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951.
The aim of this study was to evaluate the usefulness of visible (VIS), near-infrared reflectance (NIR) and mid-infrared (MIR)
spectroscopy combined with pattern recognition methods as tools to differentiate grape juice samples from commercial Australian
Chardonnay (n = 121) and Riesling (n = 91) varieties. Principal component analysis (PCA), partial least squares discriminant analysis and linear discriminant
analysis (LDA) were applied to classified grape juice samples according to variety based on both NIR and MIR spectra using
full cross-validation (leave-one-out) as a validation method. Overall, LDA models correctly classify 86% and 80% of the grape
juice samples according to variety using MIR and VIS-NIR, respectively. The results from this study demonstrated that spectral
differences exist between the juice samples from different varietal origins and confirmed that the infrared (IR) spectrum
contains information able to discriminate among samples. Furthermore, analysis and interpretation of the eigenvectors from
the PCA models developed verified that the IR spectrum of the grape juice has enough information to allow the prediction of
the variety. These results also suggested that IR spectroscopy coupled with pattern recognition methods holds the necessary
information for a successful classification of juice samples of different varieties. 相似文献
952.
Franco Van de Velde María E. Pirovani María S. Cámara Daniel R. Güemes Cecilia M. del H. Bernardi 《Food Analytical Methods》2012,5(5):1097-1104
Vitamin C or total ascorbic acid (TAA) in fruits can be assumed as ascorbic acid (AA) plus dehydroascorbic acid (DHA) content. The aim of this work was to optimize and validate, using experimental designs, a new high-performance liquid chromatographic method for vitamin C determination in strawberries. The mobile phase (MP) consisted of a 0.03 M sodium acetate/acetic acid buffer, 5% methanol. For optimization, a Box–Behnken design was used (three factors at three levels: (a) pH of MP, 3.8–5.8; (b) wavelength, 240–270 nm; and (c) flow rate, 0.5–1.2 ml min−1). Responses were: AA and TAA areas, peak widths, and retention times. A global optimization was performed using the Derringer desirability function, and a value of 0.84 was reached for the combination of design factors: A = 5.8, B = 251 nm, and C = 1.15 ml min−1. Method validation, using AA standard solutions, included: linearity study, limits of detection and quantification, and calibration and analytical sensitivity quantifications. Precision and accuracy were studied in strawberry extracts. The coefficients of variation (percent) were: AA, 1.5%; TAA, 1.8%, and DHA, 4.9%. Accuracy was evaluated with AA standard spiked in 30–150% range of the expected amount of analyte in real samples. The joint confidence elliptical region test and t test were employed for the study of the difference between recoveries (percent) and the ideal 100%. The robustness was analyzed using a fractional factorial design (34−2), and an AA recovery study after slight changes in operative variables was performed. The results indicate that the optimized method was linear, sensible, precise, accurate, and robust. 相似文献
953.
Agnès Princivalle Guilhem MartinCéline Viazzi Christian GuizardNicolas Grunbaum Laurent Dessemond 《Journal of power sources》2011,196(22):9238-9245
Ceramic powders of BaCe0.9Y0.1O2.95 (BCY10) have been prepared by the sol-gel method. Barium and yttrium acetate and cerium nitrate were used as ceramic precursors in a water solution. The reaction process studied by DTA-TG and XRD showed that calcination of the precursor powder at T ≥ 1000 °C produces a single perovskite phase. The densification behaviour of green compacts studied by constant heating rate dilatometry revealed that the shrinkage rate was maximal at 1430 °C. Sintered densities higher than 95% of the theoretical one were thus obtained below 1500 °C. The bulk and additional blocking effects were characterized by impedance spectroscopy in wet atmosphere between 150 and 600 °C. A proton conduction behaviour was clearly identified. The blocking effect can be related to a space-charge depletion layer of protons in the vicinity of grain boundaries. 相似文献
954.
An econometric study of the Portuguese residential electricity consumption is presented, with a focus on the influence of dwelling characteristics on consumption. The relationship between the dwelling and household characteristics on per capita residential electricity consumption is estimated at two different scales, involving two distinct databases: the first includes data at the municipality level for 2001, the second is the most recent Portuguese consumer expenditure survey that was collected in 2005 and 2006. The results of the analysis at both scales are consistent and indicate that household and dwelling characteristics have a significant influence on residential electricity consumption. Our results show that in Portugal the direct effect of income on electricity consumption is low and becomes smaller when more relevant control variables are included in the analysis. Future demand of electricity in Portugal will be significantly influenced by trends in socioeconomic factors as well as changes in the building stock. These trends should be taken in consideration in the formulation of policy measures to reduce electricity consumption. 相似文献
955.
Shuxun Shao Xiubo Mi Laurent Ouerdane Ryszard Lobinski Juan Francisco García-Reyes Antonio Molina-Díaz Andrea Vass Mihály Dernovics 《Food Analytical Methods》2014,7(5):1147-1157
Orthogonal liquid chromatographic (ion exchange, reversed phase, and ion pairing) and mass spectrometric [electrospray ionization (ESI)-TOF-MS, ESI-Orbitrap MS, and inductively coupled plasma mass spectrometry (ICP-MS)] methods were addressed to identify and quantify selenium species from a naturally Se-enriched green bean (Phaseolus vulgaris vulgaris) sample after proteolytic digestion. While selenomethionine (10.1 mg/kg as Se) and selenate (9.5 mg/kg as Se) could be quantified in a straightforward way by anion exchange LC-ICP-MS technique, a multistep purification protocol was required to identify Se-methylselenocysteine and γ-glutamyl-Se-methylselenocysteine in an unambiguous way prior to quantification by using either in-source fragmentation (LC-ESI-TOF-MS) or collision-induced dissociation (LC-ESI-Orbitrap MS). Finally, Se-methylselenocysteine (2.6 mg/kg as Se) and γ-glutamyl-Se-methylselenocysteine (1.2 mg/kg as Se) could contribute to the overall selenium recovery of 72 %. This sample is the first of the Faboideae subfamily and Phaseolus ssp. to be speciated to such an extent for selenium including γ-glutamyl-Se-methylselenocysteine, a highly potential selenium species, which makes this bean material an ideal candidate for functional food purposes. 相似文献
956.
