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131.
Rivas B Torre P Domínguez JM Converti A Parajó JC 《Journal of agricultural and food chemistry》2006,54(12):4430-4435
Hydrolysates obtained by autohydrolysis-posthydrolysis of corncobs were detoxified with charcoal, concentrated, supplemented with nutrients, and fermented with Debaryomyces hansenii. After biomass removal, the fermented media contained 0.1137 kg of nonvolatile components (NVC)/kg of liquor, which corresponded mainly to xylitol (0.6249 kg/kg of NVC) but also to minor amounts of inorganic components (measured as ashes), proteins, nonfermented sugars (xylose and arabinose), uronic acids, arabitol, and other nonvolatile components (ONVC). The media were subjected to further processing (sequential stages of adsorption, concentration, ethanol precipitation, concentration, and crystallization) to obtain food-grade xylitol. Adsorption experiments were carried out at various solid-to-liquor ratios. Under selected conditions (1 kg of charcoal/15 kg of liquors), the xylitol content increased to 0.6873 kg/kg of NVC, and almost total decoloration was achieved. The resulting liquor was concentrated by evaporation to increase its NVC content to 0.4032 kg/kg of liquor (corresponding to a xylitol concentration of 0.280 kg/kg of liquor), and ethanol was added to precipitate a part of the NVC (mainly proteins, but also uronic acids, ashes, and other nonvolatile compounds). Refined liquors (containing 0.7303 kg of xylitol/kg of NVC) were concentrated again, and ethanol was added (to reach 40-60% volume of the stream) to allow crystallization at -10 or -5 degrees C. Under selected conditions, 43.7% of xylitol contained in the initial fermentation broth was recovered in well-formed, homogeneous crystals, in which xylitol accounted for 98.9% of the total oven-dry weight. Material balances are presented for the whole processing scheme considered in this work. 相似文献
132.
Faleiro L Miguel G Gomes S Costa L Venâncio F Teixeira A Figueiredo AC Barroso JG Pedro LG 《Journal of agricultural and food chemistry》2005,53(21):8162-8168
Antilisterial activities of Thymbra capitata and Origanum vulgare essential oils were tested against 41 strains of Listeria monocytogenes. The oil of T. capitata was mainly constituted by one component, carvacrol (79%), whereas for O. vulgare three components constituted 70% of the oil, namely, thymol (33%), gamma-terpinene (26%), and p-cymene (11%). T. capitata essential oil had a significantly higher antilisterial activity in comparison to O. vulgare oil and chloramphenicol. No significant differences in L. monocytogenes susceptibilities to the essential oils tested were registered. The minimum inhibitory concentration values of T. capitata essential oil and of carvacrol were quite similar, ranging between 0.05 and 0.2 microL/mL. Antioxidant activity was also tested, the essential oil of T. capitata showing significantly higher antioxidant activity than that of O. vulgare. Use of T. capitata and O. vulgare essential oils can constitute a powerful tool in the control of L. monocytogenes in food and other industries. 相似文献
133.
Morales F Cartelat A Alvarez-Fernández A Moya I Cerovic ZG 《Journal of agricultural and food chemistry》2005,53(25):9668-9678
Synchrotron radiation and the time-correlated single-photon counting technique were used to investigate the spectral and time-resolved characteristics of blue-green fluorescence (BGF) of artichoke leaves. Leaves emitted BGF under ultraviolet (UV) excitation; the abaxial side was much more fluorescent than the adaxial side, and in both cases, the youngest leaves were much more fluorescent than the oldest ones. The BGF of artichoke leaves was dominated by the presence of hydroxycinnamic acids. A decrease in the percentage of BGF attributable to the very short kinetic component (from 42 to 20%), in the shape of the BGF excitation spectra, and chlorogenic acid concentrations indicate that there is a loss of hydroxycinnamic acid with leaf age. Studies on excitation, emission, and synchronized fluorescence spectra of leaves and trichomes and chlorogenic acid contents indicate that chlorogenic acid is one of the main blue-green fluorophores in artichoke leaves. Results of the present study indicate that 20-42% (i.e., the very short kinetic component) of the overall BGF is emitted by chlorogenic acid. Time-resolved BGF measurements could be a means to extract information on chlorogenic acid fluorescence from the overall leaf BGF. 相似文献
134.
