Characterization of aspartame crystals

It is known that rodlike crystals of aspartame, in which several needle crystals appear to be bundled together (bundlelike crystals), obtained from nonstirred crystallization have remarkably improved physicochemical properties compared with crystals (needlelike crystals) obtained from conventional stirred crystallization. For example, bundlelike crystals have much better thermal stabilities than the needlelike crystals. The difference of thermal stabilities between these crystals could not be explained only by their different crystal sizes, because it still remained even when these crystals were adjusted to have the same crystal size. Characterization of these crystals was carried out using powder X-ray diffraction. It is found that bundlelike crystals have different crystal texture compared with needlelike crystals. It is indicated that differences of crystal texture between these crystals are caused by crystallizing conditions, that is, stirred or nonstirred. It was concluded that differences of physicochemical properties are a reflection of crystal texture, i.e., crystallinity and preferred orientation.