Discrimination between an indigo dyeing produced by the reduction with hydrosulfite and that produced by fermentation

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09680046
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 家政学
• Research Institution: Mukogawa Women's University
• Principal Investigator: USHIDA Satoshi School of Human Environmental Sciences, Mukogawa Women's University, 生活環境学部, 助教授 (40176657)
• Project Period (FY): 1997 – 1998
• Keywords: natural dye / indigo / indigo dyeing / fermentation vat / hydrosulfite / ハイドロ建て

Research Abstract

Indigo must be reduced under alkaline conditions before dyeing. Traditionally fermentation has been utilized for the reduction of natural indigo dye. However, at recent times chemical reagents such as sodium hydrosulfite is sometimes used for indigo dyeing with natural indigo. The purpose of the research is to discriminate an indigo dyeing produced by the reduction with hydrosulfite from that produced by fermentation.
Perreduced substances can be produced by the reduction of indigo with hydrosulfite because of its strong reducing power. Impurities in commercial indigo and in reoxidized indigo which is submitted to the reduction with hydrosulfite was compared using HPLC. Among many impurities, colorants are convenient to detect. A colorant (absorption maximum = 600nm) which is present in commercial indigo but is not present in reoxidized indigo was found. However the detection of this colorant was not reproducible. Then other impurities besides colorants were examined. Because of the variety and the badness of separation of such impurities, the discrimination between an indigo dyeing produced by the reduction with hydrosulfite and that produced by fermentation is in progress.