Compared with convection drying, infrared radiation drying could cut energy consumption by 50%. Medium- and short-wave infrared radiation drying (MSIRD) is a novel dehydration technology with high efficiency. PVD has been successfully applied to materials containing heat-sensitive components, such as mango, Ginkgo biloba L. The samples are kept in a vacuum condition for quite a while during the process, which can reduce the occurrence of oxidative browning of the nutrients in the material. Pulsed vacuum drying (PVD), is a relatively novel dehydration technology that uses sequential change in vacuum pressure in the dryer interior to enhance moisture translocation and quality of materials during the dehydration process. In view of these advantages, TH-HAD has been primarily employed in the drying of long-grain rice, longan, shiitake mushroom, etc. It can reduce the shrinkage of material by increasing the RH of the medium, prevent the surface of the material from deteriorating and alleviate the oxidation reaction of heat-sensitive materials during the drying process. Hot air drying based on temperature and humidity control (TH-HAD) is a new technology for drying agricultural materials by regulating the values of temperature (T, ☌) and relative humidity (RH, %) of the drying medium during the moisture removal process. The technology has been effectively applied to mushroom slices, potato cubes, red cabbage, etc. Its convective heat transfer coefficient is considerably higher than that of HAD, with high efficiency and low energy consumption. The findings in current work implied that PVD could be a promising drying technique for garlic slices.Īir impingement drying (AID) technology uses a nozzle to generate high-speed hot air to directly impact the surface of materials for energy exchange. The MSIRD process produced the densest structure, and caused an additional loss of color and phytochemical contents. VFD maintained a complete garlic slice structure with the minimum shrinkage and the best appearance. The allicin and soluble pectin contents of garlic slices treated with PVD were higher by 8.0–252.3% and 49.5–92.2%, respectively, compared to those of the samples dried by other techniques. In response to thermal effects and pressure pulsations, the cell walls gradually degraded, and the cell and organelle membranes ruptured. Samples dried with PVD showed the smallest color difference (Δ E*), better rehydration capacity and desirable reducing sugar content. Based on the experimental results, the Weibull model fitted the experimental results better ( R 2 > 0.99) than the Wang and Singh model. Effects of vacuum freeze drying (VFD), air impingement drying (AID), hot air drying based on temperature and humidity control (TH-HAD), pulsed vacuum drying (PVD), and medium- and short-wave infrared radiation drying (MSIRD) on the drying characteristics and physicochemical properties of garlic slices were investigated in the current work.
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