Understanding the crystallization process in detergent formulations in the absence and presence of agitation

Detergents are used on a global scale and, therefore, are exposed to a wide range of temperatures and shear rates during distribution. At low and subzero temperatures crystallization may occur in the product. Manufacturers utilize a variety of methods to detect these crystal failures, typically involving the storage of formulations between −3 and 10 °C for up to 28 days. This paper describes the application of agitation as a route to reduce the time scale of the stability tests, thus increasing productivity. Agitation simulates vibrations that the formulations experience during distribution. In the absence of mixing, crystallization was found to originate from the air–liquid interface, whereas in the presence of mixing, the crystallization began around the mixing blade. The times to failure detected by the current and proposed methods correlated, indicating the potential for this novel approach to be used in stability testing.