共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
Oil pumpkin (Cucurbita pepo L. var. Styriaca) is an economically important horticultural plant cultivated for oil production. After harvesting seeds, the residual biomass
has a limited application and is usually left in the field. An experimental study was performed to evaluate the chemical composition
of the seeded fruit oil pumpkin biomass (OP) dried by solvent-exchange using ethanol. The sugar composition of polysaccharides
obtained by sequential extraction with water and dilute alkali indicated the prevalence of pectic polysaccharides. Hemicelulloses
were released in higher amounts in the alkaline step. The chemical composition of OP and its individual tissues (peel, flesh
and hairy flesh) was investigated and compared to the corresponding preparations of standard pumpkin (SP, Cucurbita pepo L.). The content of components (on oven-dry basis), calculated from the analysis data of the individual tissues, was estimated
for OP: 7.9 % ash, 7.6 % Klason lignin, 19.3 % pectin (as uronic acids), 34.1 % neutral carbohydrates, and 27.4 % α-cellulose
and for SP: 6.4 % ash, 4.0 % Klason lignin, 20.9% pectin (as uronic acids), 38.1% neutral carbohydrates, and 29.2 % α-cellulose,
respectively. The OP biomass showed a higher proportion of hemicelluloses. 相似文献
3.
Expression of UDP-glucose dehydrogenase reduces cell-wall polysaccharide concentration and increases xylose content in alfalfa stems 总被引:3,自引:0,他引:3
Deborah A. Samac Lynn Litterer Glena Temple Hans-Joachim G. Jung David A. Somers 《Applied biochemistry and biotechnology》2004,116(1-3):1167-1182
The primary cell-wall matrix of most higher plants is composed of large amounts of uronic acids, primarily d-galacturonic acid residues in the back-bone of pectic polysaccharides. Uridine diphosphate (UDP)-glucose dehydrogenase is
a key enzyme in the biosynthesis of uronic acids. We produced transgenic alfalfa (Medicago sativa) plants expressing a soybean UDP-glucose dehydrogenase cDNA under the control of two promoters active in alfalfa vascular
tissues. In initial greenhouse experiments, enzyme activity in transgenic lines was up to seven-fold greater than in nontransformed
control plants; however, field-grown transgenic plants had only a maximum of 1.9-fold more activity than the control. Cell-wall
polysaccharide content was lower and Klason lignin content was higher in transgenics compared to the nontransformed control.
No significant increase in pectin or uronic acids in the polysaccharide fraction was observed in any line. Xylose increased
15% in most transgenic lines and mannose concentration decreased slightly in all lines. Because of the complexity of pectic
polysaccharides and sugar biosynthesis, it may be necessary to manipulate multiple steps in carbohydrate metabolism to alter
the pectin content of alfalfa. 相似文献
4.
Apples are the most frequently consumed fruit and about 90 % of apple production is stored. Fatty acids and lipids are important constituents of plant cells. Disturbances in the lipid composition of fruit may lead to various stress processes, resulting in some storage disorders. This work is focused on an analysis of surface lipids of different varieties of apples stored in a normal atmosphere and a modified atmosphere with ultra-low oxygen content, for 4 months and 6 months. The major fatty acids in apple surface layers are palmitic acid, stearic acid, linoleic acid, and oleic acid. During the 6-months storage period, a variety-specific decrease in the total fatty acids content and an increase in saturation degree was observed in all the varieties tested, when compared with the 4-months storage. The greatest differences in saturation degree were observed in the Golden Delicious variety, in which the highest content of unsaturated fatty acids was also found. Microbial contamination of apple surfaces increased gradually over the storage process. Higher fungi levels were found in apples stored in the regular atmosphere than in the modified atmosphere, which can be attributed to changes observed in the total lipid content and saturation degree of the surface fatty acids and also to the sensitivity of microorganisms to the oxygen content in the storage room. 相似文献
5.
