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1.
Ultrasonic study of wheat flour properties   总被引:1,自引:0,他引:1  
In this work, the wheat flour properties are investigated using ultrasound techniques. Moreover, the flour samples were also characterized by means of well established techniques such as protein content, Alveograph and Mixolab®. A set of 35 dough samples, made of wheat flours with diverse physical and quality properties, were studied. The obtained results shown that ultrasound measurements can detect changes in the dough consistency induced by proteins and also by gelatinization of the starch. Furthermore, ultrasound measurements can be related to parameters indicative of the proteolytic degradation or softening of the dough due to protease activity. Thus, ultrasound can be considered a low cost and rapid tool, complementary to conventional test, for wheat flour characterization.  相似文献   
2.
高效液相色谱法测定食品中的富马酸二甲酯   总被引:7,自引:0,他引:7  
乙酸乙酯作提取剂 ,检测波长 2 30 nm,流动相采用甲醇 -水 (4∶ 6 )的乙酸钠 -冰乙酸 -四丁基溴化铵溶液 ,高效液相色谱测定月饼、面包样品中富马酸二甲酯。优化不同性质样品的提取条件及测定的流动相。不同样品的富马酸二甲酯的回收率在 93%— 95 %之间 ,在 0— 2 5 0 .0 μg/ m L校准曲线的回归方程为 y=0 .0 0 4 5 2 x 0 .0 0 5 2 3,相关系数 r=0 .9995 ,相对标准偏差小于 1.6 %。本法简单、快速、准确 ,可用于各种食品中的富马酸二甲酯的日常检测。  相似文献   
3.
A new NIR method based on multivariate calibration for determination of ethanol in industrially packed wholemeal bread was developed and validated. GC-FID was used as reference method for the determination of actual ethanol concentration of different samples of wholemeal bread with proper content of added ethanol, ranging from 0 to 3.5% (w/w). Stepwise discriminant analysis was carried out on the NIR dataset, in order to reduce the number of original variables by selecting those that were able to discriminate between the samples of different ethanol concentrations. With the so selected variables a multivariate calibration model was then obtained by multiple linear regression. The prediction power of the linear model was optimized by a new “leave one out” method, so that the number of original variables resulted further reduced.  相似文献   
4.
The consumer quality of baked products is closely related with dough structure properties. These are developed during dough fermentation and finalized during its baking. In this study, magnetic resonance microscopy (MRM) was employed in a study of dough fermentation and baking. A small hot air oven was installed inside a 2.35-T horizontal bore superconducting magnet. Four different samples of commercial bread mixes for home baking were used to prepare small samples of dough that were inserted in the oven and allowed to rise at 33°C for 112 min; this was followed by baking at 180°C for 49 min. The entire process was followed by dynamic T1-weighted 3D magnetic resonance imaging with 7 min of temporal resolution and 0.23×0.23×1.5 mm3 of spatial resolution. Acquired images were analyzed to determine time courses of dough pore distribution, dough volume and bread crust thickness. Image analysis showed that both the number of dough pores and the normalized dough volume increased in a sigmoid-like fashion during fermentation and decreased during baking due to the bread crust formation. The presented magnetic resonance method was found to be efficient in analysis of dough structure properties and in discrimination between different dough types.  相似文献   
5.
Two-dimensional (2D)-SE, 2D-GE and tri-dimensional (3D)-GE two-point T(1)-weighted MRI methods were evaluated in this study in order to maximize the accuracy of temperature mapping of bread dough during thermal processing. Uncertainties were propagated throughout each protocol of measurement, and comparisons demonstrated that all the methods with comparable acquisition times minimized the temperature uncertainty to similar extent. The experimental uncertainties obtained with low-field MRI were also compared to the theoretical estimations. Some discrepancies were reported between experimental and theoretical values of uncertainties of temperature; however, experimental and theoretical trends with varying parameters agreed to a large extent for both SE and GE methods. The 2D-SE method was chosen for further applications on prefermented dough because of its lower sensitivity to susceptibility differences in porous media. It was applied for temperature mapping in prefermented dough during chilling prior to freezing and compared locally to optical fiber measurements.  相似文献   
6.
