The Degumming of Silk Fabrics: A Preliminary near Infrared Spectroscopy Study

Abstract

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 (crêpe) 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 ( R2) 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 transflectance 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 R2 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.