《Journal of Analytical and Applied Pyrolysis》2007,80(1):16-23
A rapid method for the analysis of biomass feedstocks was established to identify the quality of the pyrolysis products likely to impact on bio-oil production. A total of 15 Lolium and Festuca grasses known to exhibit a range of Klason lignin contents were analysed by pyroprobe–GC/MS (Py–GC/MS) to determine the composition of the thermal degradation products of lignin. The identification of key marker compounds which are the derivatives of the three major lignin subunits (G, H, and S) allowed pyroprobe-GC/MS to be statistically correlated to the Klason lignin content of the biomass using the partial least-square method to produce a calibration model. Data from this multivariate modelling procedure was then applied to identify likely “key marker” ions representative of the lignin subunits from the mass spectral data. The combined total abundance of the identified key markers for the lignin subunits exhibited a linear relationship with the Klason lignin content. In addition the effect of alkali metal concentration on optimum pyrolysis characteristics was also examined. Washing of the grass samples removed approximately 70% of the metals and changed the characteristics of the thermal degradation process and products. Overall the data indicate that both the organic and inorganic specification of the biofuel impacts on the pyrolysis process and that pyroprobe–GC/MS is a suitable analytical technique to asses lignin composition. 相似文献
6.
F. A. Agblevor R. J. Evans K. D. Johnson 《Journal of Analytical and Applied Pyrolysis》1994,30(2):125-144
A rapid analytical technique has been developed to qualitatively screen and quantitatively analyze biomass feedstocks for conversion into hydrocarbon fuels and chemicals. In this rapid analytical pyrolysis approach, herbaceous biomass feedstocks stored in the open without cover for 6 to 9 months were characterized using the molecular-beam mass spectrometer (MBMS). The biomass materials were pyrolyzed at 600°C and the volatile pyrolysis products were analyzed in real time by the MBMS. The mass spectral data were further analyzed by multivariate statistical techniques (Factor Analysis). The contents of nitrogen compounds, pentosans and hexosans estimated from the pyrolysis mass-spectrometric/multivariate analysis techniques correlated well with the results obtained by conventional wet chemical methods. However, lignin correlation was very weak because of the presence of microbial degradation products of biomass (humic material) that interfered with the Klason lignin analysis.
This rapid analytical technique was used to analyze various fractions of the stored biomass feedstocks. A comparison of exposed surface biomass materials and the unexposed materials showed that the exposed fraction lost 30% (wt) of the carbohydrate component of the biomass relative to the fresh material. 相似文献
7.
Peter Westbye Tobias Köhnke Wolfgang Glasser Paul Gatenholm 《Cellulose (London, England)》2007,14(6):603-613
A crude xylan isolate obtained by prehydrolysis and mild alkaline extraction from birch wood chips (Betula pendula), and a carefully delignified xylan fraction from the same source, were examined by dynamic light scattering (DLS) and cryogenic
transmission electron microscopy (cryo-TEM) with regard to their propensity to self-assemble in water into insoluble aggregates.
The delignification involved the extraction with chloroform of a crude xylan solution in a pyridine/acetic acid/water mixture.
It resulted in a purified xylan fraction in a yield of 23% in which 75 and 90% of the lignin had been removed as indicated
by Klason and UV-determination, respectively. It was found that both xylan fractions formed agglomerates by self-assembly
in water. However, DLS and cryo-TEM indicated that the aggregates were larger in size (90 vs. 40 nm) and greater in mass when
more lignin was present. The addition of an alkaline solution of isolated lignin (obtained by steam explosion) to increasing
concentrations of a delignified xylan revealed increasing turbidity. Our conclusion is that lignin induces agglomeration of
xylan in aqueous solutions, but xylan concentration plays an active role in the aggregation phenomena. An agglomeration mechanism
for lignin rich xylan fractions is proposed. 相似文献
8.
Hossein Ahari Mostafavi Seyed Mahyar Mirmajlessi Seyed Mohammad Mirjalili Hadi Fathollahi Hadi Askari 《Radiation Physics and Chemistry》2012,81(6):666-671
The physico-chemical parameters (including moisture, total soluble solids, antioxidant activity, phenolic content and firmness) of cv. Red Delicious apple subjected to γ radiation were evaluated for their ability to avoid the post-harvest blue mold caused by Penicillium expansum during cold storage. Freshly harvested apples were inoculated with P. expansum. Treated fruits were irradiated at doses of 0, 300, 600, 900 and 1200 Gy and stored at 1 °C. Apples were evaluated at three month intervals. The results showed that there was a clear link between phenolic content and antioxidant activity, so that dose range of 900 Gy and higher significantly decreased phenolic content and antioxidant activity. The moisture percent of stored apples was more responsive to irradiation (at doses of 900–1200 Gy) than storage time and pathogen. Lesion diameter of pathogen-treated non-irradiated apples was significantly increased after three months. This means that storage at low temperature is not enough to avoid blue mold growth. As dose and storage time increased firmness decreased; also pathogen accelerated softening of stored apples. This study showed conclusively that low irradiation doses (300 and 600 Gy) combined with cold storage is a way to minimize apple quality losses during nine month storage period. 相似文献
9.
