"Purplish Blue" or "Greenish Grey"? Indigo Qualities and Extraction Yields from Six Species

Anna Hartl; Andrea Polleichtner; Johannes Novak

doi:10.3390/plants13070918

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Title (eng)

"Purplish Blue" or "Greenish Grey"? Indigo Qualities and Extraction Yields from Six Species

Author

Anna Hartl

Andrea Polleichtner

Johannes Novak

University of Veterinary Medicine Vienna

Abstract (eng)

Indigo quality is determined by its indigotin content. Another quality indicator is colour. For an evaluation of species, indigo samples from Indigofera tinctoria, Indigofera suffruticosa, Indigofera arrecta, Persicaria tinctoria, Strobilanthes cusia and Wrightia laevis cultivated in Austria and China were visually classified and analysed spectrophotometrically and using a L*a*b* measuring device. In addition to a standardised hot-extraction method without lime, some samples were extracted simulating traditional methods at ambient temperatures using lime. The highest indigotin contents were achieved with Indigofera arrecta (55%, Austria) and Strobilanthes cusia (56%, China). There were no statistically significant differences between the indigo extraction yields of the species cultivated in Austria, but Indigofera arrecta and Persicaria tinctoria had statistically significantly higher indigotin extraction yields than Indigofera tinctoria and Indigofera suffruticosa. From the species extracted in China, Strobilanthes cusia showed higher values in all parameters than Indigofera tinctoria, Indigofera suffruticosa and Wrightia laevis. Compared with the standardised method, the method simulating local practice yielded more indigo but had a lower indigotin content; the indigotin extraction yields did not differ greatly. L*a*b* values enabled precise estimations of the indigotin content, making it an interesting option for quality control, as inexpensive, easy-to-handle L*a*b* measuring instruments have become available.

Keywords (eng)

Natural IndigoIndigotinNatural DyeEthnobotanyExtraction YieldSpectrophotometryL*a*b*Colour MeasurementIndigo Quality

Type (eng)

journal article

Language

[eng]

Persistent identifier

https://phaidra.vetmeduni.ac.at/o:4359

DOI

10.3390/plants13070918

Is in series

Title (eng)