Daniel Cozzolino Marcel Labandera 《Journal of the science of food and agriculture》2002,82(4):380-384
Near‐infrared reflectance spectroscopy (NIRS) was used to predict the dry matter (DM) and crude protein (CP) contents of untreated forage samples. Four hundred forage samples were analysed in reflectance mode. Two mathematical treatments based on the order of derivative of log(1/R), the gap in data points and the numbers of data points used in the first and second smoothings were applied. Predictive equations were developed using modified partial least squares (MPLS) with internal cross‐validation. The coefficient of determination of calibration and the standard error of cross‐validation (SECV, in parentheses) for DM were 0.92 (12.4), 0.92 (12.6) and 0.93 (11.7) for the two treatments and log(1/R) respectively on a g kg?1 fresh weight basis. For CP the NIRS calibration statistics yielded and SECV (in parentheses) values of 0.85 (19.8), 0.85 (19.5) and 0.87 (18.1) for the two treatments and log(1/R) respectively on a g kg?1 fresh weight basis. It was concluded that NIRS is a suitable method to predict the dry matter and crude protein contents of fresh forage without sample preparation. © 2002 Society of Chemical Industry 相似文献
957.
Daniel Alberto Sánchez Gabriela Marta Tonetto María Luján Ferreira 《Journal of the American Oil Chemists' Society》2014,91(2):261-270
New avenues to add value to glycerol are currently being explored. One of them is the synthesis of structured lipids through glycerol esterification. In this work we have analyzed the recovery and purification of dicaprin obtained by esterification of glycerol with capric acid (C) in heptane, mediated by Lipozyme RM IM. This is an intermediate step to obtain lipids MLM. In the first stage, the diglyceride synthesis MGM (being G a central HC–OH) was carried out. When M = C, the diglyceride is CGC. Recovery of the diglyceride CGC is required to carry out the esterification of the sn-2 position with palmitic acid (P), thus obtaining the triglyceride CPC. Different solvents were evaluated using Ecofac 1.0 (a molecular design software solvent) through a theoretical approach to explore the best solvents for the acylglycerides separation. Then, the performance of the selected solvents to separate dicaprin from mono and tricaprin was experimentally studied in a liquid–liquid extraction process. Previously, the remaining fatty acid had been neutralized. With liquid–liquid extraction in three simple steps, using ethanol/water, 94 % of the dicaprin obtained by enzymatic esterification was recovered with a purity of 89 % (wt%). It was also possible to obtain dicaprin with a purity of 97 % but with a yield of 56 %. 相似文献
958.
Simon Laurent 《精细化工原料及中间体》2014,(4)
正本发明涉及到含有载体的催化剂,载体包括至少一种粘结剂和至少一种沸石以及至少一系列通道,由含12个氧原子限定的通道是开放的,所说催化剂包含磷,至少一种C1~C4二烷基丁二酸酯,醋酸和氢化-脱氢功能团,官能团含有至少一个族ⅥB元素和至少一个族Ⅷ元素。 相似文献
959.
Jonathan A. Zerkowski Alberto Nuñez Daniel K. Y. Solaiman 《Journal of the American Oil Chemists' Society》2008,85(3):277-284
Using ester-forming reactions such as carbodiimide coupling and a modified Yamaguchi symmetrical anhydride method, a variety
of estolides based on 17-hydroxy oleic and 17-hydroxy stearic acid have been prepared. These hydroxy fatty acids are produced
in good yields from hydrolysis of sophorolipids, which are in turn derived from fermentation of fats and oils. Since the estolides
are formed one unit, or ester bond, at a time, their length and sequence can be precisely controlled. The key to this control
is the use of protecting groups at either the carboxylic or hydroxy end of the starting hydroxy fatty acids. Two mono-protected
dimers, for example, when combined in a fragment-condensation approach, give a tetramer with no “contamination” from estolides
of other lengths. This methodology opens the way to functionalized estolides, and several variants were prepared: hybrid estolides,
containing non-fatty acid moieties such as amino acids; polymerizable estolides, containing a norbornene unit; and non-linear
estolides that extend from a branched core such as glycerol or pentaerythritol. With the benzoyl chloride-mediated symmetrical
anhydride method, yields for individual coupling steps ranged from 75 to 93%.
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the US Department of Agriculture. 相似文献
960.
ABSTRACT: One of the major growth segments in the food retail industry is fresh and minimally processed fruits and vegetables. This new market trend has thus increased the demands to the food industry for seeking new strategies to increase storability and shelf life and to enhance microbial safety of fresh produce. The technology of edible coatings has been considered as one of the potential approaches for meeting this demand. Edible coatings from renewable sources, including lipids, polysaccharides, and proteins, can function as barriers to water vapor, gases, and other solutes and also as carriers of many functional ingredients, such as antimicrobial and antioxidant agents, thus enhancing quality and extending shelf life of fresh and minimally processed fruits and vegetables. This review discusses the rationale of using edible coatings on fresh and minimally processed produce, the challenges in developing effective coatings that meet the specific criteria of fruits and vegetables, the recent advances in the development of coating technology, the analytical techniques for measuring some important coating functionalities, and future research needs for supporting a broad range of commercial applications. 相似文献