The possibility of the use of Klason lignin extracted from sunflower husks as a cathode-active material for primary lithium battery has been demonstrated for the first time. The chemical composition, morphological and physical features were characterized by X-ray energy dispersive spectroscopy, impedance spectroscopy, scanning electron microscopy, and infrared spectroscopy. Electrochemical behavior of Klason lignin vs. Li/Li+ was studied by galvanostatic discharge and cyclic voltammetry. The reaction mechanism in electrochemical system was discussed. The maximum specific capacity of Klason lignin amounted to 380 mAh g–1 at a current density of 25 mA g–1. 相似文献
10.
11.
Ivana Lon
arevi Biljana Pajin Jovana Petrovi Ivana Nikoli Nikola Maravi urica A
kar Drago ubari Danica Zari Borislav Mili
evi 《Molecules (Basel, Switzerland)》2021,26(19)
Resistant starch (RS) is a part of insoluble dietary fiber, and it could be recognized as a functional food ingredient in some types of confectionery products that lack dietary fiber. Unlike dark and milk chocolate, white chocolate does not contain fat-free cocoa solids rich in dietary fiber. In the present study, 5%, 10%, and 15% of white chocolate were substituted with RS in order to improve the nutritional value of enriched white chocolate. The influence of RS on rheological, textural, and thermal properties of the chocolate fat phase was firstly investigated, and then further influence on physical properties, dietary fiber content, and sensory characteristics of enriched white chocolates were investigated. The obtained results showed that enriched chocolates had increased content of total dietary fiber and reduced total fats and protein content in accordance with the added amount of RS. At the same time, RS increased viscosity and reduced the hardness and volume mean diameter in enriched chocolates in accordance with the added amount. RS improved the nutritional composition of white chocolate by increasing the content of dietary fiber. At the same time, RS did not impair the color and sensory characteristics of enriched white chocolates. 相似文献
12.
Aurita Butkeviciute Jonas Viskelis Mindaugas Liaudanskas Pranas Viskelis Ceslovas Bobinas Valdimaras Janulis 《Molecules (Basel, Switzerland)》2021,26(12)
Apples are seasonal fruits, and thus after harvesting apples of optimal picking maturity, it is important to prepare them properly for storage and to ensure proper storage conditions in order to minimize changes in the chemical composition and commercial quality of the apples. We studied the quantitative composition of triterpenic compounds in the whole apple, apple peel and apple flesh samples before placing them in the controlled atmosphere (CA) chambers, and at the end of the experiment, 8 months later. HPLC analysis showed that highest total amount of triterpenic compounds (1.99 ± 0.01 mg g−1) was found in the whole apple samples of the ‘Spartan’ cultivar stored under variant VIII (O2—20%, CO2—3%, N2—77%) conditions. Meanwhile, the highest amount of triterpenic compounds (11.66 ± 0.72 mg g−1) was determined in the apple peel samples of the ‘Auksis’ cultivar stored under variant II (O2—5%, CO2—1%, N2—94%) conditions. In the apple peel samples of the ‘Auksis’ cultivar stored under variant I (O2—21%, CO2—0.03%, N2—78.97%) conditions, the amount of individual triterpenic compounds (ursolic, oleanolic, corosolic, and betulinic acids) significantly decreased compared with amount determined before the storage. Therefore, in the apple flesh samples determined triterpenic compounds are less stable during the storage under controlled atmosphere conditions compared with triterpenic compounds determined in the whole apple and apple peel samples. 相似文献
13.
There exist large amounts of detergent fiber analysis data [neutral detergent fiber (NDF), acid detergent fiber (ADF), acid
detergent lignin (ADL)] for many different potential cellulosic ethanol feedstocks, since these techniques are widely used
for the analysis of forages. Researchers working in the area of cellulosic ethanol are interested in the structural carbohydrates
in a feedstock (principally glucan and xylan), which are typically determined by acid hydrolysis of the structural fraction
after multiple extractions of the biomass. These so-called dietary fiber analysis methods are significantly more involved
than detergent fiber analysis methods. The purpose of this study was to determine whether it is feasible to correlate detergent
fiber analysis values to glucan and xylan content determined by dietary fiber analysis methods for corn stover. In the detergent
fiber analysis literature cellulose is often estimated as the difference between ADF and ADL, while hemicellulose is often
estimated as the difference between NDF and ADF. Examination of a corn stover dataset containing both detergent fiber analysis
data and dietary fiber analysis data predicted using near infrared spectroscopy shows that correlations between structural
glucan measured using dietary fiber techniques and cellulose estimated using detergent techniques, and between structural
xylan measured using dietary fiber techniques and hemicellulose estimated using detergent techniques are high, but are driven
largely by the underlying correlation between total extractives measured by fiber analysis and NDF/ADF. That is, detergent
analysis data is correlated to dietary fiber analysis data for structural carbohydrates, but only indirectly; the main correlation
is between detergent analysis data and solvent extraction data produced during the dietary fiber analysis procedure. 相似文献
14.
