Known physicochemical basis of some of these texturization processes are presented below:
1.Thermal Coagulation and Film Formation: Concentrated soy proteins can be thermally coagulated on a flat metallic surface, such as that of a drum dryer. Resulting thin, hydrated films can be folded, pressed together and cut.
2. Fiber formation: Fiber spinning of vegetable (especially soy) and milk proteins bears many similarities to the spinning of synthetic textile fibers. It is usually necessary to start from isolates containing 90% protein or more. Four to five successive operations are necessary and can be done continuously.
3. 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.