Effect of vacuum and ethanol pretreatment on infrared-hot air drying of scallion (Allium fistulosum).


School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, People's Republic of China; School of Biological and Food Engineering, Chuzhou University, Chuzhou, 239000, People's Republic of China. Electronic address: [Email]


This study examined the effects of vacuum, ethanol pretreatment, and infrared-hot air drying methods on the characteristics and quality of scallion slices. The pretreatment of scallion includes four conditions: 1) Control: soaking in distilled water under normal pressure, 2) Ethanol: soaking in 75% ethanol under normal pressure, 3) Water + VC: soaking in distilled water under a vacuum of 0.6 bar, 4) Ethanol + VC: soaking in 75% ethanol under a vacuum of 0.6 bar. The pretreatment times were 5, 10, 20 and 30 min. The drying process was done in an infrared hot air drying oven at 60 °C. The ethanol pretreated samples exhibited better rehydration, odor, vitamin C retention, bactericidal effect and significantly reduced drying time. Water + VC samples showed better scallion morphology and color. Ethanol + VC samples showed the combined advantages of ethanol and Water + VC pretreatments. Therefore, Ethanol + VC pretreatment can significantly improve the drying rate and quality of scallion.


Ethanol,Infrared-hot air drying,Pretreatment,Scallion,Vacuum,

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