Water content, protein-based materials

In order to be able to describe and predict changes in the physical-chemical properties of proteins during dry processing according to temperature and RH, it is essential to construct the state diagram relative to the water (or plasticiser) content [3,174]. Figure 11.7 shows the different steps involved in the formation of protein-based materials using the dry process [13,136,152,175] ... 

Soy, and Other Legume Proteins Two quite different product types have been constructed by extrusion, high-density flaked structures for meat analogues, and lower density and crispy products for high-protein snacks. The latter uses conditions similar to that of starch-based cereal extrusion to obtain low bulk density in the expanded product the former uses a higher water content in the extruder barrel and lower exit temperatures to obtain a dense material with open pores or even flaked structmes. For these two types of processes, molecular changes in the extruder barrel are not dissimilar. Post-die structuring of the extrudates determines final product properties. 

The method is suitable not only for a rapid determination of free primary amino groups in seawater but can also be employed for an estimation of the combined amino nitrogen content of water samples and particulate matter. Butcher and Lowry (1976) employed o-phthalaldehyde after hydrolysis of different defined proteins and found a recovery of 70% based on the calculated amino acid content. Although when working with undefined protein-like material, the recovery is dependent upon the fluorescent response of the individual monomers released on hydrolysis, and also on the destruction losses. Maske (1979) claimed a recovery of 74% whilst using the method for plankton material after hydrolysis with 4 M HCl. 

The exclusion of water from the environment of a protein may provide resistance to chemical modification of the protein structure during processing and storage. Processes such as freeze-drying and spray drying have been employed to prepare solid-state dosage forms of pharmaceutical proteins with vastly reduced water content. Several theories of protein encapsulation in glassy materials have been proposed based on the three considerations mentioned in Section 6.4.2.3 ... 

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