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0Study of pearl barley by THz high resolution spectroscopy
V. Vaks12, V. Anfertev12, E. Domracheva12, M. Chernyaeva12, A. Chernyaeva1
1-Institute for Physics of Microstructures RAS, 603950, Russia, Nizhny Novgorod, GSP-105 2- Lobachevsky University, 603022, Russia, Nizhny Novgorod, Gagarina av., 23
Nowadays spectroscopic analytical methods, operating in the frequency ranges from microwave to ultra-violet as well as other physic-chemical methods (mass-spectrometry, gas or liquid chromatography, microscopy etc.) are used for various applications (biology, medicine, agriculture etc.). One of the main problems of crop production and the food industry is fungal infections of grain. Diseases of grain crops lead to both plant death and loss of yield (for example, reduced germination of seeds, quality indicators of grain - loss of grain weight due to pathogenic damage, decreased nutritional and taste properties of grain, etc.). A number of metabolites produced by fungi are toxic to humans. Fungal diseases affect both plants as a whole and individual parts of plants (roots, stems, leaves, grains). Spread occurs both through the soil and through infected grain. The diagnostics of fungal infections of grain crops and the fight against them are current of importance for modern crop production and the food industry. The methods of high resolution terahertz (THz) gas spectroscopy are prospective for analysis of multicomponent gas mixtures and allow to reveal the metabolites of grain. The work is devoted to analyzing the metabolites composition of the barley grain by high-resolution THz spectroscopy.
A THz spectroscopy based on nonstationary effects such as inducing and decaying the free dumping polarization in a gas sample at the interaction of radiation and gas molecules can be considered as a high sensitive method of investigating the multicomponent gas mixtures. The devices can be realized in phase switching or fast sweeping modes of the probing radiation. The spectrometers with phase switching or with fast frequency sweeping developed by the authors, operating in the range of 118-178 GHz, were used. The sensitivity of the recorded absorption coefficient for these spectrometers at a cell length of 1 m is from 10-7 cm-1 to 5*10~8 cm-1. The THz gas spectroscopy method allows to detect volatile compounds, in a multicomponent gas mixture (vapors and products of thermal decomposition), including ones of biological origin. Therefore, it is promising to study the volatile compounds (products of thermal decomposition of macromolecules) as secondary metabolites of starch, sugars etc., that appear when the sample is heated. The thermal decomposition products of pearl barley as refined barley was studied. Some of substances with high quantities of absorption lines in operating frequency range of spectrometer such as glycolaldehyde, acetaldehyde, propanediol (two isomers), phenylpropienitrile, urea, acetone, hydroxyacetone, acetic acid, vinyl cyanide, butyl cyanide, isopropyl cyanide, alanine appeared in products of thermal decomposition of samples. More than some hundred absorption lines of these substances were detected in frequency range of 118-175 GHz. The composition of metabolites of pearl barley can be used for comparing with the composition of unrefined grain of barley for revealing the parts of molecular content concerning with the common substances and rest specified for pathogens including fungus.
These results demonstrate the promise of THz spectroscopy based on nonstationary effects for applications in agriculture and food industry.
This research was carried out under the State Assignment FFUF-2024-0024.
