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Acta Alimentaria
Authors:
C. Cano-Molina
,
A. López-Fernández
,
N. Díaz-González
,
R. González-Barrio
,
N. Baenas
,
M.J. Periago
, and
F.J. García-Alonso

, leaving room for further biosynthesis of bioactive compounds. Various strategies have been developed to increase the concentration of bioactive compounds during post-harvest storage. Among them, artificial lighting treatments using ultraviolet light (UV

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Abstract  

Thermal, chemical and rheological properties of ultraviolet aged asphalt binder were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) and dynamic shear rheometer (DSR), respectively. Asphalt binder samples were made with different film thickness (50, 100, 200 and 500 μm) and suffered different ageing time (0, 48, 96 and 144 h), at a certain UV radiant intensity of 20 w m–2 in a self-made accelerated ageing oven. The results indicate that the UV light ageing would lead to the improvement of thermal behavior and the growth of the glass transition temperature of asphalt binder. This type of ageing can be also reflected from the FTIR spectra in terms of the characteristic peaks of the carbonyl groups and sulphoxides. The UV light ageing can change some rheological parameters of asphalt binder, such as complex modulus and phase angle. The ageing degrees of asphalt binder by this type of ageing test are mainly related to the ageing time and film thickness of the sample.

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A microwave-assisted ultraviolet sterilization system was developed to study the synergistic effect in the sterilization of milk. Electrodeless lamps emitting ultraviolet radiation inside the microwave chamber gave a synergistic effect without challenging food safety standards. This study compared the results of both microwave and microwave assisted ultraviolet sterilizations of milk in terms of various microbial tests and physicochemical properties. The microwave-assisted ultraviolet system was found to be more effective compared to microwave alone. A significant difference (P<0.05) was observed for total plate count and methylene blue reduction test between microwave and microwave assisted ultraviolet treatment from 5 to 15 secs. Microwave-assisted ultraviolet treatment decreased the microbial count exponentially and showed <1 log (CFU ml–1) after ten seconds of treatment. During the treatment period, no significant difference was observed in the physicochemical properties of milk.

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ultraviolet illumination (UV) [ 2 , 3 , 15 – 17 , 23 – 25 ], and UV intensity [ 3 , 26 ]. Various AOP combinations often result in synergistic effects that significantly reduce the required reaction time [ 5 , 6 , 8 – 10 ]. In recent years

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Abstract  

A small ultraviolet-visible absorption spectrometer which uses fibre optic coupled immersion probes has been incorporated into a laboratory scale reaction calorimeter. The combined instrument has been tried out using the hydrolysis of acetic anhydride as a test reaction. With the calorimeter operating in the isoperibolic mode good agreement is found for the pseudo-first order reaction rate constant as determined from spectroscopic and calorimetric measurements. Experiments have been made in order to follow the reaction indirectly using optical pH measurements with acid-base indicators. The possibility of determining the temperature dependence of the rate constant in a single experiment has also been investigated.

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Summary

High-performance liquid chromatography has been used for measurement of the concentrations of total cysteine and cysteinylglycine in human urine. The method involved conversion of disulfides to their reduced counterparts by use of tris(2-carboxyethyl)phosphine hydrochloride, derivatization with 1-benzyl-2-chloropyridinium bromide, and ion-pairing reversed-phase high-performance liquid chromatographic separation with ultraviolet detection at 315 nm. The linearity of the method was validated in the ranges 50–300 and 5–50 µmol L−1 urine for cysteine and cysteinylglycine, respectively; regression coefficients were better than 0.999. The detection and quantitation limits were 0.2 and 0.5 µmol L−1, respectively, for both analytes. Intra-assay and inter-assay imprecision were below 6.0%, and accuracy was 98.95–100.80%. The method was applied to urine samples donated by apparently healthy volunteers.

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25-hydroxycholecalciferol, vitamin D and ultraviolet light as determinants of circulating 25-hydroxyvitamin D. Lancet, 1977, June 25, 1341. Holick, M. F., MacLaughlin, J. A., Clark, M. B. és mtsai

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Using thermal volatilization analysis with differential condensation of volatile products, with film samples on flat-bottomed silica glass reaction tubes to permit measurements of UV spectra of partly degraded polymer, the thermal stability, the types of volatile products and the development of conjugation in the involatile residue have been compared for poly(vinyl chloride), polychloroprene, poly(vinyl acetate) and vinyl acetate/ethylene copolymers, poly(vinyl formate) and poly(vinyl alcohol). All undergo a side-group elimination reaction at lower temperatures, and polyene breakdown occurs in all the samples between 400 and 500°. The longest polyene sequences are formed by PVC. All the polymers except PVC show some complexity of products in the elimination reaction.

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Benzene is an omnipresent liquid in industries. The occupational exposure to benzene leads to the urinary excretion of benzene metabolites, viz., phenol, pyrocatechol, hydroquinone, and trihydroxybenzene, due to its biotransformation. These metabolites are phenolic in nature and considered as immediate biomarkers of benzene exposure. The present work includes the separation and determination of urinary phenolic benzene metabolites by coupling two different techniques. Thin-layer chromatography (TLC) was used as the separation technique to get individually separated spots of all four metabolites, which were further quantified by ultraviolet (UV)–visible spectroscopy at 765 nm. For the development of the separated spots on TLC plate and determination of metabolites by UV–visible spectroscopic method, alkaline Folin‒Ciocalteau reagent was used. Folin‒Ciocalteau reagent is having wide applications for phenol determination and gives blue color with almost all types of phenols. The colored solutions were measured against the blank disk taken from the developed spots on plastic TLC plate. Based on the obtained results, a simple, rapid, and sensitive method for the quantitation of urinary phenolic benzene metabolites has been developed and validated according to the International Conference on Harmonization (ICH) guidelines. The validated method was efficaciously applied to cigarette smokers and petrol station workers, and it was found that the method has favorable application in the routine analysis of urine samples of benzene-exposed population.

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