Surface modification via alginate-based edible coating for enhanced osmotic dehydration mass transfer of ginger slices

Abstract

Ginger has a high moisture content, which makes it highly susceptible to spoilage. Therefore, the shelf life can be extended through drying. In the drying process, osmotic dehydration is applied as pre-treatment due to its simple operation and energy-saving process for removing moisture from food. However, large solute gain during the osmotic dehydration has become the major challenge of this process as it has a negative impact on the final product. The edible coating is the key step to circumventing this issue. Alginate is a potential candidate for the coating material to enhance the mass transfer kinetics of the osmotic dehydration process. This study investigated the surface modification of ginger slices caused by the cross-linker calcium chloride and plasticizer glycerol on alginate coating using a Scanning Electron Microscope. Furthermore, the kinetics of water loss and solute gain were evaluated and modelling aspects were conducted. It was observed that the surface roughness of ginger coated with a combination of alginate, glycerol and calcium ions has reduced. This facilitated the mass transfer process, which was observed to have a high water loss and a lower solute gain. The Peleg model presented the best fitting model of mass transfer kinetics during osmotic dehydration of ginger slices. From this work, it can be deduced that alginate-based coating can be a promising pretreatment step in the osmotic dehydration process.