But do you have any experience with freeze-drying? Freeze drying technology protects not only the form of the food, but also the majority of the nutrients in the ingredients, making it an excellent drying method in the food sector.
The technology of freeze-drying was developed in the early twentieth century. Freeze-drying technology began to be used in food, medical, aerospace, and other industries after World War II, and it was gradually promoted industrially. Freeze-dried food, also known as FD food, has the advantage of preserving freshness and nutritional content while also being able to be stored at room temperature for more than 5 years without the use of preservatives. Organic freeze-dried food is also beginning to enter people's daily life as a casual and convenient health meal because most of the water has been removed from the completed product, making it light in weight and easy to carry and transport.
Freeze dried food has advanced to an industrial and automated level in wealthy countries such as Japan, the United States, and Europe. Freeze-dried foods of good nutritional quality account for more than half of the simple and convenient convenience food consumption pattern in these countries, and they have grown in popularity in everyday life. According to some estimates, the freeze dried food market in the United States and Japan is rather mature, with 6 million tonnes and 2 million tonnes of freeze dried food required yearly, respectively.
Organic freeze-dried foods, such as freeze-dried fruit slices, freeze-dried veggies, freeze-dried beef, and soup items, are still very standard. Unlike traditional baked, fried, puffed, and honeyed foods, freeze-dried foods retain the natural taste of the food, the color, aroma, taste, and shape of the ingredients, do not contain any additives, are well rehydrated, can be eaten ready to eat or soaked, save time and effort, are light and easy to carry, and are appealing to a wide range of consumers.
Vacuum freeze-drying is referred to as freeze-drying technology. Freeze drying, as opposed to frying or baking, or spray drying when creating powders, is the process of dehydrating and drying frozen food products by sublimating them in a vacuum environment. In simple words, lyophilisation is a frozen product's sublimation process. When a frozen liquid begins to convert into a gaseous state, it is called sublimation. Pre-freezing, quick-freezing, and vacuum drying are the three basic stages of the freeze drying process.
The three-phase change of water, which contains three phases, namely solid, liquid, and gas, and the three phases can both convert and co-exist with each other, is the essential principle of freeze drying. The three-phase change is primarily based on the pressure and temperature of water. Food that has been freeze-dried organically Freeze-drying is the process of quickly freezing fresh food such as vegetables, meat, and fruits, then sublimating the water in the food from the solid to the gaseous state under vacuum, and then parsing and drying to remove part of the combined water, resulting in low-temperature dehydration and drying.
(1) Quick-freezing, pre-freezing
The ingredients (solutes) that make up freeze-dried food must first be pre-frozen below their crystallisation temperature. The quick-freezing approach is used because the smaller the ice crystals in the meal are, and the less mechanical damage to the cells is caused.
(2) Drying in a vacuum
The freeze-drying drying process is separated into two stages: primary drying and secondary drying, also known as sublimation drying and resolution drying.
After pre-freezing, the ice must be removed from the food by sublimation, which necessitates meticulous control of two parameters: temperature and pressure. The ice crystals sublimate to water vapour and exit from the food surface when it absorbs heat under vacuum. The rate of sublimation is determined by the difference in vapour pressure between the food product and the ice collector. Molecules will transfer from a high-pressure sample to a low-pressure sample, and because vapour pressure is temperature-dependent, the food temperature must be higher than the ice collector temperature.
After initial drying, all of the ice in the food has sublimated, but there is still some liquid in the meal, thus it must be dried twice more to entirely eliminate the extra water. The extra moisture is desorbed by the high temperature in this process, which is also known as isothermal desorption.