Thermoplastic starch extrusion-cooking

Thermoplastic starch extrusion-cooking is associated with a rather low energy input 0.07 kWh kg on average. The extruder power required for extrusioncooking of TPS depends on material composition an increase in the glycerol content in a mixture causes the process energy consumption to decrease. 

The thermoplastic amorphous starch is produced using the extrusion cooking technology,... 

This article reviews the main results obtained in the fields of starch-filled plastics and thermoplastic starch, with particular attention to the concepts of gelatinization, destructurization, extrusion cooking, and the complexation of... 

Moscicki L, Mitrus M, Wojtowicz A, Oniszczuk T, Rejak A, Janssen L. Appbcation of extrusion-cooking for processing of thermoplastic starch (TPS). Food Res Int 2012 47 291-299. 

Starch-based polymers have been intensively studied for their extrusion characteristics, since extrusion processing plays a primary role in establishing the polymer s properties. Starch can be made thermoplastic using technology very similar to extrusion cooking [13]. Granular beads of starch are approximately 15-100 pm in diameter and can be blended as a filler with other polymeric materials [91]. Under special heat and shear conditions during extrusion, starch can be transformed into an amorphous thermoplastic material by a process known as destructurisation. 

In the patent literature the term destructurized starch has been used [71-85] to refer to a form of thermoplastic starch described as molecularly dispersed in water [86]. Other patents [17, 87-91] use the term destructured starch to describe a thermoplastic starch which is treated by extrusion cooking to distinguish it from gelatinized starch, processed in presence of high amounts of water. Furthermore a recent USDA s paper [92] on this subject concludes that destructurized starch is not a new or novel entity but is merely another term used to describe the well-known disordering of starch chains and the melting of crystallites that take place when starch is heated in the presence of limited amounts of water . Henceforth extrusion-cooked starch will be reported as thermoplastic starch. 

This chapter reviews the main results obtained in the fields of starch-filled plastics and thermoplastic starch with particular attention to the concept of gelatinisation, destructurisation, extrusion cooking, and the complexation of amylose by means of polymeric complexing agents with the formation of specific supra-molecular structures. The behaviours of products now in the market are considered in terms of processability, physical-chemical and physical-mechanical properties and biodegradation rates. 

Mitrus, M. (2005) Changes of specific mechanical energy during extrusion cooking of thermoplastic starch. TEKA Komisji Motoryzacji i Energetyki Rolnictwa,... 

Thermoplastic extrusion Name of the continuous extrusion process in which raw materials, generally refined milled fractions, are cooked and plasticized due to heat and pressure occurring inside the extruder barrel. The starch is gelatinized, and the exiting extrudate is usually formed into predetermined shapes. This process is widely used to produce direct-expanded-products and pellets or intermediate products used for production of many breakfast cereals and snacks. 

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