A sensitive and accurate method employing a single stage high resolution mass spectrometer equipped with a high-energy collision-dissociation cell (HCD) for the simultaneous determination of deoxynivalenol (DON), T-2 toxin (T-2) and HT-2 toxin (HT-2) in a processed bread model food has been developed. Two sample pre-treatment routes for the extraction of these mycotoxins were investigated, based on Mycosep® column clean up or QuEChERS-like procedure, respectively. The former approach suffered less from matrix effects and allowed to achieve in bread samples LODs of 7, 12 and 17 ng/g for T-2, HT-2 and DON, respectively, with 0.5 ppm mass accuracy. Two acquisition modes, full scan MS and all ion fragmentation, exploiting the fragmentation features offered by an HCD chamber and integrated within the Orbitrap analyser, were compared for quantitative purposes. The method was applied to investigate the degradation of these mycotoxins during bread processing using a bread model food. Most T-2 hydrolyzed to HT-2 during dough preparation, and about 20–30% of HT-2 and DON was degraded during bread baking.  相似文献   
7.
Magnetic resonance imaging has proven its potential application in bread dough and gas cell monitoring studies, and dynamic processes such as dough proving and baking can be monitored. However, undesirable magnetic susceptibility effects often affect quantification studies, especially at high fields. A new low-field method is presented based on local assessment of porosity in spin-echo imaging, local characterization of signal loss in gradient-echo imaging and prediction of relaxation times by simulation to estimate bubble radii in bread dough during proving. Maps of radii showed different regions of dough constituting networks which evolved during proving. Mean radius and bubble distribution were assessed during proving.  相似文献   
8.
Analytical methods currently employed for determination of acrylamide (AA) in two carbohydrate-rich food samples, crispbread and butter cookies, obtained commercially, and native and spiked bread extract samples have been evaluated in a collaborative study. The objective of the study was to obtain information about the performance of the participating laboratories when analysing samples with an AA content close to the limit of quantification (LOQ) and at a higher AA level, and to investigate the influence of sample-preparation procedures on the results of the analysis. For this purpose an aqueous native extract of white bread crumb, a fortified extract, and AA standard solutions, the analyte content of which were not disclosed to the participants, were included in the study. A total of 62 laboratories, applying seven different measurement techniques and a broad spectrum of analyte extraction and sample-preparation procedures reported their analytical results. Because the measurement data were not normally distributed, they were evaluated by application of robust statistics. The relative performance of the laboratories was highlighted by calculation of z-scores. For the crispbread sample, especially, a large percentage of the calculated z-scores were outside the satisfactory range. From their distribution it became obvious that one of the analytical techniques might be biased, if not applied correctly. Consequently, the impact of the applied methods was examined in more detail. Information about the analytical technique, extraction solvent, quantity weighed, calibration method, clean-up, and the experience of the participating laboratories were extracted from the analytical protocols and transcribed into a data matrix which was evaluated by multifactor analysis of variance. The applied measurement technique seems to have a statistically significant influence on the analytical results.  相似文献   
9.
周小华  王东  郑声申 《应用化学》2009,26(9):1088-1089
采用磷酸二异辛酯(P204)/正辛醇反胶束液从面包酵母粗提液中萃取还原型谷胱甘肽(GSH),研究了各种因素对萃取率的影响以及水相pH值和P204浓度与GSH萃取率关系的数学模型。正交实验确定,GSH的最佳萃取条件是水相pH值2.0,K+浓度0.1 mol•L-1,萃取时间15 min,P204浓度0.16 mol•L-1,GSH单次的萃取率为33.1%,2次萃取率达到49.7%。  相似文献   
10.
通过低价钛引起的交叉羰基的偶联合成了二茂铁基二芳基乙烯衍生物,原料廉价易得,合成步骤简便,产率达74%。  相似文献   
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