As humans, we are always looking for the best option. Whether it is searching for the best method of communication (letters then stationary phones then iPhones), or the best way to travel (horse and buggy then into cars then Teslas), we are always looking to improve. Food preservation is no different. For years, humans have improved upon our methods of food preservation. Freeze-drying is the best method.
What it is?
In simple words, freeze-drying is a process in which water is removed from a frozen material to preserve it for a longer time via a process of sublimation, which is the direct conversion of solid to vapor state without passing into a liquid state.
Also termed as lyophilization, it is the process of dehydrating a product by reducing its surrounding pressure to sublime the frozen material to extend its shelf life. It is a three-step process that is as follows.
- Primary Drying (Sublimation)
- Secondary Drying (Adsorption)
This preserving technique was first developed by the indigenous people of Peru to freeze tubers and potatoes at the top of the Andes Mountains, where they allowed potatoes to freeze in cold nights and evaporated the ice in the sun to extend the food life.
They also formed a powder named chuno from these potatoes and used it in stews and baking. The Japanese also preserved tofu by using the same technique. Northern Europe Vikings also used the same freezing technique to preserve the codfish and other related food items.
These early attempts to freeze-dry products worked, but the method was not that consistent unless, in 1890, a tissue was perfectly dried and rehydrated in the lab successfully.
Later in World War II, freeze-drying process-preserved plasma, made it light to be transported, rehydrated without degradation; and plasma was transported to and from hospitals easily.
Soon, the technique gained popularity. In 1965, Nestle released its first freeze-dried product, Nescafe gold blend-the instant freeze-dried coffee. Since, scientists have pushed boundaries and used this freeze-drying technique for vast applications.
Applications of Freeze-Drying
Freeze-drying has numerous applications, such as:
- Pharmaceuticals and biotechnology
- Raw-materials- it is used in the production of bulk raw materials to keep them chemically stable over the years.
- Food processing industry
- Archaeological recovery and conservation
- And many others.
How it works?
Let us introduce you to the freeze-drying process. As stated earlier, this process is a three-step technique of dehydrating a product to extend its life.
Freezing is the first step. It is done in a chiller, freeze-drying machines, or shell freezer. The product is cooled below its eutectic point (solid and liquid phase coexist at this point), which is the lowest temperature at which sublimation occurs.
Freezing is done quickly for biological materials whose crystals tend to break the cell walls. However, for materials that tend to precipitate, annealing, or slow freezing is used.
Freezing is critical to prevent the product from spoiling. Usually, the frozen product is cut down to the desired size, stacked evenly in the tray to store inside the freezer at even cold temperature to retain the product shape where the second step is initiated.
The second step is sublimation or the primary drying. In this step, the product is present in the freeze-drying chamber, where pressure is lowered, and the chamber’s vacuum system adds heat to removes ice from the product to sublime it. This step removes about 95% of the water in the product.
The third step is adsorption or secondary drying. Temperature is raised higher than primary drying to a point to break the chemical bond between water molecules and the frozen material to dry it. Only 1 to 5% of residual moisture will remain in the product. Before sealing the material, the vacuum is broken with an inert gas after freeze-drying is complete.
Benefits of freeze-drying
The process removes moisture content from the products to preserve them for a longer time. The shelf life is increased, and you can preserve the food items for a longer time. Let us review some amazing benefits of this technique:
1. The safest method of preservation
The freeze-drying method is safe and healthier than other preserving techniques. It retains the shape and the vital nutrients of the products much better than other drying methods. The structure, texture, and appearance remain intact during this method of preserving.
2. Pro-longed preservation
Freeze-dried products have an extended shelf life. You can store freeze-dried fruits, vegetables, and meats for longer average shelf life. Freeze-dried food remains fresh for years.
3. Taste, color, and nutrition retention
Freeze-dried products retain the color, taste, and nutritional values for quite a long time. The food is preserved at the peak of ripeness and nutritional content, and freeze-drying preserves all nutrition.
Freeze-drying halts the degradation of vital vitamins and keeps them intact such as Vitamin A (which has an important role in the health of your eyes, bones, and immune system) along with vitamin C that is also very beneficial for human health. This technique also preserves nutrients and probiotics in dairy products.
Please note that nutrition is an important selling point. Today, customers are always looking for the healthier option. This makes freeze-dried products very marketable. Some brands may even choose to sell at a premium because of this.
4. Easy Transportation
You freeze-dry the product, and it becomes light in weight and easy to be stored and transported. The light freeze-dried products are easy to pack. With proper packing, freeze-dried products can travel long miles without getting deformed or worn out.
5. Freeze-drying makes food more palatable and easy to prepare
Some products, after freeze-drying, develop a more pleasant taste. They are easy to prepare, too; just add water, and your food will be ready and fresh for eating.
To discuss how freeze-drying can be beneficial to you, contact Empire Freezing & Drying at firstname.lastname@example.org or 973-649-9800