freeze-drying

Freeze Drying: Consider This (4 of 4 in this series)

Best Practices: Start with the end in mind

Freeze-dried food has entered the home food preservation scene! Domestic freeze dryers have been introduced to homeowners within the past 10 years.  More preservation enthusiasts have ventured into this form of food preservation.  Once a machine has been chosen and placed in your home, there are a few things that you should keep in mind for the best results for your family. 

As with any food preservation method, be sure you start with decent quality food. The better quality of food you use, the better results you will achieve when freeze drying your food.   

Often, we think of food preservation as a means of saving food for an extended period of time, with freeze-drying extending that time beyond other methods. Freeze drying is effective for preserving your garden as well as preparing for possible food shortages or natural disasters. Freeze-drying can offer short-term benefits for immediate enjoyment as well. Fruit freeze-dried today can be enjoyed as a snack tomorrow. Leftover meals can be freeze-dried for a quick family dinner on a busy night or preserved for a camping or hiking trip in the coming months. Garden herbs and vegetables can be freeze-dried and used in recipes for meals throughout the year.  

Five jars containing freeze dried vegetables, meats and seasonings.

The process of freeze-drying food has minimal preparation, the processing time may be longer but does not require constant attention, and food may be immediately packaged from the freeze dryer for short-term or long-term storage. While the steps may be simple, there are several tips to make this process more effective.  

Consider these tips:  

  • Freeze-drying times are not a fixed number. The amount of product on the tray will impact the processing time, but the good news is that the freeze dryer will adjust without human intervention. 
  • Uniformly prepared food pieces optimize drying time. When placing trays into the freeze-dryer, place denser items in the center for the best results. 
  • The higher the water content in the food, the longer the processing time. Pre-freezing the food may help reduce processing time.    
  • A warmer room temperature will increase the processing time.   
  • Almost all foods can be freeze-dried, but for the best results, avoid oily foods including butter, peanut butter, and chocolate. Also, for more success, refrain from using honey, syrup, and jam. 
  • Be certain to label your jars and bags as “raw” if you have freeze-dried any uncooked beef, poultry, fish, pork, or eggs, don’t assume the freeze-drying process makes your food bacteria-free.  Raw meat should be used right away because freeze-drying does not kill bacteria.  
  • Freeze-drying is not considered cottage food.  

Track your journey 

While freeze-drying is not an exact science, it is recommended to keep a journal of all your successes and lessons learned. Keep track of what works for you and your family and document your freeze-drying journey! For more information on freeze-drying, check out the Freeze-Drying: Consider This blog series.  

 Resources: 

Utah State University: https://extension.usu.edu/preserve-the-harvest/research/buying-a-home-freeze-dryer-what-to-know-before-you-go   

https://harvestright.com/wp-content/uploads/2019/09/GUIDE-TO-FREEZE-DRYING.pdf (retrieved on 11-2-2023) 

Melanie Hausch, food preservationist and subject matter expert, Bryan, Ohio  

Written by: 

Emma Horstman, Extension Educator, Ohio State University Extension, Paulding County 

Melissa J. Rupp, Extension Educator, Ohio State University Extension, Fulton County 

Reviewed by: 

 Ohio State University Extension, Food Preservation Team  

Photo Credit:  

Laura Halladay, Extension Educator, Ohio State University Extension, Greene County.  

Freeze Drying: Consider This (4 of 4 in this series) 

Best Practices: Start with the end in mind

Freeze-dried food has entered the home food preservation scene! Domestic freeze dryers have been introduced to homeowners within the past 10 years.  More preservation enthusiasts have ventured into this form of food preservation.  Once a machine has been chosen and placed in your home, there are a few things that you should keep in mind for the best results for your family. 

As with any food preservation method, be sure you start with decent quality food. The better quality of food you use, the better results you will achieve when freeze drying your food.   

Often, we think of food preservation as a means of saving food for an extended period of time, with freeze-drying extending that time beyond other methods. Freeze drying is effective for preserving your garden as well as preparing for possible food shortages or natural disasters. Freeze-drying can offer short-term benefits for immediate enjoyment as well. Fruit freeze-dried today can be enjoyed as a snack tomorrow. Leftover meals can be freeze-dried for a quick family dinner on a busy night or preserved for a camping or hiking trip in the coming months. Garden herbs and vegetables can be freeze-dried and used in recipes for meals throughout the year.  

Five jars containing freeze dried vegetables, meats and seasonings.

