Nonthermal pretreatments enhances drying kinetics and quality properties of dried ginger (Zingiber officinale Roscoe) slices

The objective of this present work was to investigate the effect of ultrasound (US), osmotic dehydration (OD), and osmosonication (OS) pretreatment on microstructure, weight loss, texture, mass transfer, chromatic properties and drying kinetics of ginger slices under relative humidity convective drying. The results revealed that OS pretreatment yielded higher weight loss (16.5%) and lower firmness (12.11 N) than US (9.8%, 20.33 N) and OD (6.5%, 15.30 N). Microstructure analysis showed that OS, US, and OD pretreatments altered cell structure and resulted in the observable formation of several microchannels and collapsed the cell structure. Mass transfer data showed that the OS pretreated sample led to higher solid gain (3.2%) and water loss (5.1%) than the US (2.36%, 4.2%) and OD (1.7%, 2.53%) pretreatments. The chromatic property analysis revealed that the chroma value and hue angle was higher for OS treated sample (29.74, 88.77°) compared the US (26.95, 85.76°) and OD (22.96, 82.24°) treated sample. Among the three pretreatments, OS was found to enhance the drying kinetics comparative to the US and OD pretreated sample. Weibull model fitted well to the experimental results (R² > .99) than the first order. PRACTICAL APPLICATIONS: Ultrasound, osmotic dehydration, and osmosonication are unique pretreatment techniques that are widely used prior to drying of various agricultural products due to its numerous advantages over conventional methods. Its application in the drying of foods could help shorten the drying time, reduce processing costs, improve energy consumption and efficiency and preserve the physical and nutritional properties of the dried product. The outcomes of the present study will provide a better understanding of different nonthermal pretreatment methods and also make available more information for selecting pretreatment techniques for ginger drying.