Microwave baking holds broad prospects

Using microwave technology to process food is an advanced method that has become fashionable, convenient, fast, and highly hygienic in recent years. Especially in the processing of baked goods, microwave technology can precisely control the "cooking time" at each processing step, thereby significantly improving the yield of baked products. Compared to traditional techniques, it has unparalleled advantages, making the application of microwave technology in baked goods have a very broad prospect. Currently, microwave baked products available on the market include microwave cakes, microwave bread, microwave doughnuts, and microwave biscuits.

However, processing baked goods using microwave technology is not entirely satisfactory. Given that microwave technology is still in its exploratory and developmental phase, coupled with the vastly different reactions of various factors during the baking process, it is inevitable that some deficiencies may arise in the products. Based on the current understanding, these deficiencies in baked goods mainly manifest as insufficient expansion, overly hard texture, poor softness, and a lack of the desired browning and Maillard characteristics typical of baked goods.

According to experts, the main reason for the aforementioned deficiencies lies in the fact that the physical and chemical changes that occur in the main components of baked goods during prolonged heating in traditional heating systems, as well as the interactions between various components, are not fully exhibited in the short time frame of microwave technology processing. Furthermore, the different heating mechanisms between microwave technology and traditional methods, coupled with the unique interactions between various components during microwave energy application, all contribute to the aforementioned deficiencies.

Firstly, the difference in heating methods between microwave baking and traditional baking is explained through a comparison between the two. He points out that the traditional heat transfer methods are convection and conduction, relying on medium convection and radiation from the oven wall to transfer heat to the surface and then to the center of the object. That is, as the temperature rises, water vapor moves to form heat conduction between the container and the object. Microwave heating, on the other hand, generates heat through the interaction between microwaves and charged ions or polar molecules, and conduction occurs only after heat is generated. In other words, both the environment inside the microwave oven and the interior of the object are heated and undergo mass transfer simultaneously.

According to the technical staff, traditional baking generally involves four stages: 1. Formation of a white hard shell; 2. Heat transfer from the hard shell to the interior; 3. Gelatinization or cooking process; 4. Browning. In traditional baking, the large amount of air inside the dough hinders heat transfer, making heating difficult and slow. Microwave heating, on the other hand, uses microwave penetration to transfer heat inside the baked product, eliminating the four stages mentioned above and the problem of air obstruction. This allows the temperature of microwave-baked products to rise rapidly to the cooking stage of traditional baking. The technical staff believes that because microwave baking eliminates the four stages mentioned above, the surface temperature of microwave products cannot reach the requirements for sugar caramelization and Maillard browning reactions, so microwave products almost never undergo browning and cannot form a hard shell at all.

In various baked products, starch serves as the basic raw material, and its distinct reactions to microwave baking and traditional baking can yield different outcomes. Technicians from Shandong Kehong Microwave Energy Co., Ltd. discovered through testing the changes in the microstructural characteristics of starch gelation during microwave and traditional heating that the structure of wheat starch heated by traditional methods is more uniform than that heated by microwaves. Therefore, they proposed using a combination of microwave and forced convection heating to promote browning in microwave-baked products, thereby forming their typical surface and flavor.

It is understood that the aforementioned method proposed by Kehong is inspired by an international concept that enables browning of microwave-baked products. This concept is referred to within the industry as an impact system that integrates heating and microwaves. The term "impact" is used to describe the process of directly spraying high-temperature fluid onto the surface of baked products to accelerate their heating. Technical personnel from Shandong Kehong explained that the rapid impact baking of the product surface aligns perfectly with the rapid microwave baking of its interior, ensuring that the product achieves perfect results in both its surface characteristics and internal structure. Additionally, the hard shell formed by impact baking can reduce the high moisture loss rate caused by evaporation during microwave baking. Therefore, once this concept is realized, it has the potential to become an effective measure for achieving successful browning of baked goods.

According to the technical staff of Kehong Microwave Energy, using microwave energy to process tea has long become a conventional technology in developed countries such as Japan. However, in China, which is slightly inferior in this technology, it was still a difficult problem at that time. Shandong Kehong Microwave Energy Co., Ltd. leveraged its technological and equipment advantages, drew on successful foreign experiences, and solved this problem in just one month, successfully exporting the technology and meeting the requirements of foreign businesses. The relevant department head in Shandong commented that this move not only improved the quality and grade of tea but also created significant economic benefits.

To address the challenge of aroma formation in microwave-baked foods, two approaches have been explored: firstly, replacing modified starch with low-amylose starch to reduce potential binding sites; secondly, incorporating specific spices designed and produced specifically for microwave baking products. These measures effectively overcome this shortcoming. According to technical personnel from Kehong Microwave Energy, during microwave baking, individual aroma components are prone to loss due to distillation, starch and protein adsorption, and chemical decomposition. The spices used in microwave food not only need to have the aroma of fruits and lipids such as lemon and butter, but also the typical baking aroma produced by the Maillard reaction and sugar caramelization.