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Optimum technology and quality evaluation of short- and medium-wave infrared radiation (SMIR) dried carrot slices were studied. Effects of drying temperature, drying time and infrared power of SMIR drying on the moisture content, color parameter and β-carotene content of dehydrated carrot slices were investigated. The experimental data were well predicted by a modified second-order polynomial model. Drying temperature and drying time had significant effects on moisture content, color parameter and β-carotene content. However, infrared power only showed significant effect on the moisture content. Response surface method (RSM) was used for optimization of SMIR drying of carrot slices, and the optimum condition was found as drying time of 50 min, infrared power of 1125 W, and drying temperature of 70 °C. SMIR dried products were proved to be favorable by comparing with hot-air dried ones due to its higher rehydration ratio (6.89) and β-carotene content (462.48 μg/g).

The effects of instant controlled pressure drop (DIC) drying, and blanching-assisted DIC (B + DIC) on texture, volume ratio (VR), colour, microstructures of different tissues, and cell-morphology of fruit and vegetable chips was examined. Results revealed that B + DIC had a significant effect on fruits and vegetable chips as compared with DIC treated. The DIC dried mango chips were observed to have low hardness (26.12 N) and maximum crispness (10.43) that were also observed in mango chips under B + DIC treated (14.66), exhibiting a puffy structure and crispy texture. Well expanded structure which reflected by VR was found in the mango (0.46 mL) and king oyster mushroom (KOM) (0.36 mL) chips under both treatments. The maximum total colour changes (∆E) were also obtained in the mango (30.40) and carrot (42.87) chips under B + DIC. The microstructures of the apple, carrot, KOM and potato chips products, which corresponded to its well expanded appearances, showed a honeycomb-like pores structure, observed for DIC treated apple, fresh potato, B + DIC dried KOM as well as in sweet potato. In addition, the B + DIC-treated carrot chips, pores size, increased the cell wall and expanded. Moreover, the mushroom chips mostly were shrunken after hot water blanching.

In this paper, short- and medium-wave infrared radiation (SMIR) drying characteristics of kiwifruit slices with/without osmotic dehydration (OD) were investigated. High fructose corn syrup (HFCS) was selected as the best osmotic solution and coupled with SMIR. Both infrared drying processes with/without OD occurred mainly in the falling rate period. Results indicated that the Logarithmic model and Page model were best in predicting moisture transfer for the kiwifruit slices with and without OD, respectively. The values of effective diffusivity ranged from 4.10×10‒10 m2/s to 9.52×10‒9 m2/s and from 3.10×10‒10 m2/s to 1.16×10‒8 m2/s for kiwifruit slices with and without OD, respectively. During the overall falling rate period, the activation energy value was 29.51 kJ/mol and 27.44 kJ/mol for the osmosed and non-osmosed kiwifruit slices, respectively. As compared with non-OD, OD pre-treatment could improve the drying characteristics, decrease color change and increase the retention ratios of ascorbic acid and chlorophyll.

The effect of osmotic dehydration (OD) and ultrasound-assisted osmotic dehydration (ULOD) on drying kinetics and quality of peach cylinders by infrared radiation drying were investigated. The moisture state and redistribution after osmotic pretreatments and subsequent drying process were also studied by low field nuclear magnetic resonance. The water loss and solute gain increased with osmotic time, and ULOD could promote water transfer. The signal amplitude of free water and immobile water diminished and shifted to the left for samples pretreated by both ULOD and OD. The brightness in T2-weighted images appeared a declining trend with increasing osmotic time of ULOD and OD, indicating the moisture content reduced gradually. During dying process, the free water of all samples was removed completely after drying for 120 min. ULOD and OD could increase water activity and decrease shrinkage of samples. Long pretreatment of ULOD and OD improved the color of dried peach cylinders.

Effects of two combination drying methods as well as two single drying methods on the quality of papaya chips were studied. The longest drying time was found in freeze drying (FD), while the shortest drying time was found in hot-air-explosion puffing drying (HA-EPD). The papaya chips dried by FD exhibited the lowest shrinkage, while the highest shrinkage was found in the hot-air drying (HAD) dried sample. The lowest and highest total color differences (△E) were found in the FD and FD-EPD. The FD dehydrated papaya chips showed the highest retention of ascorbic acid and total carotenoids. The fastest rehydration rate was also observed in samples dried by FD. The worst rehydration capacity was found in FD-EPD, which related to the collapsed porous microstructure. Papaya chips prepared by FD-EPD showed crispier texture, which were in line with their expanded porous microstructures. In conclusion, the application of combining with EPD may improve the retention of nutrition of papaya.