Analysis of Structural Change in Keratin Fibers Resulting from Chemical Treatments Using Raman Spectroscopy

In the 2005 study, researchers used Raman spectroscopy to analyze the effects of chemical treatments on the structure of virgin white human hair, specifically during a permanent hair straightening process. They found that the cuticle and cortex of hair have distinct band shapes, with the cuticle being more amorphous. The reduction process significantly decreased the S-S band intensity on the hair surface but did not affect the hair center. Heating the keratin fibers after reduction did not alter this outcome. However, heating increased the amide III band intensity in the cortex, suggesting a shift to a random coil form in the proteins. Notably, about 95% of the broken S-S bonds were reformed after oxidation post-heating, with a slightly lower reconnection rate of 90% when oxidation followed reduction. The study concluded that heat treatment during hair straightening causes protein randomization in the cortex, which facilitates the reconnection of S-S bonds during oxidation.