As the world food industry is increasingly strict with hygiene standards, green food processing technology is increasingly favored. Microwave technology is an advanced application technology in food processing engineering in recent years Microwave drying 、 Microwave sterilization , microwave puffing Microwave thawing , microwave baking microwave heating The application of extraction technology in food industry was analyzed and explained in detail.
1. Microwave drying
Microwave technology can be used independently or combined with traditional heating method in drying process. It is most effective for food with water content below 20%, and has been successfully applied to drying potato chips, noodles, condiments, snacks, seafood, vegetables, fruit powder, egg yolk powder, ginseng, honeysuckle, dried meat, preserved meat, mushrooms, tea and other varieties. Compared with traditional drying equipment In contrast, it not only has high drying efficiency and short drying time, but also can better maintain the color, fragrance, taste and nutrient content of materials. At the same time, it has unique sterilization advantages, which is conducive to product storage.
2. Microwave sterilization and preservation
The traditional sterilization equipment for food can usually be realized by conventional technologies such as high temperature drying, blanching, pasteurization, freezing and preservatives. However, most of these equipment are huge, with long processing time, incomplete sterilization or difficulty in automatic production, and often affect the original flavor and nutrition of food. The microwave sterilization is to make the microorganisms in food subject to the combined effect of microwave thermal effect and non thermal effect, so that the protein and physiological activity substances in their bodies will change, causing the growth and development of microorganisms to delay and die, so as to achieve the purpose of food sterilization and preservation. The microwave sterilization temperature is 70 ℃~90 ℃, and the time is about 90 s~120 s. Microwave sterilization is widely used in various foods due to its short time and low temperature. For example, plastic bags are used to package chicken, duck, chicken feet, barbecue, meat floss, smoked fish, beef jerky, etc. for sterilization and preservation. After microwave sterilization, it is fresh and soft, and still retains the original flavor of the product.
3. Microwave puffing
Now the puffer produces small food by extrusion, frying and airflow. In recent years, many researchers have studied the puffing technology of rice noodles, potatoes, sweet potatoes and some fruits by microwave. Taking the microwave puffer for glutinous rice as an example, the main power of material puffing is the water contained in the material. When the rice germ is heated rapidly after being exposed to microwave radiation, the water between the material fiber structures will be vaporized into steam in a short time, resulting in a strong vapor pressure difference and promoting the expansion of the fiber structure spacing. The water will escape and the material will be shaped into micropores to obtain puffed products.
4. Microwave thawing
Thawing is the process of raising the temperature of frozen solid food below freezing point. Microwave thawing does not need to open the product package, and can be completed in a few minutes, while it takes 2-5 days to thaw in the traditional bubble pool, thus reducing the breeding and corruption of food microorganisms. Microwave thawing can save processing time, reduce juice loss, have little or no mass loss, take up less space (about 1/10 of the traditional technology), reduce production complexity, avoid bacterial growth, maintain the acidity of meat, and reduce labor. Microwave technology can be applied to thaw frozen steamed bread, frozen meat and their products; Microwave heating can remove garlic odor with good effect on the premise of retaining garlic color, flavor, texture and nutrition.
5. Microwave baking
Under the direct action of microwave electromagnetic field, food products reach high temperature instantly without heat conduction. Microwave heating is uniform, sanitary, efficient, and has good puffing effect. Compared with traditional ovens and baking equipment, microwave There is no thermal inertia, and the production environment is good. The processed products are crisp and refreshing, with rich flavor, high expansion rate, natural color, and less loss of nutrients. Microwave baking equipment can not only achieve fast baking, but also be used for drying dried fruits and nuts, drying, sterilization, ripening, automatic opening, puffing, crispness and other processing.
6. Microwave extraction
The mechanism of microwave extraction can be considered from two aspects. On the one hand, the microwave radiation process is that high-frequency electromagnetic waves penetrate the extraction medium and reach the vascular bundle and glandular system inside the material. Due to the absorption of microwave energy, the internal temperature of cells rises rapidly, which makes the internal pressure of cells exceed the capacity of cell wall expansion. The cells break, and the effective ingredients in cells flow out freely, which are captured and dissolved by the extraction medium at a lower temperature. The extracted material is obtained through further filtration and separation. On the other hand, the electromagnetic field generated by microwave accelerates the diffusion rate of the extracted components to the extraction solvent interface. For example, when water is used as the solvent, under the microwave field, the water molecule rotates at a high speed to become an excited state, which is a high energy unstable state, or the water molecule vaporizes, strengthening the driving force of the diffusion of the extracted components; Or the energy released by the water molecule itself to return to the ground state will be transferred to other material molecules, accelerating its thermal movement, shortening the time for the extraction component molecules to diffuse from the inside of the material to the extraction solvent interface, thus improving the extraction rate.