Impact of different drying methods on the drying time, energy, and quality of green peas

The effect of seven drying methods (freeze (FD), hot air (HA), infrared (IR), microwave (MW), hot air-infrared (HA-IR), hot air-microwave (HA-MW), and sun drying (SD) methods on the drying time, the physical, qualitative and antioxidant properties, and the extraction of phenolic and flavonoid compounds in green peas was studied. Six mathematical models were also utilized to predict the moisture content of dried green peas. The results showed that the shortest and longest drying times were obtained by the HA-MW and FD methods, respectively. For all drying methods, the Page model had the best ability in predicting the drying curve. The lowest amount of specific energy consumption was achieved by the MW method. The highest color changes and the lowest amount of shrinkage occurred in the FD method. The lowest rehydration ratio was 1.23 in the SD method. The highest pH value of 6.08 was also obtained in the SD method. The amount of antioxidant capacity changes and the total phenol and flavonoid contents varied between 42.47%-88.28%, 4.52-14.59 mg GAE/gDW, and 244.62-322.44 mg QE/gDW for different methods. The FD method was found to be the best way to preserve the product properties. It was further suggested that the HA-MW method can be a promising technology for drying the green peas due to the relatively lower energy consumption, shorter drying time, and higher quality. Novelty impact statement Seven drying methods are compared for the drying of green peas. It is found that freeze drying is the best in terms of the preservation of the product quality but it is also the most expensive drying method. High-quality dried green peas can also be obtained using the combined hot air-microwave drying method, with relatively lower energy consumption and shorter drying time.