Nematicides are widely used to control plant-parasitic nematodes in intensive export banana (Musa spp.) cropping systems. Data show that the concentration of fosthiazate in banana fruits varies from zero to 0.035 g kg-1, under the maximal residue limit (MRL=0.05 mg kg-1). The fosthiazate concentration in fruit is described by a Gaussian envelope curve function of the interval between pesticide application and fruit harvest (preharvest interval). The heterogeneity of phenological stages in a banana population increases over time, and thus the preharvest interval of fruits harvested after a pesticide application varies over time. A phenological model was used to simulate the long-term harvest dynamics of banana at field scale. Simulations show that the mean fosthiazate concentration in fruits varies according to nematicide application program, climate (temperature), and planting date of the banana field. This method is used to assess the percentage of harvested bunches that exceed a residue threshold and to help farmers minimize fosthiazate residues in bananas. 相似文献
135.
Haruenkit R Poovarodom S Leontowicz H Leontowicz M Sajewicz M Kowalska T Delgado-Licon E Rocha-Guzmán NE Gallegos-Infante JA Trakhtenberg S Gorinstein S 《Journal of agricultural and food chemistry》2007,55(14):5842-5849
In vitro and in vivo studies of the health and nutritional properties of durian (Durio zibethinus Murr.) were compared with snake fruit (Salacca edulis Reinw.) and mangosteen (Garcinia mangostana). Dietary fibers, minerals, and trace metals were comparable. Total polyphenols (mg of GAE/100 g of FW) and flavonoids (85.1+/-6.1) were significantly higher (p<0.05) than in snake fruit (217.1+/-13.2 (mg of CE/100 g of FW)), durian (309.7+/-19.3 and 61.2+/-4.9), and mangosteen (190.3+/-12.1 and 54.1+/-3.8). Antioxidant activity (microM TE/100 g of FW) of durian measured by DPPH and ABTS assays (228.2+/-13.4 and 2016.3+/-81.1) was significantly higher (p<0.05) than in snake fruit (110.4+/-7.9 and 1507.5+/-70.1) and mangosteen (79.1+/-5.9 and 1268.6+/-62.3). HPLC/DAD analysis of durian (microg/100 g of FW) showed that quercetin (1214.23+/-116.7) was present at levels three times that of caffeic acid, and twice as high as p-coumaric and cinnamic acids. The correlation coefficients between the bioactive compounds of fruits and their antioxidant activities were high (R2=0.99). Male Wistar rats (25) were divided into five dietary groups: the control group was fed the basal diet (BD); in addition to BD, the cholesterol (Chol) group was supplemented with 1% of Chol; the diets of the Chol/Durian, Chol/Snake, and Chol/Mangosteen groups were supplemanted with 5% of these fruits, respectively. It was found that diets supplemented with durian, and to a lesser degree with snake fruit and mangosteen, significantly hindered the rise in plasma lipids and the decrease in antioxidant activity. The nutritional values were comparably high. In conclusion, it could be suggested that inclusion of studied tropical fruits, especially durian, in known disease-preventing diets could be beneficial. 相似文献
136.
The time evolution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH*) concentration in four solvents (methanol, ethanol, propanol, and acetonitrile) during its reduction by three flavanones containing an isolated p-catechol group (taxifolin, eriodyctiol, and fustin) as well as the time evolution of the mass spectra of the reaction mixture has been determined by spectrophotometry and liquid mass spectrometry, respectively. In alcoholic solvents the reduction curves consisted of an initial short but fast kinetics step followed by a longer slow kinetics step; in contrast, in acetonitrile the reduction curves completely lacked the slow kinetics step. From the results, a kinetic model for the reaction of reduction of the DPPH* by the isolated p-catechol group in flavanone type structures is proposed. According to this model, the p-catechol group rapidly transfers two hydrogen atoms to DPPH*, through a fast rate constant k1, yielding the corresponding o-quinone. Then, the intermediate o-quinone forms an adduct with the alcoholic solvent, through a slow rate constant k2, and regenerates the p-catechol group. The regenerated p-catechol group reduces additional DPPH* through a fast rate constant k3, yielding the corresponding o-quinone, which can form a new adduct with the solvent to regenerate the p-catechol group, and so on. From the kinetics model, two explicit kinetics equations have been derived that fit very well the experimental data points acquired from all assayed compounds in all of the experiments carried out, thus allowing an accurate determination of the corresponding rate and stoichiometric constants. 相似文献
137.
