Hydrolytic degradation Molecular weight reduction

Certain enzymes may degrade specific bonds as illustrated in Fig. 21.11. Esters and ester derivatives can, however, also be degraded by conventional hydrolysis. The initial degradation involves a random, non-enzymatic hydrolytic ester cleavage, leading to rapid molecular weight reductions (i.e., bulk erosion). In this process, both the molecular mass as well as the crystallinity play a pivotal role [109]. 

A simplified alkali lability method has been employed in the author s laboratory, whereby the rate of alkali degradation is estimated from the amount of acidic substances produced by alkali degradation. This is expressed as alkali number, and represents the ml. of 0.1 N acid formed from 1 g. of the starch substance under specified conditions of alkali digestion. It is entirely an arbitrary value, and cannot be construed as an absolute measurement of aldehyde content or of molecular weight. It serves only to indicate whether the aldehyde content of the starch has remained constant, or whether it has increased or decreased. Farley and Hixon have found that the alkali number detects hydrolytic changes in the starch before they are measurable by copper or ferri-cyanide reduction. 

---