Freeze-drying, or lyophilization, is the removal of water from frozen food through a process called sublimation.This process is done under a vacuum and low temperatures, and the product freezing solidly during the process.
Freeze drying removes water from the food to make it last longer. The water’s vaporized through the process of sublimation, where water, in solid state, changes directly to vapor, producing a product with controllable moisture. It’s a perfect way to preserve food, since freeze dried food products don’t shrink.Freeze dried foods can be stored without cooking or refrigeration. They need no additional flavor or color modification. Freeze dried foods are also light and are ideal for space travel, camping, backpacking, and traveling.
The History of Freeze-Drying
Freeze-drying might seem like a futuristic food preservation technique, and while the technology we use today is much more advanced, the concept of preserving food with pressure and temperature has a long, interesting history. Freeze-drying doesn’t add sugar, sulfites, or other preservatives to food, but it can still create delicious shelf-stable products. And it has for many years.
Discover the history of freeze-drying and learn how far we’ve come in safe food preservation.
Freeze-drying developed separately in early communities in the Americas, Eastern Asia, and Northern Europe. Peru was the first region, with local indigenous peoples freezing tubers and potatoes atop the chilly Andes mountains. They’d set their frozen goods in the summer sun, allowing the ice to evaporate. “Chuño” was a staple in their diet, and was formed by grinding these preserved potatoes into a fine powder. It was used primarily in stews and baking. This method kept the indigenous communities fed year-round, with safely preserved food that tasted good too.
Hundreds of years ago, Japanese monks just south of Osaka on Mount Koya developed a similar process for preserving tofu. To make “koyadofu,” bean curd was packed into the snowy mountainside where low temperatures and atmospheric pressure — thanks to the high altitude — evaporated water in the tofu quickly.
Vikings in Northern Europe used similar techniques to preserve codfish, only they built triangular wooden racks that enabled them to create larger quantities of preserved food. This early method of freeze-drying in bulk preserved fish for up to two years — an incredible discovery for this early population.
Innovations in science
These early attempts at freeze-drying were vastly less sophisticated and less consistent compared to the cutting-edge freeze-drying methods used today. In fact, freeze-drying techniques weren’t successfully used in a lab until 1890, when tissue was perfectly dried and rehydrated for the first time. Even then, it took decades of development before the science was ready to be used on a wide scale.
In World War II, freeze-drying was used to transport plasma to and from hospitals in Europe. Freeze-drying safely preserved blood plasma, made it light enough for travel, and it was easy to rehydrate without quality degradation. Soon after, the technique was perfected and used as a way to preserve and transport vaccines — a method that’s still used today.
Many food brands were already hard at work trying to develop new food products with freeze-drying technology. In 1965, Nestlé released Nescafé Gold Blend, the first freeze-dried instant coffee. Over the next few years, freeze-drying would produce a whole slew of new foods, many of which (including freeze-dried ice cream) famously launched into space aboard Gemini in 1965 and Apollo 7 in 1968.
Freeze-drying has come a long way since the early Peruvians froze their potatoes. Here at Mercer, we’re proud to be a part of that storied history. With improved technology and scientific testing, Mercer is pushing the boundaries of freeze-dried foods to create better and more consistent results. With new products and innovative uses for preserved foods, the future of freeze-drying is bright!
Commercial Applications in Food Processing
The global freeze-dried food market is growing at 7.4% a year, according to Mordor Intelligence, and the U.S. market is expected to reach $66.5 billion by 2021. Fruits comprise the largest portion of the global freeze-dried food market, holding a 32% share. In addition, North America has the largest share of the global freeze-dried market, holding a 35% share. South America and Asia-Pacific are the fastest-growing markets.
Some foods freeze-dry very well, but not all food is suitable for freeze-drying. Freeze-drying is commonly used for coffee, fruit, juice, vegetables, herbs, food flavorings, fish, seafood, eggs, and dairy. Individual food types can be freeze-dried, as can dishes with multiple ingredients, such as stews or soups. As a result, freeze-dried foods can be used for backpacking, camping, military rations, survival food storage, and space exploration. Generally, larger-sized foods (such as fruit or meat) need to be cut into smaller pieces prior to freeze-drying. Thermally sensitive materials, such as fruits, are good candidates for freeze-drying. These have become popular as snacks and ingredients in other foods, such as breakfast cereals. Meat and seafood require cooking before freeze-drying. For some foods, freeze-drying is not cost-effective.
The cost of freeze-drying remains the greatest challenge around increased commercial implementation of this remarkable technology. Future advances will likely focus on this challenge. Pretreatments are one approach to reducing costs. Pretreatments, such as osmotic dehydration, ultrasound treatment, and infrared heating, have all shown potential to save energy and cost. In addition, final product quality can be improved through infrared pretreatment. Replacement of the heating source with microwaves or use of spray nozzles in the drying chamber also offer promise to reduce the cost of freeze-drying. Advances in these areas are expected to support a solid future for freeze-drying.