By: Anne Vuorema


Research Scientist Anne Vuorema of MTT AgrifoodResearch Finland proves in her doctoral dissertation that glucose can serve asa reducing agent of indigo. This finding is significant for devising moreecological dyeing practices for the textile industry.


Indigo is a vat dye and it needs to be reducedto its water-soluble leuco-form before dyeing. This allows the actual dye topass on to textile fibres. Glucose is known to be a good reducing agent, andVuorema's work demonstrates that it also works with indigo.


Glucose dyeing seems to suit plant-derivedfibres, such as cotton and flax, which withstand a high pH (11-12). However, atthis stage it cannot be recommended for animal fibres, such as wool and silk(which can only withstand a pH of up to 9).


A specialized field with few experts


Anne Vuorema's field of study is not widelyknown, and there are perhaps only 20 researchers worldwide whose work focuseson plant-derived indigo. Vuorema and MTT launched the indigo research as partof the EU Spindigo project in 2001-2004. The project prompted questions whichVuorema attempted to answer in her dissertation.


Vuorema works as an external researcher for MTTPlant Production Research. The Finnish Cultural Foundation granted ascholarship for her doctoral dissertation in three years. In 2007, the Academy of Finland funded her research at the University of Bath in England. This is where shehas conducted most of her electrochemical research. Vuorema conducted herresearch at the University of Bath and the University of Reading in 2004-2006.Professor Philip John at the University of Reading was the leader of theSpindigo project and he also supervised Vuorema's research in Reading.


Anne Vuorema's research provides answers thatenable researchers to improve the extraction of indigo from the leaves of dyer'swoad (Isatis tinctoria L.). Her work enhances the energy efficiency of dyeingand can potentially promote the profitable use of plant-derived indigo.


Dyer's woad is the best known of all indigo-producingplants in Europe. Plant-derived indigo was commonly produced until the early 20thcentury when synthetic indigo replaced it. The blue dye used in jeans, forinstance, is nowadays synthetically produced from oil, in a process whichwastes non-renewable natural resources and burdens the environment withsynthetic chemicals.


Electrochemical reduction enables a cleanprocess


In her dissertation research, Anne Vuoremadeveloped a new electrochemical method for determining the purity of indigo.She reduced plant-derived indigo using glucose and measured the indigoconcentration in the mixture using a new method. This is a great improvement indetermining the purity of plant-derived indigo.


The method can also be applied to assess thepurity of other similar chemicals.


"The degree of purity of plant-derivedindigo is fairly low. Crude indigo has a dye content of less than 50%, whilesynthetic indigo has a dye content of over 95%. The impurities and means toreduce them are not yet well known," Vuorema explains.


Businesses look for guaranteed standard qualityof dye. At the same time, ecologically geared companies are looking forincreasingly natural methods for dyeing fabrics, among other things.


 

"Plant-derived indigo is a marginal, alternative product, and it does not currently compete with synthetic indigo," Vuorema says. Vuorema also investigated indirect electrochemical reduction. She discovered that 1.8-dihydroxyanthraquinone was an efficient catalyst for glucose-induced reduction. Electrochemical reduction can only be introduced by major companies as it requires investment in special equipment.


"We still need to achieve a lower pH in glucose reduction and solve the matter of impurities," Vuorema muses.


Anne Vuorema's doctoral dissertation, Reduction and Analysis Methods of Indigo, was publicly reviewed at the University of Turku on 19th December 2008 at midday. Professor Bernd Rudolph of the University of Applied Sciences Jena will serve as the opponent and Professor Keijo Haapakka of the University of Turku as custos.


About the Author


The author is the Research Scientist at MTT Agrifood Research Finland.