1 FD technology principle In nature, water has three physical forms: solid phase, liquid phase and gas phase. When the pressure drops to 646.6 Pa and the temperature falls below 0°C, water sublimates from solid ice directly into water vapor without passing through the liquid phase. FD food uses the principle of sublimation to place the moisture-containing materials in a vacuum tank after pre-freezing, and heat them through heat medium radiation to dehydrate and dry the materials. FD technology dehydrates and dries materials through sublimation without destroying the original physical and chemical structure of the material, which can preserve some heat-sensitive and volatile components to a large extent. Therefore, FD technology-processed materials The preservation rate of the intrinsic nutrients of food can reach more than 96%, and the very light aromatic oil contained in the food will also be retained on the surface of the food without loss. Compared with food that has been dehydrated through heat treatment, the biggest advantage of FD products is that it can keep the original shape, color, and nutritional content of the food basically unchanged. Sometimes it even enhances the taste and aroma of some products, improving the quality of the food. The flavor increases the palatability of food, and FD products can be stored for a long time without refrigeration. 2 The production process of FD products The following takes the production process of FD garlic powder as an example to briefly describe the general production process of FD products. Garlic is a plant of the Allium genus in the Liliaceae family. It is widely distributed around the world and is also commonly grown in my country. Garlic is one of the spicy vegetables loved by Chinese people and has high nutritional value. Among them, the Ge and Se contained in it are human body’s anti-oxidants. An indispensable element of tumors. A glycoside in garlic can effectively eliminate fat deposited on blood vessels, and has the effects of lowering blood lipids and resisting vascular sclerosis. Allicin, the main functional ingredient in garlic, is a broad-spectrum antibiotic that has a strong killing effect on a variety of bacteria and fungi. However, allicin is extremely unstable and is easily destroyed when exposed to heat and ineffective when exposed to alkali. . At 0-50°C, the higher the temperature, the faster the content of allicin decreases; below 0°C, the content of allicin decreases gently, and the pH value is 3.0-5.0, which is the most stable. Considering the properties of garlic, in order to retain the active ingredients in garlic to a greater extent, freeze-drying, that is, FD technology, is a more effective method. 2.1 Process: Garlic is washed in cold water, soaked in cold water, rubbed to remove the skin, cut into slices, soaked in acid, drained, plated, pre-frozen, vacuum dried, discharged, coarsely crushed, and packaged. 2.2 Process Parameters: The thickness of garlic slices is 1.5-2.0 mm, and the plate thickness is about 1 cm. The pre-freezing temperature should be 5-8°C lower than the crystallization point. Post-processing should be performed below 25°C to prevent garlic powder from absorbing moisture and expanding. It becomes sticky and affects product quality. 2.3 Freeze-drying process The freeze-drying process is usually divided into two drying stages: sublimation drying and analytical drying. Due to the large amount of water in the sublimation stage, the maximum heating power is generally used. When the temperature of the upper part of the material reaches the temperature of the heating plate, this stage ends. In the analytical drying stage, due to the end of sublimation and the degree of vacuum, the heating power should be controlled, that is, the temperature of the heating plate should be lowered to ensure that the temperature of the dry food is lower than the maximum allowable temperature. The end point of this stage is when the material reaches the set value, which is reasonable. Setting the time for sublimation and analytical drying is an important aspect to ensure product quality and energy saving. The optimal freeze-drying process of garlic powder is as follows: Pre-freeze to -35°C, wait for the heating plate to heat up to 60°C, keep it for 8.5 hours, then cool it down to 40°C, keep it for 4-5 hours, and maintain the highest vacuum throughout the process. Tests have shown that foods such as garlic, which are easily destroyed by heat treatment and have nutrients, are most suitable for processing with FD technology. 