X‐ray diffraction of gelatin fibers in the dry and swollen states

The aim of this x‐ray diffraction investigation is to establish a comparison between the structure of collagen and that of gelatin gels. The gelatin gels are drawn into fibers, which are dried before use. The xray scattering patterns of the gelatin fibers show a close analogy with collagen, which provides evidence for the presence of bundles of triple helices in the dried, oriented gels. The mechanisms of swelling of the gelatin fibers are identified by investigating the humidity‐sensitive position of the equatorial spots related to the side‐by‐side distance D of the triple helices. The distance D increases continuously as more water is added to the fibers; this is accompanied by a progressive loss of orientation of the triple helices with respect to the fiber axis. The temperature dependence of the x‐ray patterns is also investigated. We discuss the implications of this study for understanding the gelation mechanisms and the structure of gelatin gels. Comparisons are made with other physical gels.