为缓解我国木浆供应压力,满足混合原料制浆的实际需求,该文进行了近红外光谱快速分析混合制浆原料的研究。采集145个人为控制尾巨桉含量的尾巨桉-马占相思混合样品的近红外光谱,用常规方法测定其综纤维素、聚戊糖、Klason木质素含量。对原始光谱进行一阶导数与标准正态变换预处理后,分别运用偏最小二乘法、支持向量机法、人工神经网络法和LASSO算法建立尾巨桉、综纤维素、聚戊糖、Klason木质素含量分析模型。其中LASSO法建立的尾巨桉和综纤维素含量分析模型最优,预测均方根误差(RMSEP)分别为1.80%、0.60%;绝对偏差(AD)分别为-3.03%~3.17%、-1.03%~0.98%,模型性能可满足较精确的快速分析。偏最小二乘法建立的聚戊糖含量分析模型最优,RMSEP为0.75%,AD为-1.26%~1.33%;支持向量机法建立的Klason木质素含量分析模型最优,RMSEP为0.48%,AD为-0.82%~0.86%,两个模型性能适用于非精确性的分析。该研究为混合制浆原料的快速分析提供了可能,同时也证实了LASSO算法的适用性。 相似文献
15.
Fatma DEMR 《Turkish Journal of Chemistry》2021,45(2):282
In this study, formation and quantification of mechanochemically generated free radicals of lignin were evaluated after the extraction of lignin from olive seeds and detailed lignin characterization was performed. Lignin was extracted from crushed olive seeds as an insoluble solid using Klason method. Isolated lignin was mechanochemically grinded under cryo conditions using Cryomill and particlesizes were determined by using Zeta Sizer, structural changes were followed by XRD and FTIR-ATR; thermal stabilities were tracked by TGA and DSC. In order to enable solubility demanding studies (such as 1H‑NMR and GPC), acylation of lignin was accomplished. ESR measurements were completed to prove the nature of the radicals. Free radicals cavenging activity of olive seed lignin was determined and quantified using 2-diphenyl-1-picrylhydrazyl (DPPH) method. Number of created mechanoradicals (per gram of olive seed lignin) was calculated from the corresponding UV‑Vis spectra. Finally, morphological changes of the lignin over cryomilling was evaluated using SEM. 相似文献
16.
Jae-Jun Ahn Gui-Ran Kim Kashif Akram Kyong-Su Kim Joong-Ho Kwon 《Radiation Physics and Chemistry》2012,81(8):1215-1219
The aim of this study was to determine the effects of light conditions during 2 years of storage on the luminescence characteristics of contaminating minerals, isolated from irradiated onions of 2 different origins. The potential use of photostimulated luminescence (PSL) as a screening and thermoluminescence (TL) as a confirmatory identification method was investigated during post-irradiation periods. Nonirradiated onions had 1,612 photon counts (PCs), However, the irradiated onions had much higher PCs (45,672–469,696, positive). The PCs of the irradiated onions decreased with storage time. However, all the irradiated onions had PCs with positive values (>5,000) even after 2 years of storage except onions stored under natural light. The decline in PCs because of light conditions during storage was in the order of sunlight, artificial light, and a darkroom, respectively. Minerals extracted from the nonirradiated samples exhibited TL glow curves of low intensities with maximum peak after 300 °C. However, all irradiated samples had TL glow peaks in the temperature ranges of 185–225 °C. The TL intensity and TL ratio of the irradiated samples decreased during storage with a slight shift in the TL peak temperature towards higher temperatures. The TL characteristics were most promising for samples stored under natural light conditions, however all the irradiated onions could be identified even after 2 years of storage. 相似文献
17.
