Two‐step drying based on air jet impingement and microwave vacuum for apple slices
2019
Yin, Xu | Jiao, Shunshan | Sun, Zhongqi | Qiu, Gan | Tu, Kang | Peng, Jing | Pan, Leiqing
In this study, a novel two‐step drying method using a combination of air jet impingement (AJID) and microwave vacuum drying (MVD) was proposed for drying apple slices. Chemical (vitamin C, total phenolic, soluble solid content, and titratable acid) and physical properties (energy consumption, color, and rehydration ratio) were assessed and compared with those of apples dried solely by hot air drying, freeze‐drying, AJID, and MVD, respectively. Results showed that the optimal conditions for drying apple slices using air jet impingement were 65°C drying temperature, 2.3 m/s air velocity, and 6 mm thickness; the optimal combination was used first for 60 min AJID, followed by 40 min MVD, with final moisture content of 12.65 ± 0.63%. Based on the quality of apple slices and the energy consumption of the drying equipment, combined AJID‐MVD appears to be a promising method for drying apple slices. PRACTICAL APPLICATIONS: In practical production, the enterprise usually buys semidried apple slices for producing apple chips. This study aimed to study the effect of different drying methods such as hot air drying, freeze‐drying, air jet impingement drying, and microwave vacuum drying on the quality of apple slices, and optimize the drying parameters. The results presented can be used for guiding semidry apple slice production using suitable drying methods based on the quality of the apple slices and energy consumption.
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