Effect of different drying techniques on moisture migration, nutritional profile and sensory attributes of peanut pods

Abstract

This study investigated the impact of various drying technologies on peanut pods, specifically heat pump drying (HPD), infrared drying (ID), and their combination (HPD–ID). These methods were analyzed for their effects on drying kinetics, water migration, physical and chemical properties. of Fat and protein concentration, and the changes in tissue structure of peanut pods under different drying technologies were studied experimentally. The drying times for HPD, ID, and HPD–ID were 14, 15, and 12 h, respectively. Analyzing the water content using low-field nuclear magnetic resonance showed that the primary water loss during drying was from free and weakly bound water. Compared with those in fresh samples, the contents of saturated fatty acids remained primarily stable under HPD at 15.20 g/100g, with those of unsaturated fatty acids remaining 84.81 g/100g. ID showed a higher content of polyunsaturated fatty acids at 5.68 g/100g. All drying methods led to an increase in the acid value (P < 0.05). Compared with other samples, HPD samples exhibited the highest peroxide value at 0.07 g/100g, which was significantly larger compared to those of ID and HPD samples (P < 0.05). Compared with those for other samples, the amino acid content and composition of ID demonstrated the smallest change. The color difference in ID (10.24) was greater than those in HPD (5.71) and HPD–ID (6.11) (P < 0.05). During drying, the hardness of both peanut kernel and shell generally showed an upward trend; meanwhile, peanut pods experienced pore and tissue damage, particularly under HPD, which resulted in the most significant structural damage. Overall, HPD–ID proved to be highly effective for peanut pods. This method resulted in a low drying time, helped preserve tissue structure, and retained nutritional quality of the peanut pods. The applications of HPD, ID, and HPD–ID provide a strong theoretical foundation for advancing new industrial drying technologies for peanut pods.