Explain about the Thermoplastic Extrusion?

This is a major technique used for vegetable proteins at present. Thermoplastic extrusion leads to dry fibrous and porous granules or chunks, (rather than fibers) which upon rehydration, possess a chewy texture. Starting material need not to be protein isolates, thus less costly protein concentrates or flours (containing 45-70% protein) can be used. Casein or gluten can be added as such. Addition of small amount of starch or amylose improves the final texture, but a lipid content above 5-10% is detrimental. Addition of 3% sodium chloride or calcium chloride also firms the texture. Good texturization by this process requires proteins with appropriate initial solubility, high molecular weight and development of proper plasticizing and viscosity properties of protein-polysaccharide mixture within the dye.