The process of freeze-drying food has minimal preparation, the processing time may be longer but does not require constant attention, and food may be immediately packaged from the freeze dryer for short-term or long-term storage. While the steps may be simple, there are several tips to make this process more effective.  

Consider these tips:  

  • Freeze-drying times are not a fixed number. The amount of product on the tray will impact the processing time, but the good news is that the freeze dryer will adjust without human intervention. 
  • Uniformly prepared food pieces optimize drying time. When placing trays into the freeze-dryer, place denser items in the center for the best results. 
  • The higher the water content in the food, the longer the processing time. Pre-freezing the food may help reduce processing time.    
  • A warmer room temperature will increase the processing time.   
  • Almost all foods can be freeze-dried, but for the best results, avoid oily foods including butter, peanut butter, and chocolate. Also, for more success, refrain from using honey, syrup, and jam. 
  • Be certain to label your jars and bags as “raw” if you have freeze-dried any uncooked beef, poultry, fish, pork, or eggs, don’t assume the freeze-drying process makes your food bacteria-free.  Raw meat should be used right away because freeze-drying does not kill bacteria.  
  • Freeze-drying is not considered cottage food.  

Track your journey 

While freeze-drying is not an exact science, it is recommended to keep a journal of all your successes and lessons learned. Keep track of what works for you and your family and document your freeze-drying journey! For more information on freeze-drying, check out the Freeze-Drying: Consider This blog series.  

 Resources: 

Utah State University: https://extension.usu.edu/preserve-the-harvest/research/buying-a-home-freeze-dryer-what-to-know-before-you-go   

https://harvestright.com/wp-content/uploads/2019/09/GUIDE-TO-FREEZE-DRYING.pdf (retrieved on 11-2-2023) 

Melanie Hausch, food preservationist and subject matter expert, Bryan, Ohio  

Written by: 

Emma Horstman, Extension Educator, Ohio State University Extension, Paulding County 

Melissa J. Rupp, Extension Educator, Ohio State University Extension, Fulton County 

Reviewed by: 

 Ohio State University Extension, Food Preservation Team  

Photo Credit:  

Laura Halladay, Extension Educator, Ohio State University Extension, Greene County.  

Freeze-Drying: Consider This – Keep the Good Stuff, Lose the Water

Good reasons to freeze-dry 

Freeze-drying has long been used by outdoor enthusiasts for lightweight snacks and complete meals on the trail; but did you know freeze-dried foods are also great for quick and healthy snacks, traveling, easy meal preparation, emergency preparedness, and even homemade pet food.  

Freeze-drying is a terrific way to reduce food waste and preserve the harvest. You may be asking “What types of food can I freeze-dry?” Fruits, vegetables, meats, dairy products, desserts, and complete meals can all be effectively freeze-dried. 

freeze drying veggies

Good Health 

Freeze-drying is a food preservation process, not a food safety process. It will not make unsafe foods safe. It is important to remember that freeze-drying does not destroy enzymes or microorganisms. Enzymes are less active but are still present and can lead to reduced food quality over time. If the goal is long-term storage, consider blanching vegetables and treating fruit that is prone to browning. Microorganisms will become inactive but are not killed.  

If raw, fresh produce is contaminated, those same contaminants will be on the food when it is eaten. Special considerations must be made when eating freeze-dried animal products that have not been cooked (eggs, meats, poultry). These foods should be labeled “raw” and must be heat treated prior to consuming. 

Good Nutrition 

Color, flavor, shape and approximately 90% of the nutritional value of the food are maintained. The freezing process occurs very quickly thus reducing nutrient loss and retaining food quality. The drying process allows the food to be lightweight and shelf stable. While food weight is reduced, the volume of food may not be reduced. Many items retain their shape when freeze-dried. An exception is high-water content liquid items like soup, milk, and eggs which become crumbly and powder-like. These foods are often rehydrated back to their original volume before being consumed.  

The calorie content by volume may be similar to the original food item for products that retain their shape, or it may be higher for foods that crumble or become powders. Additionally, salt and sugar become more concentrated, so salty foods will taste saltier and sweet foods will taste sweeter. The vitamin and mineral content will be unchanged. You may need to increase your fluid intake when consuming freeze-dried foods. 

Please note that freeze-dried foods are not allowed as cottage foods in Ohio. 

These are just a few things to consider as you explore freeze-drying. It is up to you to determine the benefits and drawbacks for you and your family. Please read each of the Freeze-drying: Consider This blog articles for more information! 