3 Application of FD technology in my country's food industry 3.1 Types of FD products in my country 3.1.1 Vegetables Coriander, cabbage, chives, shallots, spinach, subs, yams, broccoli, carrots, sweet potatoes, etc. 3.1.2 Condiments Various vegetable and egg soup cubes, various seafood soup cubes, jams, soups, etc. 3.1.3 Fruits Bananas, strawberries, pineapples, apples, lychees, longans, pears, etc. 3.1.4 Meat: Barbecued pork, beef, mutton, shrimp, turtle, squid, etc. 3.1.5 Food categories: Instant noodles, instant porridge, instant Lanzhou ramen, instant mutton steamed buns, instant wontons, military food, pet food, etc. 3.1.6 Microparticles Garlic powder capsules, baby milk powder, ice cream powder, various fruit powders, etc. 3.1.7 Fungi: Tricholoma matsutake, mushrooms, white fungus, fragrant rhubarb, etc. 3.2 FD technology can also be used for the preservation of various bacterial species. For example, Lactobacillus acidophilus has health-care effects, and there have been more and more studies in this area in recent years. Live bacteria preparations should maintain a high level of viable bacteria before consumption, and many current products cannot effectively prevent the attenuation of the number of viable bacteria. How to increase the amount of viable bacteria and extend the storage period of live bacteria has become a research and development project for live bacteria preparations. technical key. The production of viable bacterial preparations through FD technology is an ideal one among various preservation methods. 3.3 Dehydrated vegetables Dehydrated vegetables are a popular best-selling food in the world in recent years. They process fresh vegetables (moisture content 80%-95%) into dried products (moisture content 5%-8%) to achieve a high degree of freshness (preservation). It is a refined dish with 70% nutritional content and 70% color retention. It can also maintain its flavor and good palatability) and is easy to store and transport.

There are three processing methods for dehydrated vegetables: normal pressure hot air drying, vacuum drying and vacuum freeze drying. Among them, the normal pressure hot air drying method is more commonly used, but the quality of its dried products (freshness retention and rehydration properties) is far inferior to that of vacuum drying and vacuum freeze drying. Moreover, with the improvement of people's living standards, consumers are more concerned about the nutrition and convenience of food. Safety has put forward higher requirements, so FD technology has gradually been understood and recognized by people. In the future processing of dehydrated vegetables, FD technology has a tendency to gradually replace normal pressure hot air drying. 3.4 FD Soup Cube FD soup cube is also a new force in convenience food that cannot be underestimated in recent years. Among the current convenience food categories, instant noodles occupy the majority of the market share, attracting consumers from all walks of life with their convenience. However, the nutritional value of instant noodles is far inferior to its convenience, which makes many people think of its nutritional deficiencies while enjoying convenience. FD soup cubes can be used as a convenience food alone, or can be eaten together with instant noodles. FD soup cube is a convenient soup cube made from fresh soup through FD technology. When eating, you only need to add an appropriate amount of hot water to get a delicious and nutritious soup. FD soup cube contains vegetables, eggs, lean meat, vermicelli, etc. It is much more nutritious than instant noodles. It can be used as breakfast, lunch and dinner. It is nutritious and convenient, and is especially suitable for children and the elderly. Because it is light and easy to store and transport, it is more suitable for consumption when traveling. It is easy to carry, ready to eat, and has comprehensive nutrition. It is an increasingly growing category of convenience food. In recent years, FD instant noodles have also appeared on the market. It changes the frying process of traditional instant noodles in my country and uses FD technology to dehydrate and dry the noodles, which not only avoids the damage and loss of nutrition caused by frying, but also It retains the original flavor of noodles and can be said to be a green food. Instant noodles are not fried, have a relatively extended shelf life, and have good rehydration properties. They have attracted widespread attention from consumers as soon as they were launched. 3.5 FD milk Milk is a very important nutritious food in our family life. It can provide rich calcium and protein for the human body. However, considering the short shelf life of milk and difficulty in transportation, some FD manufacturers in my country have begun research on FD milk. After years of hard work, FD milk has also become a bold attempt. FD milk is made from 250 mL of liquid milk into a milk ball the size of a camphor ball. After the milk ball is brewed and reconstituted with boiling water, you can get a cup of fresh milk with a rich milky aroma. It is reported that France is the only country in the world involved in this invention, which is still in the experimental stage. 3.6 A bold attempt to dry seafood using FD technology. Sea cucumbers are low-fat, high-protein foods with extremely high nutritional value. However, ordinary drying methods limit the rehydration of sea cucumbers and cause a certain loss of nutrients. After being processed through FD technology, almost all the nutrients of sea cucumbers can be retained, and they can be absorbed by the human body to the greatest extent after consumption, achieving an effect unmatched by other methods of drying sea cucumbers. At present, the existing FD seafood products include FD sea cucumber, FD squid and FD clams. 