Thermoplastic Starch: A Possible Biodegradable Food Packaging Material—A Review

In the past years, research has been focused on biodegradable materials to replace petroleum based plastics for food packaging application. For this purpose, biopolymers are considered the most promising material because of their biodegradable nature and long shelf life properties like resistance to chemical or enzymatic reactions. Starch is renewable, cheap, and abundantly available biopolymer. However, the intermolecular forces and hydrogen bonds in starch resist it to be processed as a thermoplastic material. To overcome this issue, different plasticizers are used to have deformable thermoplastic material called thermoplastic starches (TPSs). A plasticizer enhances the flexibility, the process stability of starch below the degradation temperature. Plasticizer lowers the glass transition temperature (Tg). TPS is very promising among the biobased materials available for the production of biodegradable plastic. TPS have some limitations; bad mechanical properties and water sensitivity. Starch absorbs water under higher relative humidity. This work will provide an outline about the research that has been done on TPS during last 15 years as biodegradable food packaging material. PRACTICAL APPLICATIONS: The basic role of food packaging material is to make it cost effective that satisfies industry requirements and consumer desires, and provide protection from three major classes of external influences: chemical, biological, and physical, e.g., such as exposure to gases, barrier to microorganisms, or from mechanical damage, respectively. These external influences may damage the quality of the food and shelf life. For this motive, starch has become the most preferred option among the verified classes of synthetic and natural materials. Retrogradation of starch chains in presence of water make it impossible to be use as packaging material. To overcome this issue, Starch has been plasticized with water and low molecular weight additive that can interact with its backbone by hydrogen bonding to produce thermoplastic starch (TPS). The objective of this review is to summarize numerous studies related to interaction of plasticizers and starch for the production of biodegradable TPS food packaging materials.