Abstract

Pineapple is a well-known reservoir of proteases. Treatment of silk skeins with pineapple juice resulted in degumming of the fibers leading to unmasking of the lustrous inner layer. The juice obtained from raw pineapple was subjected to concentration by saturation with 85% ammonium sulfate. The proteolytic activity of the juice as well as the concentrate was found to effectively degum the skein. The proteases were optimally active at pH 6.6, and 50-55 C. Treatment of the skein with 5U of proteolytic activity at 50 C and pH 6.6 for 120min resulted in weight loss to an extent of 17-18.5%. Release of peptides and amino acids, arginine, histidine and aromatic amino acids was monitored during the process of degumming. The rate of release of peptides and amino acids was relatively higher till 90-120min, reducing thereafter. The enzymatically degummed skeins were found to be more lustrous in comparison to untreated skeins. Conventionally, raw silk skeins are chemically treated to impart luster to the fiber. Enzymatically degummed fibers displayed smoother texture and improved stretch ability in comparison to chemically decoated skeins. Use of pineapple in silk manufacture may boost the agronomy in tropical regions where it is grown extensively.

Keywords: Degumming; Silk skein; Silk proteins; Pineapple juice; Proteolytic activity; Luster; Amino acids

Abbreviation: TLC: Thin Layer Chromatography