Due to the increasing concerns about environmental degradation and the limited availability of oil, there has been a significant push to find substitutes for petroleum-based plastics. In recent years, there has been a growing interest in using starch resources in non-food applications. Starch is advantageous because of its low cost, wide availability, and total compostability without leaving any toxic residues. Additionally, it can be processed by traditional polymer processing techniques, such as extrusion, without significant modification.
However, natural raw starch exists in granules with a complex multiscale structure, making it difficult to produce starch-based materials. To create these materials, the raw starch must undergo thermal processing with a plasticizer, usually water, to cause a phase transition and disrupt its native granule structure. This process, known as plasticization of starch, is more complex than that of standard synthetic polymers.
Control of the rheological behavior of plasticized starch during processing is important to avoid fundamental flow-related engineering problems and to ensure the final product meets quality requirements. Different processing techniques require different operating conditions. Rheological characterization of plasticized starch is a challenging task due to the issues related to sampling homogeneity and consistency, as well as handling the high melt viscosity of the plasticized starch.
This series aims to summarize the three most important aspects of starch thermal processing: the native multilevel structure of starch, the thermal phase transition of starch, and the rheological behavior of starch. Additionally, it reviews state-of-the-art processing strategies and techniques for producing different kinds of plasticized starch-based products, such as films, foams, and shaped articles. The information provided in this chapter is critical to anyone working in the field of starch processing and will be instrumental in the future development of starch-based materials for food packaging and other new applications.