23 research outputs found
Raman imaging of changes in the polysaccharides distribution in the cell wall during apple fruit development and senescence
Main conclusion
Du ring on-tree ripening, the pectin distribution changed from polydispersed in cell wall to cumulated in cell wall corners. During apple storage, the pectin distribution returned to evenly dispersed along the cell wall.
The plant cell wall influences the texture properties of fruit tissue for example apples become softer during ripening and postharvest storage. This softening process is believed to be mainly connected with changes in the cell wall composition due to polysaccharides undergoing an enzymatic degradation. These changes in polysaccharides are currently mainly investigated via chemical analysis or monoclonal labeling. Here, we propose the application of Raman microscopy for evaluating the changes in the polysaccharide distribution in the cell wall of apples during both ripening and postharvest storage. The apples were harvested 1 month and 2 weeks before optimal harvest date as well as at the optimal harvest date. The apples harvested at optimal harvest date were stored for 3 months. The Raman maps, as well as the chemical analysis were obtained for each harvest date and after 1, 2 and 3 months of storage, respectively. The analysis of the Raman maps showed that the pectins in the middle lamella and primary cell wall undergo a degradation. The changes in cellulose and hemicellulose were less pronounced. These findings were confirmed by the chemical analysis results. During development changes of pectins from a polydispersed form in the cell walls to a cumulated form in cell wall corners could be observed. In contrast after 3 months of apple storage we could observe an substantial pectin decrease. The obtained results demonstrate that Raman chemical imaging might be a very useful tool for a first identification of compositional changes in plant tissue during their development. The great advantage Raman microspectroscopy offers is the simultaneous localization and identification of polysaccharides within the cell wall and plant tissue
Vapor grown carbon nanofiber based cotton fabrics with negative thermoelectric power
Vapor grown carbon nanofiber (CNF)
based ink dispersions were used to dip-coat woven
cotton fabrics with different constructional parameters, and their thermoelectric (TE) properties studied
at room temperature. Unlike the positive thermoelectric power (TEP) observed in TE textile fabrics
produced with similar carbon-based nanostructures,
the CNF-based cotton fabrics showed negative TEP,
caused by the compensated semimetal character of the
CNFs and the highly graphitic nature of their outer
layers, which hinders the p-type doping with oxygen
groups onto them. A dependence of the electrical
conductivity (r) and TEP as a function of the woven
cotton fabric was also observed. The cotton fabric with
the largest linear density (tex) showed the best
performance with negative TEP values around
- 8 lV K-1
, a power factor of 1.65 9 10-3
lW m-1 K-2
, and a figure of merit of 1.14 9 10-6
.
Moreover, the possibility of a slight e- charge transfer
or n-doping from the cellulose onto the most external
CNF graphitic shells was also analysed by computer
modelling. This study presents n-type carbon-based
TE textile fabrics produced easily and without any
functionalization processes to prevent the inherent
doping with oxygen, which causes the typical p-type
character found in most carbon-based TE materialsFEDER funds through
COMPETE and by national funds through FCT â Foundation for
Science and Technology within the project POCI-01-0145-
FEDER-007136. E. M. F. Vieira is grateful for financial support
through FCT with CMEMS-UMinho Strategic Project UIDB/
04436/202
The Influence of High-Intensity Ultrasonication on Properties of Cellulose Produced from the Hop Stems, the Byproduct of the Hop Cones Production
The goal of this work is to evaluate the hop stems, a byproduct of hop cones production, as a potential source of cellulose. Hop stems contain up to 29% of cellulose. The cellulose isolation was conducted through the thermochemical treatment. After high-speed blending, the cellulose was characterized by 67% of crystallinity degree obtained from X-ray diffraction and median diameter of 6.7 nm obtained from atomic force microscopy imaging. The high-intensity ultrasonication (HIUS) was applied to reach further disintegration of cellulose fibers. The longer HIUS treatment resulted in decrease in crystallinity degree even up to 60% and decrease in the fiber diameter up to 4 nm. The Fourier transform infrared spectroscopy (FTIR) spectra showed that HIUS treatment led to changes in intermolecular hydrogen bonds. The stability of cellulose dispersions versus length of HIUS treatment was monitored over 14 days with back dynamic light scattering and laser Doppler electrophoresis methods. Obtained results are evidence that the hop stems are a potential source of cellulose and that it is possible to obtain stable dispersions after HIUS treatment. This was the first time that the properties of hop cellulose have been described so extensively and in detail after the use of HIUS treatment