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71.
Ilse Bacaloglu Truong The Ky Carmen Boeriu Hans Horst Glatt Radu Bacaloglu Dieter Martin Heinz Graubaum 《Advanced Synthesis \u0026amp; Catalysis》1982,324(5):803-808
Acylation of Heterocycles with Carbonic Acid Derivatives. I. Kinetics and Mechanism of the Reaction of 2-Aminobenzimidazoles with Aryl Cyanates The second order rate constants for the reaction of 2-amino-benzimidazoles (2-ABI) with aryl cyanates forming 2-amino-benzimidazole aryl ester imide 3 have been determined in dependence on substituent effects by u. v. measurements. The results are interpreted by a six-membered cyclic transition state in which the electrophilic attack of the cyanate on the endocyclic N atom is catalyzed by an H bridge interaction of the exocyclic amino group of 2-ABI with the OCN group. 相似文献
72.
Vitamins A and E were determined by HPLC in 20 starting, milk-based powdered infant formulae from local markets. We traced the evolution of these compounds, once the packets had been opened, during 0, 30 and 70 days of storage at room temperature (≈25 °C; min. 23 °C, max. 25.5 °C). Immediately after opening the packets, vitamin A ranged from 0.55 to 0.94 mg RE/100 g (93.3–183 μg RE/100 kcal) and vitamin E from 6.58 to 27.8 mg α-TE/100 g (1.36–5.39 mg α-TE/100 kcal). All the samples had higher vitamins A and E contents than those declared on the label, vitamin A mean adequacy values: 134% ± 17, min. 98%, max. 162%, and vitamin E 185% ± 47, min. 101%, max. 286%, including values at 0, 30 and 70 days of storage. 相似文献
73.
The intracellular silver accumulation ({Ag}(in)) upon exposure to carbonate coated silver nanoparticles (AgNP, 0.5-10 μM, average diameter 29 nm) and silver nitrate (20-500 nM) was examined in the wild type and in the cell wall free mutant of the green alga Chlamydomonas reinhardtii at pH 7.5. The {Ag}(in) was measured over time up to 1 h after a wash procedure to remove silver ions (Ag(+)) and AgNP from the algal cell surface. The {Ag}(in) increased with increasing exposure time and with increasing AgNP and AgNO(3) concentrations in the exposure media, reaching steady-state concentrations between 10(-5) and 10(-3) mol L(cell)(-1). According to estimated kinetic parameters, high Ag(+) bioconcentration factors were calculated (>10(3) L L(cell)(-1)). Higher accumulation rate constants were assessed in the cell wall free mutant, indicating a protective role of the cell wall in limiting Ag(+) uptake. The bioavailability of AgNP was calculated to be low in both strains relative to Ag(+), suggesting that AgNP internalization across the cell membrane was limited. 相似文献
74.
María Del Carmen Flores‐Álvarez Erika F. Molina‐Hernández José Concepción Hernández‐Raya María Elena Sosa‐Morales 《Journal of food science》2012,77(11):C1136-C1143
Abstract: Oil that is reused multiple times for deep frying goes through changes in chemical composition and physical characteristics, affecting the quality of the fried foods. In this study, the effect of the food type (fish nuggets or French fries) on the degradation of an oil blend during the deep‐fat frying of each food at 180°C during 12 days was determined, and the characteristics of the fried products were evaluated. The degradation of oil during repeated use was relatively faster when fish nuggets were fried than when French fries were fried, as higher values of total polar compounds were obtained. Practical Application: The results are useful for producers of French fries and fish nuggets, such as restaurants or fast foods sellers, providing them with practical guidelines within the permitted values established by the regulatory authorities. The studied foods have high economic importance and are different in their composition. Under the studied conditions, the tested oil blend may be used during 4 d (4 h per day) with a daily replenishment, without discarding the oil when frying fish nuggets, and must be discarded after 8 d when French fries are processed. This suggestion allows preparing safe fried foods for consumers. 相似文献
75.
ABSTRACT: Some white wines of Chardonnay variety are aged on their lees in oak barrels over several months. Over this period, autolysis takes place and different compounds are freed in the wine, among them, nitrogen compounds. The aim of this work was to study the evolution of amines in Chardonnay wine during 180 d of maturation on lees, with and without weekly stirring. The process was carried out in new French oak barrels with 225 L capacity. From the results obtained it was found that weekly stirring mainly had an influence on histamine and tyramine concentration. The concentration of these amines at the end of the aging period was higher in the wine with weekly stirring. This treatment showed no effect on the amine concentration at the beginning of the wine aging on lees. The aging time also had an influence on the concentration of amines in the Chardonnay wine. 相似文献
76.
