set it to the coldest setting possible.
Carefully place the food tray in the freezer and leave it there for 7-10 days. DO NOT open up the freezer during the sublimation period as this can interfere with the freezing process and cause ice crystals to form on the food. Ice crystals will slow down the process.
But how do you know if the food is completely freeze dried? After about a week, take the tray with food out of the freezer, pick a piece and let it thaw. If it turns blackish in color, then it is not ready yet. You need to let it dry more.
Once you are certain that the food is freeze dried, store it in a vacuum-sealed bag. Ensure there is no air in the bags. Store them in a pantry, freezer or disaster preparedness kit.
Method 3: Using A Freeze Dryer
This is by far the simplest method of freeze drying food but it will need you to purchase a freeze drying appliance. They don’t come cheap but they’re a great investment. The process is similar in concept to the one above. When the vacuum chamber is set to 100C, it will take around 7 days to complete the sublimation process. The sublimation will depend on how much moisture is in the food. When the process is over, place the food in storage bags and seal them properly.
The Reasons Freeze Dryers are Becoming Increasingly Popular
There are several reasons why more and more people are going for freeze dryers. They include:
To Store Food for Survival and for Emergency Purposes
For quite a long time, freeze dryers were mostly associated with the military, campers, hunters, hikers, adventurers, and survivalists. The people listed above frequently used freeze dryers in the past to preserve food for survival in the wild.
However, nowadays freeze dryers are more widely accepted across the country. This is especially true in disaster-prone areas where disruptions to the food supply chains are frequent.
To Preserve Food for a Long Time
This is probably the number one reason behind the growing popularity of freeze dryers. Freeze-dried food has a shelf life of between 2 to 25 years depending on the type of food and packaging you’ve put it in. Some foods such as fruits can only last for as long as two years, and some packaging will let in air and moisture further reducing the preservation period.
It’s safe to say that the reason so many people are interested in freeze-dryers is because they preserve food for a very long time.
To Retain the Maximum Nutritional Value of Food
As mentioned earlier, freeze drying is one of the best methods of food preservation because it retains most of the nutrition. Recent research shows that the method retains approximately 97 percent of nutrients. In contrast, dehydration only retains 60 percent of nutrients while deep freezing retains even less nutrients.
Therefore, if you want your food to remain as nutritious as it is while fresh, freeze drying is the way to go especially if you are preserving it for long term storage.
To Store Dairy Products
Not many people would readily associate freeze drying with dairy products. However, the method of preservation is one of the best ones for the long term preservation of dairy products such as yogurt and cheese.
Freeze-dried yogurt can be rehydrated quickly when necessary or can be eaten as is without needing a spoon or cup. Freeze-dried cheese, on the other hand, can also be quickly rehydrated to return to its original state.
The best thing about preserving such dairy products by freeze drying is that the process preserves both nutrients and probiotics.
For Quick Meals
Frozen foods take a lot of time to thaw before they can be prepared. Dehydrated foods may also need some time to cook while freeze-dried foods are usually very easy to prepare. Some freeze-dried foods only need to be put in warm water for a couple of minutes and they will be ready to enjoy.
So if you want to store food in such a way that will allow you to prepare quick meals when the time comes, choose freeze drying.
To Use Real Food Products For a Variety of Applications
Freeze drying allows you to use real fruits, vegetables, meats, and cereals in a variety applications. For example, freeze-dried fruits can be used to make ready-to-eat cereals and snacks. They can also be used to make smoothies. Freeze-dried meats can be used to make soup dishes or to make delicious protein-rich meals.
To Save Pantry Space and to Prevent Waste
When you freeze dry food, you will not need big jars to store it. Vacuum-sealed Mylar bags will do the job. This means you can save your pantry space to store other types of food.