To improve product quality and obtain suitable processing parameters for crab apple slices (CASs) produced by continuous microwave drying (CMD), the effects of processing parameters, including slice thickness, microwave power, air velocity, and conveyor belt speed, on the evaluation indexes in terms of temperature, moisture content, color (L*, a*, b*), hardness, brittleness, and total phenolic content of CASs were investigated via the response surface method. The results indicated that microwave power has the greatest effect on the evaluation indexes applied to the CASs under CMD, followed by air velocity, slice thickness, and conveyor belt speed. To produce the desired product quality, the appropriate parameters for CMD of CASs were optimized as 1.25 mm slice thickness, 14,630 W microwave power, 0.50 m·s⁻¹ air velocity, and 0.33 m·min⁻¹ conveyor belt speed. Following that, the moisture content under CMD was found to be 13.53%, the desired color, hardness 0.79 g, brittleness 12.97 (number of peaks), and the total phenolic content 5.48 mg·g⁻¹. This research provides a theoretical framework for optimizing the processing parameters of CASs using the response surface method.

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.