ISSN:
1573-904X
Keywords:
amorphous
;
sucrose
;
acid-catalyzed
;
residual water
;
solid-state degradation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Purpose. Factors affecting the solid-state acid-catalyzed inversion ofamorphous sucrose to glucose and fructose in the presence ofcolyophilized citric acid, with less than 0.1% w/w residual water, have beenstudied. Methods. Samples of citric acid and sucrose were lyophilized at aweight ratio of 1:10 citric acid:sucrose from solutions with initial pHvalues of 1.87, 2.03, and 2.43, as well as at a weight ratio of 1:5, atan initial pH of 1.87. Glass transition temperatures, Tg, were measuredby DSC and the presence of any possible residual water was monitoredby Karl Fischer Titrimetry. The inversion of sucrose was measured bypolarimetric analysis after reconstitution of solid samples stored at50°C under P2O5. Results. Samples of 1:10 citric acid:sucrose at an initial pH of 1.87,2.03, and 2.43 exhibited the same Tg. The initial rate of reactivity wasaffected at a 1:10 ratio by the solution pH before lyophilization in theorder: 1.87 〉 2.03 〉 2.43 and by citric acid concentration at pH 1.87in the order 1:5 〉 1:10. Conclusions. Sucrose, colyophilized with an acid such as citric acid,undergoes significant acid-catalyzed inversion at 50°C despite the verylow levels of residual water, i.e., 〈0.1% w/w. At the same ratio ofcitric acid to sucrose (1:10), and hence the same Tg, the rate of reactioncorrelates with the initial solution pH indicating that the degree ofionization of citric acid in solution is most likely retained in the solidstate. That protonation of sucrose by citric acid is important is shownby the direct relationship between maximum extent of reaction andcitric acid composition. It is concluded that colyophilization of acidicsubstances with sucrose, even in the absence of residual water, canproduce reducing sugars capable of further reaction with otherformulation ingredients susceptible to reaction with reducing sugars.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1007517526245
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