Investigation of surface modification of casein films by rennin enzyme action using micro-beam grazing incidence small angle X-ray scattering.

摘要

Micro-beam grazing incidence small angle X-ray scattering ( muGISAXS) scans were performed to investigate structural changes that occur on a casein film after deposition of a droplet of rennin (chymosin). Subsequent diffusion of the droplet into the film led to a lateral and vertical concn. gradient of rennin. As a result of the enzyme action, the film surface became roughened and the formation of islands evident. The altered surface morphology led to a variation in the muGISAXS pattern, more precisely to the occurrence of a 2nd so-called Yoneda peak. As for the untreated casein film, the mean size of the micelle components (casein micelles, substructure and colloidal calcium phosphate) remained constant within the rennin droplet area. In contrast, a broadening of their corresponding size distributions could be detected. Potential of GISAXS scanning experiments with mum-sized X-ray beams is discussed, in view of problems with the interpretation of the data obtained from imaging techniques such as atomic force microscopy.