Researchers and confectioners alike have known for years about sugar's finicky melting point, but have always attributed it to either impurities or their equipment. University of Illinois scientists, however, have discovered that the real reason is because sugar doesn't melt, it decomposes.
When a material, like say ice, melts, it does so at a consistent and repeatable temperature, and the process can be reversed — aka freezing. The melting point of sugar, however, depends on how hot the fire melting it is, known as heating-rate dependence. Also, the sugar can't be un-melted; its molecular structure is changed in a way that can't be reversed.
"We saw different results depending on how quickly we heated the sucrose. That led us to believe that molecules were beginning to break down as part of a kinetic process," Shelly J. Schmidt, a University of Illinois professor of food chemistry, told ACES News. She and her team used high-performance liquid chromatography to observe the sucrose both before and after melting and confirmed the presence of sucrose decomposition components as soon as the melting process began.
Because the rate of "Apparent Melting", as the process is now called, is dependent on the rate of heating, much like milk pasteurisation, it could prove a boon for numerous food and pharmaceutical industries.
"Certain flavour compounds give you a nice caramel flavour, whereas others give you a burnt or bitter taste. Food scientists will now be able to make more of the desirable flavors because they won't have to heat to a 'melting' temperature but can instead hold sugar over a low temperature for a longer period of time," said Schmidt, "This discovery is important to food scientists and candy lovers because it will give them yummier caramel flavors and more tantalising textures. It even gives the pharmaceutical industry a way to improve excipients, the proverbial spoonful of sugar that helps your medicine go down." [UoI ACES News via R&D Mag]