FTIR-based comparative analysis of glucomannan contents in some tuberous orchids, and effects of pre-processing on glucomannan measurement

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Acemi A. , Çobanoğlu O., Turker-Kaya S.

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, vol.99, pp.3681-3686, 2019 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 99
  • Publication Date: 2019
  • Doi Number: 10.1002/jsfa.9596
  • Page Numbers: pp.3681-3686


BACKGROUND: Glucomannan (GM) is a polysaccharide of the mannan family of compounds found in some plant species. The
dried and powdered tubers of some orchid species, collectively known as ‘salep powder,’ are a commercially important crop
for human consumption and are one of the primary sources of GM. GM content is the primary indicator for the yield and quality
of salep powder. We hypothesized that it would be more practical and accurate to measure GM content within tuber powder
directly, prior to any purification or pre-processing. The GM content of tubers of 14 different orchid species was evaluated
and compared using Fourier transform infrared (FTIR) spectroscopy and an enzymatic colorimetricmethod.
RESULTS:Amongthe analyzedmodes, thesumof the peak areas at 873 and 812cm−1,which represent theCHbending attributed
to the 𝜷-pyranose form of D-glucose and D-mannose, respectively, gave the only confirmation using colorimetric methods. It
was found that the tubers of Himantoglossum caprinumand Serapias vomeracea had the highest GM concentrations among the
analyzed species. After conducting different pre-processing steps on Serapias vomeracea tubers, it was found that treating the
tubers with milk, or high temperature resulted in an apparent increase in GMconcentrations.
CONCLUSION: Himantoglossum caprinum and Serapias vomeracea give the highest yields of GM and should be used for
commercial horticulture. GMestimation should bemade prior to any pre-processing. FTIR spectroscopy is effective and reliable
for directly comparing GM content of different orchid species, without the need for any purification or pre-processing.