Melting Sucrose

Cane sugar is generally available ia one of two forms crystalline solid or aqueous solution, and occasionally ia an amorphous or microcrystalline glassy form. Microcrystalline is here defined as crystals too small to show stmcture on x-ray diffraction. The melting poiat of sucrose (anhydrous) is usually stated as 186°C, although, because this property depends on the purity of the sucrose crystal, values up to 192°C have been reported. Sucrose crystallines as an anhydrous, monoclinic crystal, belonging to space group P2 (2). 

Disaccharides like maltose, lactose, and trehalose are used for their similarity to sucrose, but with differences in some properties, such as sweetness, melting point, or hygroscopicity. 

A useful summary of sucrose losses under good conditions was presented in the symposium by Latham,65 as follows, for percent on melt solids ... 

A stoicheiometric mixture with sucrose ignites at 159°C, and has been evaluated as a rocket propellant [1], Dry powdered mixtures with glucose containing above 50% of chlorate explode under a hammer-blow [2], Pyrotechnic mixtures with lactose begin to react exothermally at about 200°C, when the lactose melts, and carbon is formed. This is then oxidised by the chlorate at about 340° C. The mechanism was studied by DTA [3],... 

De Luca et al. [1.48] showed, that the addition of 5 % tertiary butyl alcohol (tBA) to aqueous sucrose and lactose solutions (up to 40 %) resulted in a frozen matrix, which could be easily freeze dried. De Luca demonstrated by DSC that the melting point rose distinctly (with 60 % solution to -10 °C), but the endothermic of melting returned to 25 %, indicating that not much water had frozen. In solutions with 5 % tBA the exothermic of crystallization became more visible and the melting of tBA could be recognized. 

Figure 13.4 Perturbation of the melting transition temperature of a single domain protein as a function of benzyl alcohol content (described as % B.A.). The liquid protein formulation consists of 10 mM Tris, 4% mannitol, and 1% sucrose, pH 7.4. (Permission to use the figure granted by BioPharm.)...

Konig and co-workers also reported that Amberlyst 15 can promote the dehydration of carbohydrates to HMF using safe concentrated low melting mixtures consisting of choline chloride (ChCl) and about 50 wt% of carbohydrates. From fructose, glucose, sucrose, and inulin, HMF was produced with 40, 9, 27, and 54%, respectively within 1 h of reaction at a temperature around 100°C. Montmorillonite has also been used as a solid acid catalyst affording HMF with 49, 7, 35, and 7% yield from fructose, glucose, sucrose, and inulin, respectively [97]. 

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