Impacts of non-thermal pretreatments on banana slices during microwave vacuum dehydration using THz-TDS and NIR-HSI techniques

Microwave vacuum dehydration (MVD) has gained widespread acceptance as a superior alternative to traditional methods like hot air drying due to its rapid dehydration capabilities and enhanced quality retention. However, improving drying efficiency and achieving effective real-time monitoring during the MVD process continues to pose significant challenges. This study investigated the effects of various non-thermal pretreatments, including L-ascorbic acid, osmotic dehydration, and ultrasound-assisted osmotic dehydration, on the drying kinetics and colour preservation of banana slices during MVD. Utilising advanced non-invasive techniques such as near-infrared hyperspectral imaging (NIR-HSI) and terahertz time-domain spectroscopy (THz-TDS), the research revealed that both osmotic dehydration and ultrasound-assisted osmotic dehydration pretreatments significantly expedited dehydration. Furthermore, ultrasound-assisted osmotic dehydration proved particularly effective in maintaining the desired colour, exhibiting minimal changes in the brown index (BI). Despite the differing scanning mechanisms of NIR-HSI and THz-TDS, both methods exhibited strong potential for real-time monitoring of the MVD process, achieving moisture content loss prediction accuracies with R² values of 0.9828 and 0.9124, respectively. By minimising environmental moisture interference and optimising algorithms, these innovative sensing methods could be widely implemented for real-time monitoring of the dehydration process.