Alkaline Degradation of Sucrose

Richards et al.23-24 proposed that the alkaline degradation reaction proceeds via a slow, rate-determining SJCB mechanism, where the substitution at the C-l of the D-glucose moiety by oxyanions derived from l -OH or 3 -OH resulted in 1- or 3-O-P-D-glucopyranosyl-D-fructose (see Fig. 4) the mechanism implies that T - time thyl sucrose is degraded via 3 -displacement and 3 -(3-methylsucrose via the 1 -displacement. The 1- or 3- 3-[3-D-glucopyranosyl-D-fructose intermediates are then 

Sucrose can, however, degrade to D-glucose and D-fructose in slightly alkaline solution at pH up to 8.3 (sucrose is most stable611 at pH 8.3-8.5, although the reason for this requires some elucidation), but this degradation proceeds by the normal acid-hydrolysis mechanism. In sucrose manufacture, therefore, the main reaction causing sucrose loss, between pH 7 and about 8.3, is the same acid hydrolysis that occurs at lower (acid) pH. 

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The final chapter, by Clarke, Edye, and Eggleston (New Orleans, Louisiana), deals with the centuries-old technological problem of maximizing yield in the extraction of sucrose from cane or beet juice. Somewhat remarkably, important misconceptions about the fundamental aspects of alkaline degradation of sucrose still persist. The authors of this chapter effectively interpret traditional sugar technology, based largely on empirical art, in clear terms of accepted fundamental principles of chemistry. 

Further work on the mechanism of the alkaline degradation of sucrose, using substituted derivatives, supported an earlier hypothesis which invoked l-0-j3-D-glucopyranosyl-D-fructose as an intermediate (Scheme 5). ... 

Because alkali degradation of sucrose does not result in inversion products, in slightly alkaline solution (pH < 8.5), the loss of sucrose to invert sugar (glucose + fructose) is a consequence of the acid hydrolysis mechanism, which provides D-glucose and D-fructose for further alkaline degradation. 

Alkaline Degradation. At high pH, sucrose is relatively stable however, prolonged exposure to strong alkaU and heat converts sucrose to a mixture of organic acids (mainly lactate), ketones, and cycHc condensation products. The mechanism of alkaline degradation is uncertain however, initial formation of glucose and fructose apparendy does not occur (31). In aqueous solutions, sucrose is most stable at —pH 9.0. 

Sucrose Sucrose acrylate was chemoetiTyraatically synthesized and crosslinked by ethyleneglycol (liinethacrylate or yi3-ni( tbylglucoside 2,(>diacrylate. Degradation of the pendent sucrose by a alkaline protease, Proleather. Potential use as water absorI >ents. Dordick el at., 1993, 199.5... 

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