Freeze-Drying: Consider This 

Freeze-Drying: Consider This – Food Dehydration, Freezing, and Freeze-drying 

Stay tuned for the final article in the series! 

Resources: 

Bhatta S, Stevanovic Janezic T, Ratti C. Freeze-Drying of Plant-Based Foods. Foods. 2020 Jan 13;9(1):87. 

Geiger, M. Iowa State University Extension Preserving by Home Freeze Drying Blog. 2023 June 13. https://blogs.extension.iastate.edu/answerline/2023/06/13/preserving-by-home-freeze-drying/  

Kupletskaya, M.B., Netrusov, A.I. Viability of lyophilized microorganisms after 50-year storage. Microbiology. 2011; 80 (6): 850.  

Yukie Miyamoto-Shinohara, Takashi Imaizumi, Junji Sukenobe, Yukie Murakami, Sugio Kawamura, Yasuhiko Komatsu, Survival Rate of Microbes after Freeze-Drying and Long-Term Storage. Cryobiology. 2000 Nov; 41(3):251. 

Written by: 

Christine Kendle, Extension Educator, Ohio State University Extension, Tuscarawas County and Kate Shumaker, Extension Educator, Ohio State University Extension, Holmes County. 

Assisted by Tiffany Haney, Intern, Stark State University Dietetic Technician Program. 

Reviewed by: Ohio State University Extension, Food Preservation Team. 

Photo Credit: Laura Halladay, Ohio State University Extension, Greene County 

Freeze-Drying: Consider This

What is the difference? Food Dehydration, Freezing, and Freeze-Drying 

Freeze-dried food in jars

Have you ever wondered the difference between dehydration, freezing, and freeze-drying food?

One of the oldest methods of preserving food for long-term storage is drying or dehydration. Later, with the invention of electricity, we incorporated refrigeration and freezing, with freezing as another method for long-term food storage. Today, freeze-drying is growing in popularity as the “newest” long-term food choice alongside dehydration, freezing, and other familiar practices like canning. What we would like to discuss is the difference between dehydrated, frozen, and freeze-drying as they relate to long-term food storage. 

In some cases, it can seem remarkably similar, by design or marketing, that drying, freezing, and freeze drying are all the same in processing, packaging, and longevity. However, there are key differences.  

Drying or dehydration is the mechanical method of removing water and moisture content from solid food through the application of heat, varying between 90°-140° Fahrenheit and according to processing recommendations. When deciding the method of drying or dehydration, a food-grade dehydrator is the most common equipment used. As with any form of food preservation, storage is a factor to consider before starting. After processing, dried, or dehydrated food should be allowed to cool for 30-60 minutes, then packed loosely in food-grade containers, sealed tightly, and stored in a clean, cool, dry, dark space. 

Freezing is the preserving of food by lowering the temperature to inhibit microbial growth, with best results below temperatures of 0° Fahrenheit, -18° Celsius. You need to consider the space and location when choosing freezing as your storage method. Most refrigerators will include a freezer section, but in most cases, those preserving with this method will buy a standalone deep freezer to increase storage ability. You also need to consider your electrical wattage ability depending on the size of your unit. For the best quality freeze food as quickly as possible and allow head space when storing in freezer-grade packaging to allow for food expansion during the freezing process.  

Freeze dryer machine

Freeze-Drying (Lyophilization) is the mechanical method where extreme cold is applied rapidly to food between -30° Fahrenheit and -50° Fahrenheit. At this point, the machine introduces slight heat to produce water vapors, a process called sublimation. These water vapors are removed through a powerful vacuum pump system. Freeze-drying can only be completed with a manufactured home or commercial freeze-drying unit. After your system has completed the automated cycle, remove the food from trays and store in approved food-grade Mylar® bags or glass jars. Packaging should include proper single-use oxygen absorbers to ensure the best quality and increase shelf life. As with all long-term storage, food should be stored in a clean, cool, dry, dark location.  

In summary, consideration should be made for need, cost, space, and location when choosing any long-term food storage practice, and always source reliable accredited information. 

Stay tuned for more information on our Freeze-Drying: Consider This blog series.   

