Effects of radiation temperature on dehydration and moisture migration in banana slices during far‐infrared radiation drying

Abstract

The changes in the various water states of bananas dried at different far-infrared radiation (FIR) temperatures were investigated via low-field nuclear magnetic resonance (LF-NMR). Results revealed that increasing FIR temperatures could significantly enhance drying rates. Scanning electron microscopy results demonstrated that FIR heating could produce additional porous structures in dried bananas and that porosity increased with the elevation of FIR temperatures. LF-NMR results revealed that high FIR temperatures were associated with significant changes in the peak areas of different water states, indicating that increasing FIR temperature was beneficial to hastening water migration. Free water was removed first during drying. At the end of drying, residual moisture in banana samples was dominated by bound water. The images of moisture distribution in banana slices at various FIR temperatures revealed the regulatory mechanism of moisture transfer. Water was gradually lost from the outside to the inside of samples, and high FIR temperatures accelerated dehydration rates. Practical applications Far-infrared radiation (FIR) drying is a high-efficiency modern drying technology with the advantages of high dehydration speed and uniform heating. This study confirmed that FIR drying could significantly reduce dehydration duration compared with traditional hot-air drying. The increase in FIR temperature could expand mass transfer microtunnels, accelerate water migration, and shorten drying time. Therefore, FIR drying is an effective and prospective method for the rapid dehydration of banana slices and other agricultural products.