The taste quality of ready-to-eat rice is influenced by the uniformity of temperature distribution during microwave reheating. The temperature distribution uniformity of ready-to-eat rice loaded in a rectangular lunch box is investigated under microwave reheating. The results show that with a 10–80 °C temperature increase in the ready-to-eat rice, the thermal conductivity increases, dielectric constant, and specific heat increase and then decrease, while the dielectric loss factor decreases and then slightly increases. The microwave-heating process of ready-to-eat rice exhibits a clear ‘corner effect’, and the observed ‘hot spot’ results in poor temperature uniformity in ready-to-eat rice. A metalized packaging structure design is subsequently proposed to ameliorate the temperature non-uniformity. According to comparative results of four metalized packaging forms, the spray film volume and film thickness corresponding to film volume are developed as $3.5\times {10}^{-4}$ mL/${\mathrm{m}\mathrm{m}}^2$, 0.30 mm, respectively, which levels off the difference in temperature to improve the temperature distribution uniformity of ready-to-eat rice by microwave reheating.

To reduce the usage of petroleum-based plastic products, a lignin-based film material named aminated lignin/Fe(III)/PVA was developed. The mixture of 8 g lignin, 12 mL diethylenetriamine, 200 mL NaOH solution (0.4 mol·L⁻¹), and 8 mL formaldehyde was heated at 85 °C for 4 h; after the aminated lignin was impregnated in the Fe(NO₃)₃ solution, a mixture of 3 g aminated lignin/Fe(III), 7 g PVA, and 200 mL NaOH solution (pH 8) was heated at 85 °C for 60 min; after 2 mL of glycerin was added, the mixture was spread on a glass plate to obtain the aminated lignin/Fe(III)/PVA film. This film demonstrated hydrophobicity, an UV-blocking function, and a good slow-release performance. Due to the formation of hydrogen bonds between the hydroxyl groups of lignin and PVA, the tensile strength, the elongation at break, and the fracture resistance of the film were 9.1%, 107.8%, and 21.9% higher than that of pure PVA film, respectively. The iron content of aminated lignin/Fe(III)/PVA was 1.06 wt%, which mainly existed in a trivalent form. The aminated lignin/Fe(III)/PVA film has the potential to be used as a food packaging material with anti-ultraviolet light function and can also be developed as other packaging materials, such as seedling bowls, pots for transplanting, and coating films during transport.

Microwave energy utilization undergoes two stages via absorption and conversion inside ready-to-eat rice (RER) under microwave reheating. The reasonable utilization of microwave energy inside the processed material may enhance the uniformity of the temperature distribution. To analyze the uniformity changes inside RER, the effects of microwave reflection, refraction, and absorption by a metal aluminum film were studied through the thermodynamic properties. A simulation model was developed using the co-simulation method of COMSOL Multiphysics with MATLAB programming to analyze the mechanism of material properties and electromagnetic distribution on temperature distribution uniformity, as well as the formation mechanism of the temperature distribution uniformity of microwave-reheated RER. Based on models of the designed package boxes covering the metal film, the optimal structure was developed to include a metal aluminum film with a width of 5 mm and a thickness of 0.30 mm, which was sprayed on the edges and corners of a rectangular packaging box. The packaging boxes covering the metal films may reduce the average temperature of the upper and lower layers in RER by 8.03 °C and 7.42 °C, respectively, while the temperature distribution uniformity increased by 35.71% and 72.22%. The introduction of a metalized package significantly enhances the temperature uniformity inside RER under microwave reheating.

In order to improve the final quality of germination brown rice (GBR), the changes of GBR in Gamma-aminobutyric acid (GABA) and color are investigated under microwave drying conditions. Results indicate that Microwave drying process may improve GABA in GBR due to microwave volumetric heating inducing the glutamic acid decarboxylase (GAD) activity; and the dried GBR with golden appearance under the microwave intensity of 2.75 W/g and the apparent velocity of 2.50 m/s considering the drying efficiency and quality of dried GBR. In this study, microwave drying conditions not only improve the drying efficiency of GBR, but also improve the appearance and color of GBR after drying, reduce GABA degradation and control the generation of burst rate.

Traditional drying methods often result in significant loss of flavor, color, and bioactive components in food products. One effective method of improving the nutritional value of foods and shortening the drying process is to apply heat via continuous microwave drying. Understanding continuous microwave drying of crab apples is key to boosting efficiency and energy savings. In this study, crab apple slices were dried under continuous microwave drying and thoroughly investigated in terms of dehydration characteristics and quality attributes. The effects of drying conditions, including slice thickness (1–5 mm), microwave power (11400–19000 W), air velocity (0–2 m/s), and drying time (12–16 min) on the changes in temperature, moisture content, color, texture, total phenolic content, and microstructure were analyzed. Results showed that increased microwave power and decreased slice thickness significantly reduced moisture content; increasing air velocity reduced the temperature increase, whereas prolonging drying time decreased moisture content and increased drying temperature. As the slice thickness increased, the color values showed a decreasing trend while texture and total phenolic content increased. The application of higher microwave power resulted in changes in the overall color and texture, which decreased while the total phenolic content increased, additionally damaging the surface structure. Higher air velocity increased the color and texture while reducing the total phenolic content. Moreover, heightened air velocity may lead to more apparent structural changes. As the drying time increased, the color and hardness values decreased while the total phenolic content increased; prolonged drying times can significantly change the microstructure. To ensure the quality of the dried product, it is recommended that high microwave power, excessive air velocity, and extended drying times be avoided. Therefore, the appropriate conditions for continuous microwave drying of crab apple slices are a slice thickness of 1.5 mm, microwave power of 15200 W, air velocity of 0.5 m/s, and drying time of 13 min. This study may offer guidance for understanding and improving the continuous microwave drying of dried products, such as crab apples.

Reintroducing crop straw into soil boosts organic matter, but natural crop straw usually shows low nutrient content. To enhance the water absorption rate of a certain thin sheet-shaped iron-containing material, a technical approach combining ball milling, the Mannich reaction, Schiff’s base cross-linking, emulsion separation, and solid–liquid adsorption was attempted to prepare iron-containing microspheres using sodium alginate and rice straw as raw materials. This approach increased the content of the trace nutrient iron and improved the water absorption rate. The results indicated that the iron-containing microspheres exhibit a diameter ranging from approximately 15 μm, an iron content of 10.44%, and a water absorption rate of 501.76%. The release rates of iron and nitrogen in soil and water within the first day were all below 15%, while the release rates after 30 days in soil were 61.8% for iron and 44.32% for nitrogen, and the corresponding rates in water were 73.1% for iron and 63.88% for nitrogen. The water absorption capacity of the iron-containing microspheres showed a trend associated with particle size and pore structure parameters. The development of iron-containing microspheres has expanded the preparation technology for semi-interpenetrating structure type sustained-release materials, and holds the potential for further development into slow-release fertilizers.