Dorina Chambre

Improved DPPH determination for antioxidant activity spectrophotometric assay

An improved procedure for determination of the residual DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical concentration was proposed taking into account the absorbance of both DPPH free radicals and DPPH nonradical (1,1-diphenyl-2-picrylhydrazine) stable form. The calculated residual DPPH free radical concentrations were compared with those obtained from a calibration curve and variation coefficients below 10 % were found.

TG/DTG/DTA for the oxidation behavior characterization of vegetable and animal fats

TG/DTG/DTA curves can be used to estimate alimentary fats quality and antioxidants insertion efficiency. Sunflower oil obtained from Carnia hybrid and pork lard were used as matrices for the non-isothermal measurements. The first stage of non-isothermal decomposition is mostly important for the characterization of the fats thermal stability. The corresponding onset temperature is a good value for the comparison of different fats thermal stability or for the effectiveness evaluation in case of antioxidant insertion. In this study, it can be seen a considerable improvement of the fats thermal stability by adding small amounts from a natural antioxidant liquid mixture (obtained by alcoholic maceration of equal amounts of seven plants, namely: milfoil, rosemary, marjoram, thyme, lovage, oregano, and basil). Chlorophylls removal from the plant extract using two different adsorbents was accompanied by a four time decrease of the antiradical activity (measured by the DPPH method) with Sephadex LH20 and seventeen times decrease when activated carbon was used.

Non-isothermal Dehydration Kinetics of Some Cationites

The kinetic parameters of dehydration were determined under non-isothermal conditions for different polystyrenedivinylbenzene sulfonic acid type cationites (DVB) and their dependence on the degree of cross-linking granulation, porosity, specific surface, content of SO3M groups (M=Li, Na, K, Rb), nature of the alkali metal in partially neutralized -SO3H groups and heating rate was investigated.

A Comparison of a New Method Mediated by Molybdenum Complex with an Enzymatic Method for Bleaching Flax Fibers

In the last years, the interest in bast fibers for textile products has been growing in line with the necessity for new added-value products. The attention has focused on the research in developing of different methods of processing natural fibers. The main goal of this work was to compare two methods for fiber’s degumming. One method used the molybdenum complex for degumming and the other is an enzymatic one with laccase as catalyst. The physical–mechanical parameters were in the same range for both methods, while the lignin contt was smaller for the molybdenum complex—peroxide process than for the treatment with laccase—peroxide system. The characterization using FT-IR spectroscopy and thermogravimetry also suggest that the treatments with molybdenum complex degraded more lignin than the enzymatic treatments. The crystallinity index of bleached fibers using the system molybdenum complex was higher than for the fibers treated with enzymes while the degrees of whiteness were somehow lower but in the acceptable range.

The influence of high-temperature heating on composition and thermo-oxidative stability of the oil extracted from Arabica coffee beans

The aim of the present study was to establish the influence of high-temperature heating on the composition and thermal behavior of coffee oils obtained from Arabica green and roasted coffee beans, respectively. Morphological studies performed using scanning electron microscopy revealed the oil bodies uniformly distributed within the cells in both types of coffee beans analyzed. The obtained oils have a fatty acid composition rich in linoleic acid, palmitic acid, oleic acid, stearic acid, arachidic acid and linolenic acid. The total content of saturated fatty acids of investigated oils was 49.38 and 46.55%, the others being unsaturated fatty acids. The thermal behavior and thermo-oxidative stability of coffee oils extracted from green coffee beans and roasted coffee beans, the coffee oil high-temperature heated up to 200 °C, were investigated using simultaneous thermal analysis TG/DTG/DTA, in an oxidizing atmosphere. The data obtained for the analyzed samples depend mainly on the nature and compositions of fatty acids, and to a lesser extent on the roasting process of the coffee beans and the high-temperature heating process of the extracted oil. The chromatographic and TG/DTG/DTA data suggest that Arabica coffee oil has great potential for use in technological processes which require high-temperature heating (e.g. food industry or pastries).