Characterization of Secondary Structure of Pig Hair Fiber Using Fourier-transform Infrared Spectroscopy

Hair or bristle is one of the key by-products of humane slaughter of pigs. In the present study, Fourier-transform infrared (FTIR) spectroscopy was used for examining protein secondary structure of hair fiber from different breeds of pigs (Ghungroo, Ninag Megha, Hampshire, and Duroc). Prominent amide I (1635-1648 cm(-1)) and amide II (1517-1528 cm (-1)) bands could be observed in the spectra. Differences in presence/absence of certain FTIR bands between breeds suggests influence of genetic background in the structure of hair fiber. Deconvolution resolved secondary structure of protein in amide I region of spectra into corresponding alpha-helix (38.0 +/- 2.9%), beta-sheets (32.2 +/- 2.0%), beta-turns (19.4 +/- 3.1%) and unorganized structural components (10.3 +/- 2.5%). Heating of fibers from 80 degrees C to 120 degrees C resulted in changes in amide regions and alpha-helix to beta-sheet ratio of amide I band. Further, correlations were calculated between area under the curve of various FTIR bands and tensile properties of the fiber. Area of FTIR band at 1635 cm (-1) was positively correlated with tenacity, initial modulus, extensibility, and work of rupture (r = 0.30 to 0.39). In nutshell, the study reveals subtle differences in secondary structure of hair with respect to breed or temperature treatment and suggests relation between FTIR spectral characteristics and tensile properties.