Impact of apple slice thickness and water-soaking pretreatment on catalytic infrared blanching efficiency and subsequent hot air drying performance

This study examines the effects of water soaking pretreatment prior to catalytic infrared (CIR) blanching and hot air drying (HAD) on the drying characteristics, physicochemical properties, and quality attributes of dried apple slices. Apple slices were soaked in water before undergoing CIR blanching and HAD. The results indicated that water soaking significantly enhanced the efficiency of CIR blanching, resulting in faster polyphenol oxidase (PPO) inactivation, greater moisture loss, and better surface color retention compared to untreated samples. Microstructural analysis showed that the pretreatment caused more pronounced cellular disruption in the apple tissue, facilitating moisture removal during the drying process. The combined treatment of water soaking, CIR blanching, and HAD (CIR-HAD) substantially improved drying kinetics, reducing the drying time by 64 to 74% compared to HAD alone. Furthermore, CIR-HAD samples exhibited higher porosity, lower apparent density, and improved rehydration capacity. Thermal analysis revealed that CIR blanching promoted starch gelatinization at lower temperatures and enhanced starch retrogradation during rehydration, which contributed to improved textural properties in the rehydrated samples. Sensory evaluation indicated that CIR-HAD samples dried at 80 °C received the highest overall acceptability scores. These findings suggest that the integration of water soaking pretreatment, CIR blanching, and HAD represents a promising approach to enhance drying efficiency and improve the quality attributes of dried apple slices.