The degumming of silk fabrics: a preliminary near infrared study

The silk filament spun by the silkworm (Bombyx mori) is composed of two fibroin filaments held together by a cementing layer of sericin. Fibroin and sericin account for about 75 w% and 25 w% of the raw silk, respectively. The degumming process involves removing the sericin layer prior to dyeing. Generally, it makes use of a solution containing soap, synthetic detergents or proteolytic enzymes. A set of 50 protease degummed silk fabrics (crepe) with different weight losses were analysed by means of near infrared (NIR) spectroscopy. A correlation between degumming loss (SE=0.312%) and NIR spectra was obtained using the principal component regression (PCR) algorithm. The correlation obtained had a coefficient of determination (RI) of 0.97 and a standard error of calibration (SEC) of 1.6% for a mean value of 14.6%. In the second part of the study, NIR spectroscopy was used to determine the concentration of sericin in solution. A set of sericin aqueous solutions ranging from 20 g L-1 to 200 g L-1 was prepared and the spectra were acquired in transilectance mode between 10000-3700 cm(-1) and correlated with corresponding sericin concentration values. The correlation obtained between specified sericin concentration values and values estimated by NIR spectra had the statistics R-2 of 0.99 and SEC of 4.9 g L-1 for an average sericin concentration of 103.8 g L-1. The assignment of characteristic NIR spectral bands of sericin and fibroin was made.