4. The current situation and development of my country’s FD industry. The above introduction is about the representative FD products that have appeared in the Chinese market. However, nationwide, my country’s FD industry is still in the early stages of development, and the country’s FD equipment charging area is only 18 000 m2, the total annual FD food production is only 1.5×104 t. In terms of loading area, our country is only equivalent to Japan's level in the early 1980s; in terms of output, our country is only equivalent to the United States' level in the mid-1960s. This is in line with the fact that our country is rich in resources and has a large population. The current situation is extremely inconsistent, which also reflects the gap between my country's food industry and developed countries from one aspect. As my country's economy grows year by year and national living standards improve, people will no longer be satisfied with traditional dehydrated and dried food, so FD technology will have great room for development. Experts predict that by 2010, my country will only need high-end instant noodle accessories, which will require about 4×104 tl of FD food. Together with various fast food ingredients, soups, beverages, etc., the annual consumption of FD food will exceed 10×104 tlul. Moreover, 98% of my country's existing FD products are exported, and the domestic FD industry mainly relies on the international market. In recent years, the demand for FD products in major FD food consuming countries such as the United States, Japan, and Europe has been increasing. There is an endless stream of foreign businessmen coming to my country to purchase FD products. At present, the supply of FD products in the international market is still in short supply. situation. Therefore, in terms of the market, whether it is the domestic market or the international market, the FD industry has an extremely broad development space that needs to be explored urgently. It is understood that the production of 1 kg of FD strawberries can earn 7 US dollars in foreign exchange, which is equivalent to exporting 1 color TV set; the profit of producing 1 tFD of vegetables is more than 5 times higher than that of hot air drying products. It can be seen that FD products have great economic benefits and are a promising export project for earning foreign exchange. In recent years, due to the high cost of processing agricultural products in some developed countries, manufacturing industries have turned to my country. Therefore, we should seize the opportunity and actively adopt joint ventures, cooperation or self-investment to expand the production scale of FD food and promote the development of my country's FD processing industry. Rapid development.

At present, many food processing companies in my country have achieved gratifying results in the application of FD technology. Among them, Shandong Yuanyang Food Co., Ltd. is worthy of attention. Its chairman Song Shuxiao has obtained 15 invention patents in 3 years. Breakthrough progress has been made in the field of food processing. The instant wontons invented by him have overcome a problem that Japanese researchers have not solved for many years. In addition, dehydrated grapes and freeze-dried sea cucumbers have also filled gaps in the international market with FD technology. Our country has rich agricultural and animal husbandry product resources, but our country's agricultural and animal husbandry products have always been in the original product or primary processing stage, with low technical content. The FD industry is an emerging industry with high technical content and high added value, which is suitable for our country's resources. The current situation is that the country is rich, has a large population, and has low agricultural and animal husbandry product processing technology. Vigorously developing the FD industry in fruit and vegetable production bases can not only digest local agricultural product resources, but also earn considerable foreign exchange. At the same time, it solves the employment problem of my country's agricultural population, causing farmers' income to increase year by year and their living standards to improve rapidly. The production cost of FD food is relatively low. As long as suitable FD equipment is used and the optimal conditions for FD production are controlled, high-quality FD products can be produced. FD products are highly profitable and have low risks, so they are worthy of promotion and strong support. Foreign exchange-earning projects have huge development potential and room for development. In short, the FD industry has quietly emerged in our country and is being widely understood and recognized by people. With the development of science and technology and the take-off of our country's economy, it will definitely lead to the increasing progress and improvement of FD production equipment and technology. I believe that in the near future, FD food It will also appear on our daily dining table.