References 

Herringshaw. (2015). Drying fruits and vegetables. Ohioline. https://ohioline.osu.edu/factsheet/HYG-5347 
Herringshaw. (2015). Food preservation: Freezing basics. Ohioline. https://ohioline.osu.edu/factsheet/hyg-5341 
Hirneisen, A., & McGeehan, N. (2023, May 24). Let’s preserve: Freeze-drying. Penn State Extension. https://extension.psu.edu/lets-preserve-freeze-drying 

Written by:  

Sofia Carter, Family and Consumer Sciences Educator, The Ohio State University Extension, Champaign County, and 
Laura Halladay, Family and Consumer Sciences Educator, The Ohio State University Extension, Greene County. 

Reviewed by: Ohio State University Extension, Food Preservation Team.  

Photo credit: Laura Halladay, Extension Educator, The Ohio State University Extension, Greene County. 

Freeze-Drying: Consider This 

freeze-dried vegetables in jar with oxygen absorbersDo you want to reduce your food waste? Would you like to have shelf stable foods in case of emergency? Do you like to prepare healthy snacks? Do you enjoy camping, hiking, or hunting? If you answered yes to one or all these questions, freeze drying may be for you!  

What is Freeze-Drying? 

According to the FDA: “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)”. Through the process of sublimation, many of the food products retain their original texture, flavor, and nutrients once reconstituted.  

What Can Be Freeze-Dried 

Almost any food can be freeze-dried. The foods that work best with freeze-drying are: 

  • Fruits 
  • Vegetables 
  • Dairy foods including cheese, milk, yogurt, ice cream 
  • Proteins including poultry, seafood, red meat, eggs 
  • Mixed foods including casserole, soup, lasagna, quiche 

Foods that do not freeze-dry well: 

  • Foods high in fat content 
  • Foods high in sugar content 
  • Baked goods including breads, muffins, cake 

Storing Freeze-Dried Foods 

Once you have a freeze-dried product, storage becomes a consideration. Iowa State University suggests, “The storage container must eliminate oxygen, light, and moisture. In order of long-term to short-term storage, the following containers may be used: Mylar® bags, vacuum-sealed canning jars, #10 cans, vacuum sealed bags, and PETE re-sealable containers”. PETE bags and glass Mason-type jars are the most readily available storage options. If you wonder what PETE 

pete mylar food storage bag

bags are, they are made of polyethylene terephthalate, a food grade, non-toxic, and typically opaque silver pouch. For long term storage,  oxygen absorbers are required. Oxygen absorbers are materials in a pouch that removes oxygen from space around food particles. Oxygen absorbers extend the shelf life of products by preventing color change and reducing the growth of microorganisms. While this term may be new to you, you have seen them in purchased items like baked goods, cheeses, pet foods, and seasonings. Freeze-dried foods that will be stored for no more than a few months (for example, fruits that you plan to snack on soon), can be stored in food storage containers or Mason-type jars without oxygen absorbers. 

Oxygen absorbers can be found in many sizes varying from 20cc to 2000cc. (The “cc” stands for cubic centimeters as it related to amount of oxygen absorbing capacity). According to Utah State University, “A quart container will need one 50cc, a gallon container and #10 can will need 300cc of oxygen absorption and a 5-gallon container will need three of the 500cc packet”. Once purchased, oxygen absorbers should be used within 6 months to 1 year. Store unused oxygen absorbers in an airtight glass jar for up to 6 months.  

Overall Safety of Freeze-Dried Food 

For the highest quality, all home preserved foods should be stored in a cool, dry location. This includes foods that are home canned, dehydrated, and freeze dried. Labeling is even more important for freeze-dried foods because you cannot see what is in your PETE pouch. Always include date, preparation method (raw or cooked), product name, amount (for some foods like soup), and directions or notes, for example, how a tomato is sliced, or how a food is seasoned.  

While freeze drying can sound exciting, there is a financial investment to get started. The cost range to purchase a home freeze dryer is between $2,000 and $6,000. Other considerations are machine location, supplies for storage, electric use, noise, temperature, accessories, and time needed to complete the process. Stay tuned for more information on the Freeze-Drying: Consider This blog series.  

Resources: 

Utah State University: https://extension.usu.edu/preserve-the-harvest/research/buying-a-home-freeze-dryer-what-to-know-before-you-go 

Iowa State University Extension and Outreach: https://blogs.extension.iastate.edu/answerline/2023/06/13/preserving-by-home-freeze-drying/ 

Written by:  Lisa Barlage, Extension Educator, Ohio State University Extension, Ross County and Megan Taylor, Extension Educator, Ohio State University Extension, Union County. 

Reviewed by: Ohio State University Extension, Food Preservation Team. 

Photo credit: Laura Halladay, Extension Educator, Ohio State University Extension, Greene County.