Dextrin, protective action

Clearly, the smaller is the gold or rubin number, the more effective is the biopolymer at shielding the dispersion from coagulation by electrolytes. To describe this shielding phenomenon, Zsigmondy coined the term protective colloid ( Schutzkolloide ), which functions by protective action. From the results recorded in Table 2.1, it can be inferr that sodium casemate is considerably more effective in its protective action than is, say, dextrin or potato starch. Note that both of these latter polymers are nonionic in character. 

The albumin acts as a protective colloid for the casein and this explains the different behavior of the two substances. Several American medical men have realized this difference and favor the addition of protective colloids such as gum arabic, dextrin, etc., to cow s milk before giving it to children. Alexander has shown that cow s milk may be made to react much more like human milk if the protective colloids are added. Some authors have also claimed that casein from the two sources is not the same. This is probably due to the protective action of the albumin, because by dissolving the casein from human milk, and reprecipitating several times, it resembles more and more that from cow s milk. 

The only example of this technique applied to the amylose component is that already described, of the action of Z-enzyme on the /3-limit dextrin. In the case of amylopectin, enzymic methods enable a distinction to be made between the proposed laminated and highly ramified structures (I and III, in Fig. 1, page 352). The method used by Peat and coworkers101 involves the successive action of /3-amylase and R-enzyme on waxy maize starch. /3-Amylolysis will degrade A-chains down to two or three units from the 6 —> 1-a-D interchain linkages. These latter linkages will protect the... 

Several questions arise about the role of the acid catalyst in dextrinization. Such catalysts are known to promote a carbonium ion mechanism of sugar polymerization in which some rings can be opened. Perhaps, in the case of dextrinization, both the heterogeneity of the process and steric reasons protect the rings against attack by the acid. The nature of the acid catalyst and the mode of its interaction also play an essential role. The mild action of polyphosphoric acid in dextrinization was interpreted in terms of the possibility of its esterification with i>-glucosyl units. Some volatile adds. 

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