Astruc T Marinova P Labas R Gatellier P Santé-Lhoutellier V 《Journal of agricultural and food chemistry》2007,55(23):9554-9558
In meat, no detailed studies on the intracellular distribution of oxidized proteins during oxidative stress have been performed, to our knowledge. Therefore, we used fluorescence microscopy to detect and locate protein carbonyls, oxidation products of basic amino acids, generated in bovine M. Rectus abdominis during either exposition to a chemical free radical generating system, or refrigerated storage, or cooking. The technique consisted of an immunohistochemical detection of carbonyls by reaction with the specific probe DNPH (2,4-dinitrophenylhydrazine) followed by the sequential addition of a first antibody against DNPH-carbonylated proteins and a CY3-labeled secondary antibody. The fluorescence of the CY3 probe increased regularly with level of free radical generating system and storage time. Moreover, an important heterogeneity of carbonyl distribution was observed, with a higher oxidation level at the periphery than inside the muscle cells. Cooking induced fluorescence increase only at the periphery of cells. Specific coloration of collagen by Sirius red showed that collagen was not involved in fluorescence. We can deduce that accumulation of oxidized proteins observed in the cell periphery was linked to membrane protein oxidation and not to connective tissue oxidation. Biochemical assays were performed in parallel on membrane and myofibrillar proteins to provide complementary quantitative data on level of oxidized proteins. 相似文献
138.
Rezzi S Giani I Héberger K Axelson DE Moretti VM Reniero F Guillou C 《Journal of agricultural and food chemistry》2007,55(24):9963-9968
The combination of (1)H NMR fingerprinting of lipids from gilthead sea bream (Sparus aurata) with nonsupervised and supervised multivariate analysis was applied to differentiate wild and farmed fish and to classify farmed specimen according to their areas of production belonging to the Mediterranean basin. Principal component analysis (PCA) applied on processed (1)H NMR profiles made a clear distinction between wild and farmed samples. Linear discriminant analysis (LDA) allowed classification of samples according to the geographic origin, as well as for the wild and farmed status using both PCA scores and NMR data as variables. Variable selection for LDA was achieved with forward selection (stepwise) with a predefined 5% error level. The methods allowed the classification of 100% of the samples according to their wild and farmed status and 85-97% to geographic origin. Probabilistic neural network (PNN) analyses provided complementary means for the successful discrimination among classes investigated. 相似文献
139.
Background, Aim and Scope The distribution of sediments in estuarine beaches is controlled by the interactions between sediment supply, hydrodynamic
processes and human intervention. The main purpose of this study is to characterize the sediments of Tagus estuarine beaches
in order to understand their origin and to contribute to a better knowledge of the Tagus estuary sediment budget.
Methods Surface sediment samples were collected across beach profiles and sand grain size analysis was performed by dry sieving. Grain
size statistics for the median (d50) and standard deviation (SDM) were obtained using the Moment method. This study was complemented by a qualitative evaluation
of the sediment composition. Cross-shore topographic surveys were conducted for selected sampling sites.
Results Tagus estuarine beach sediments are mainly composed of quartz sand particles which are fine-grained and well sorted near the
mouth of the estuary and medium to coarse-grained and moderately sorted in the inner domain. Compositional results show evidence
of active anthropogenic sediment sources, especially in the coarser fractions.
Discussion The analysis of the textural and compositional characteristics of beach sediments in the inner estuarine domain is compatible
with local sedimentary sources, while a marine signature is present at the mouth and inlet channel sediments. In the inner
domain, differences in the sedimentary processes are represented by the textural characteristics of the sediments, such as
the sorting degree and the gravel content. Sediment characteristics also reflect human intervention in the system, with the
introduction of anthropogenic and allochthonous particles and the mixture of sediments from different sources.
Conclusions The sediments of the inner Tagus estuarine beaches are derived from local Plio-Pleistocene outcrops while inlet and outer
estuary beaches reveal a dominant marine source. Beach textural variability observed in the inner domain is not related to
wave forcing gradients, but mainly to variations in the sedimentary processes along the estuarine margins and to human intervention.
Results show that the Tagus estuarine beaches depended, almost exclusively, on sediment input from local sources until the
last century. With increasing human occupation, sediment transfers became dominated by anthropogenically related activities
mainly connected with the occupation of estuarine margins and dredging.
Recommendations and Perspectives Further studies should extend the present level of knowledge in what concerns sand transport patterns through additional compositional
and geochemical analysis, and the development of new techniques in order to allow the quantitative evaluation of the impact
of human activities on the sediment budget. 相似文献
140.
该文就沙枣树胶对红葡萄树提取液抗氧性的保护作用及其变化进行了初步研究,结果表明红葡萄树提取液具有极强的抗羟自由基(H0·)能力,而抗超氧阴离子自由基(O-2·)的能力较弱,即在空气中易氧化、抗氧活性迅速降低、消失;当加入沙枣树胶初期,其抗氧性能迅速降低,3d后开始上升,15d后其对超氧阴离子自由基清除率达到30%,60d后对羟自由基清除率达到68%,其后,一直保持稳定.在沙枣树胶的多糖活性成分的作用下,红葡萄树胶的抗氧活性显著增强,稳定性提高.研究结果初步表明,沙枣树胶对红葡萄树提取液的抗氧活性具有显著的保护作用. 相似文献