Effect of chemical modifications caused by heat treatment on mechanical properties of Grevillea robusta wood 总被引:1,自引:0,他引:1
Francis Mburu Stéphane Dumarçay Mathieu Petrissans 《Polymer Degradation and Stability》2008,93(2):401-405
Grevillea robusta, a Kenyan wood species of low durability was heat treated under inert atmosphere in laboratory conditions at temperatures between 220 and 250 °C. Modulus of rupture (MOR) and modulus of elasticity (MOE) were determined for different heat treatment conditions. MOR and MOE reduced with increase in heat treatment weight loss. MOE reduced insignificantly for weight loss less than 16% while reduction of MOR was more significant. For a fixed heat treatment temperature by varying the treatment duration, sugar content was analysed by HPLC after acidic hydrolysis and Klason lignin was determined. The amount of sugars other than glucose decreased with treatment time and was near zero after 7 h, while lignin quantity increased gradually. Wood acidity determined by titration decreased after heat treatment indicating degradation of uronic acids present in hemicelluloses. Chemical modifications of wood components were determined by CP/MAS 13C NMR analysis. Spectra indicated significant degradation of hemicelluloses. Increase of treatment duration resulted in the appearance of new signals, particularly obvious on spectra of samples treated for 15 h, attributed to carbonaceous materials involved in char formation. 相似文献
18.
Kamila Kapusniak Karolina Lubas Malwina Wojcik Justyna Rosicka-Kaczmarek Volodymyr Pavlyuk Karolina Kluziak Idalina Gonalves Joana Lopes Manuel A. Coimbra Janusz Kapusniak 《Molecules (Basel, Switzerland)》2021,26(18)
Dietary fiber can be obtained by dextrinization, which occurs while heating starch in the presence of acids. During dextrinization, depolymerization, transglycosylation, and repolymerization occur, leading to structural changes responsible for increasing resistance to starch enzymatic digestion. The conventional dextrinization time can be decreased by using microwave-assisted heating. The main objective of this study was to obtain dietary fiber from acidified potato starch using continuous and discontinuous microwave-assisted heating and to investigate the structure and physicochemical properties of the resulting dextrins. Dextrins were characterized by water solubility, dextrose equivalent, and color parameters (L* a* b*). Total dietary fiber content was measured according to the AOAC 2009.01 method. Structural and morphological changes were determined by means of SEM, XRD, DSC, and GC-MS analyses. Microwave-assisted dextrinization of potato starch led to light yellow to brownish products with increased solubility in water and diminished crystallinity and gelatinization enthalpy. Dextrinization products contained glycosidic linkages and branched residues not present in native starch, indicative of its conversion into dietary fiber. Thus, microwave-assisted heating can induce structural changes in potato starch, originating products with a high level of dietary fiber content. 相似文献
19.
Residue levels of parathion methyl on field-sprayed Granny-Smith apples were studied. The pesticide was applied according to producer recommendations. Apples received a single spraying at a rate of 40 g active ingredient/100 L. Residues were determined with a simple gas chromatographic method. Recovery of parathion methyl was 88-108%, and the limit of determination was 0.002 mg/kg. Decomposition of parathion methyl was studied in apples remaining on trees after spraying and in apples harvested and stored under ambient-temperature, refrigerated-room, and controlled-atmosphere conditions. During post harvest storage, parathion methyl degrades more slowly than on apples remaining on the trees. Best-fit curves were determined, and kinetic equations, rate constants, and half-lives were calculated. Half-lives found were 8 days for apples on trees, 45 days for apples stored at ambient conditions, 68 days for apples stored in controlled-atmosphere room, and 62 days for apples stored in a refrigerated room. Under storage conditions, levels of parathion methyl residues need a long time to become lower than the legal limit (0.2 mg/kg). 相似文献
20.
UCT-solvent pretreatment was carried out on woods (beech and akamatsu (pine)) for the enzymatic hydrolysis, in which pretreatment
the ground woods were autoclaved with a mixture of water and cyclo-hexanol (37.5% vol% cyclohexanol) having upper critical
temperature (UCT: 184°C) on the mutual solubility curve (named as UCT-solvent). Ninety-five and 92% of Klason lignin were
removed from beech and akamatsu, respectively, whereas when the woods were autoclaved with water instead of UCT-solvent, only
43 and 18% of Klason lignin was removed from them, respectively. The excellent ability of UCT-solvent for the removal of Klason
lignin is owing to that the solvent disturbs re-coupling between the degradation products. The enzymatic hydrolysis of wood
was much improved by UCT-solvent pretreatment: the hydrolytic reactivity of akamatsu was enhanced by 2.8 times comparing with
when akamatsu was pretreated with water instead of UCT-solvent. 相似文献