Application of "microwave drying" technology in the food industry
Foods usually have a moisture content of30%~97%, the use of microwave drying or microwave-enhanced drying of food has broad application prospects.
（1) Microwave quick-acting drying of food, such as using microwave heating to dry vegetables until the moisture content is lower than20%the“dried vegetables”, is more than ten times more efficient than traditional methods. This method is not only suitable for drying vegetables, but also suitable for drying seaweed foods. When observing microwave-dried vegetables under a microscope, it can be found that their tissues are second only to those of fresh vegetables, but their drying time is shorter than that of freeze-dried products. Microwave can also be used to treat fried products^Final drying not only saves oil, but also provides light and delicious food with low oil content.
Hot air drying dough requires5 ~ 8h, to avoid crusting or cracking, microwave drying as long as1 ~ 2h, drying from initial moisture content to20%, and use hot air to remove moisture to save energy25%。Drying with microwaves can also reduce bacterial contamination, such as a combination of hot air and microwaves drying garlic, which removes moisture from80%dried to10%(wet basis), then dry with microwave until5%, the total number of bacteria dropped90%, energy saving30%。
Microwave in vacuum can process temperatures higher than40℃(Sometimes even in15℃For materials that will deteriorate or degrade at a time, the vacuum drying oven can only pass through heat conduction, usually without convective heating, and the drying time is very long. Microwave vacuum dried products include fruit juice, tea powder, enzymes, vegetables (mushrooms, garlic, soybeans, etc.), and the operating cost is between spray and freeze drying. In these systems, the material is usually a paste material, laid on a conveyor belt and passed along a specially manufactured tunnel (vacuum of:133.3 ~ 2666 Pa) passes through to form bubbles, with good rehydration performance.
（2）Microwave and hot air combined drying of tomatoes, grapes, potato chips, carrots and other vegetable products can improve the quality of the product, have good rehydration and low shrinkage.
（3) Microwave puffing and drying of foods, beans, grains, potatoes, etc., with waterαAfter drying, a certain amount of food additives is added to prepare and shape, pre-dried, and then the product is quickly dried with microwaves. After the protein-based raw materials are added to starch fortifiers, salt, condiments and bulking agents, they are mixed, stirred, formed, pre-dried, and then heated with microwaves. These heated foods produce carbon dioxide and water vapor, thus obtaining soft convenience food.
（4) Microwave cooking and processing of meat Galanz andLGMicrowave ovens all give microwave oven recipes. According to the recipes, meat, seafood, and poultry can be processed to make various delicacies, saving energy on average60%Left and right, the bones can reflect microwaves, making the inside of the meat easier to cook and not limited by the size and shape of the meat piece.
（5) Microwave and infrared waves combine to bake foods that want to be eaten with tender inside and charred outside. You can cook them with microwave first and then bake them with infrared rays, such as roasted chicken with mushrooms, roast duck, roasted pork, etc.
（6Microwave sterilization and preservation of food In the microwave field, various polymer polar groups of microorganisms produce fierce rotation and vibration, causing mutations in proteins and nucleic acids, thereby killing bacteria. Generally, molds, yeasts and general bacteria are heated to70~80℃You can kill it if you use microwaves1minThe purpose of sterilization can be achieved. For the spores of molds, such as Penicillium, the spores of fungi must be found in the68~71℃after20mincan only be killed by routine sterilization, while using microwaves in68~71℃after2minConvenient to obtain satisfactory results. If using microwaves“moon cakes”Carry out sterilization, mildew prevention and preservation, and achieve good results, and no longer need to import“preservative”。Good results have been achieved in the drying and sterilization of soybean powder, chicken essence, and red sweet potatoes.