Concepción Vidal-Valverde M. Carmen Martin-Villa Josefa Herranz Enrique Rojas-Hidalgo 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1981,172(2):93-95
Summary The sugar content of fourteen soft drinks amply consumed in Spain has been determined by high performance liquid chromatography (HPLC). The method, fast and reliable requires a minimum of sample preparation. For the total sugar content, a comparison is made with the classical column chromatography.
Bestimmung von Kohlenhydraten in Erfrischungsgetränken durch Hochdruckflüssigkeitschromatographie
Zusammenfassung Der Zuckergehalt von vierzehn Erfrischungsgetränken, deren Verbrauch in Spanien sehr groß ist, wurde durch die Hochdruckflüssigkeitschromatographie (HPLC) festgestellt. Diese schnelle und zuverlässige Methode erfordert ein Minimum an Vorbereitungen. Für den gesamten Zuckergehalt wird ein Vergleich mit der klassischen Säulenchromatographie durchgeführt.相似文献
77.
Carmen Baudín Jonas Gurauskis Antonio Javier Sánchez-Herencia Victor M. Orera 《Journal of the American Ceramic Society》2009,92(1):152-160
Fracture features, residual stresses, and zirconia transformation are studied in indentation strength specimens of alumina-Y2 O3 -stabilized zirconia (3% mol of Y2 O3 , 3YTZP) ceramics in order to analyze the extension of the indentation damage in the bulk of the specimens. Two compositions, 5 vol% 3YTZP (A5) and 40 vol% 3YTZP (A40), have been prepared by stacking tape-casted tapes and sintering. After indentation with loads ranging from 50 to 300 N, samples were fractured in four-point bending and the fracture surfaces were characterized by scanning electron microscopy. Raman and piezospectroscopic techniques were used to determine the monoclinic zirconia fraction and the residual stresses through the fracture surfaces. In the A5 composition, the indentation damage morphology was clearly half-penny, whereas the A40 composition presented Palmqvist crack formation. Zirconia transformation was only observed in the plastically deformed zones underneath the imprints whereas there were significant residual compressive stresses outside the plastic zones due to the indentation damage. The intensity of this residual compressive field was dependent on the level of zirconia transformation due to indentation damage because zirconia transformation induced tensile stress fields superimposed on the compressive stresses. 相似文献
78.
Phenol‐enriched olive oils modify paraoxonase‐related variables: A randomized,crossover, controlled trial 下载免费PDF全文
79.
Carmen Gómez-Guillen Teresa Solas Javier Borderías Pilar Montero 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1996,202(3):221-227
This paper seeks to compare the ultrastructure of gels made from frozen muscle of giant squid (Dosidicus gigas) at various temperatures with a number of different rheological parameters, with reference to a variety of added ingredients (non-muscle proteins and hydrocolloids) and to NaCl concentration. Interesting data on gel rheological properties were found where formulae containedl-carrageenan, starch and egg white, with a low salt concentration (1.5%). This seems to be because carrageenan forms an independent network which supports the principal structure formed by the fish protein; starch is incorporated into the network and retains water; and egg white forms a supplementary network which helps to improve rheological properties. 相似文献
80.
Benjamín Escamilla‐Castillo Ren Varela‐Montellano Salvador A. Snchez‐Tovar Julio Alberto Solís‐Fuentes Carmen Durn‐de‐Bazúa 《European Journal of Lipid Science and Technology》2005,107(12):871-876
Rice bran is considered in Mexico as “waste”, useful only for feeds. As considerable amounts of oil are available in rice bran, it might be worthwhile to stabilize it and extract the edible oil before using it for feedstuffs. Precisely these oils are responsible for rice bran rapid deterioration, particularly in climatic conditions such as those prevalent in Mexico's tropical areas (high humidity and high temperature). This paper deals with the study of the effect of pH during extrusion of fresh rice bran in order to inactivate lipid‐breaking enzymes. Hydrochloric acid or calcium hydroxide, Ca(OH)2, were added at 0, 1, 5, 10% (dry basis), and moisture content of the bran samples was varied (20, 30, 40%, dry basis) in a 32 factorial design to corroborate its effect at acid and alkaline pH range. Free fatty acids (FFA) increase was the control variable. Extruded samples were stored at room temperature (between 20 and 28 °C) using a non‐extruded sample as control to assess the shelf life effects. Results indicate that in acid‐extruded samples, the increase in FFA concentration after 98 days was much less than in the unmodified‐pH or alkaline samples. The lowest FFA increase after 3 months of storage time was <10 mg FFA/g rice bran using extrusion with no water or chemicals added or using extrusion adding HCl, irrespective of the moisture content of rice bran. 相似文献