What is freeze drying?
Freeze drying is a process that removes water from food by freezing it and then reducing the surrounding pressure to cause the water to sublimate (skip the liquid phase). It’s essentially the same process your refrigerator uses to keep food cold, but on a much larger scale. Freeze drying generally takes place in two steps: freezing and primary drying.
During freezing, water inside the food turns into ice crystals. freezer temperatures can range from -60°C/-76°F (the temperature of dry ice) to -40°C/-40°F. The lower the temperature, the smaller the ice crystals and the better the quality of the freeze-dried product.
Primary drying begins when heat and vacuum are applied to remove most of the remaining ice crystals. Freeze-dried foods are dried at or below room temperature to prevent damage from heat, so it can take several hours or even days for primary drying to be completed.
Once primary drying is finished, a secondary drying step may be used to remove any remaining traces of water. Secondary drying typically happens at around 50°C/122°F and can take several hours.
How does it work?
Freeze drying is a process where water is removed from a product by turning it into a gas, without it first turning into a liquid.
It’s done by lowering the temperature of the product so that the water inside it turns into ice, then increasing the pressure and temperature so that the ice turns directly into steam, without ever becoming water. The steam is then removed, leaving behind a dry product.
The benefits of freeze drying
Many people are interested in freeze drying because it is a way to preserve food without using chemicals, and it is a way to store food for a long time. Freeze drying also retains the nutritional value of the food.
How to freeze dry seeds
There are a few methods that can be used to freeze dry seeds, but the most common is to use a dehydrator or an oven set to a very low temperature. Freeze drying removes all the water from the seeds, leaving them in a state that can be stored for long periods of time without deteriorating.
To freeze dry your own seeds, start by spreading them out on a dehydrator tray or an oven-safe tray lined with parchment paper. Make sure the seeds are in a single layer and not touching each other. Place the tray in the dehydrator or oven and set the temperature to between 104-122 degrees Fahrenheit. Leave the seeds in the dehydrator or oven for 24-48 hours, or until they are completely dried out.
Once the seeds are completely dried, remove them from the dehydrator or oven and store them in an airtight container in a cool, dark place. They will keep for several years if stored properly. When you’re ready to use them, simply rehydrate them by soaking in water overnight before planting.
The best seeds for freeze drying
There are a number of factors to consider when choosing which seeds to freeze dry. The first is whether or not the seed is viable; that is, whether or not it will still be able to germinate and grow once it has been dried. Many seeds, such as those from annual plants, will not survive the freeze drying process. Other seeds, such as those from more hardy perennials, will be just fine.
Additionally, you’ll want to consider the size of the seed. Small seeds are much easier to freeze dry than large ones. This is because it is easier for the moisture to escape from small seeds during the drying process.
Finally, you’ll want to think about what you plan to do with the freeze dried seeds once they are dried. If you simply want to store them for long-term emergency use, then any type of seed will do. However, if you plan to plant them and grow them, then you’ll want to choose seeds that are known to be easy to germinate and grow.
Some of the best seeds for freeze drying include:
-Tomatoes
-Peppers
-Squash
-Beans
-Corn