Unconventional media and technologies for starch etherification and esterification

Among the most widespread starch derivatives, etherified and esterified starches play an important role. These derivatives are generally prepared by using thermal energy and conventional solvents. This review summarizes the recent advancements in the etherification and esterification of starch in unconventional media, i.e. ionic liquids or supercritical CO2, and by employing unconventional technologies, i.e. microwaves, ultrasounds or ball-milling. The present contribution aims to provide an overview to help researchers seeking an alternative medium or technology to functionalize starch. The green aspects of unconventional approaches are presented and the physical-chemical properties of modified starches obtained by these approaches are also described. Whenever possible, the advantages and disadvantages of each system are discussed. Finally, even if it is not always mentioned in the publications, the use of these experimental conditions probably leads to a partial degradation of the starch molecular structure.