Najdeno v: osebiKljučne besede: chemical processing, high pressure technology, extraction, CO2, natural antioxidants, rosemary extract, food additivesObjavljeno: 31.05.2012; Ogledov: 167; Prenosov: 4 Polno besedilo (0,00 KB)
Opis: This article presents a newly developed method for the determination of low levels of antioxidants, present in meat and meat products. The method is a high performance liquid chromatography (HPLC), using coulometric electrochemical detector. An oil soluble antioxidant, carnosic acid, extractedfrom rosemary was used as a target compound.. Usual dosage of carnosic acid as an antioxidant in meat and meat products is 0.0040% (40 mg/kg), calculated on fat content. The ability to accurately measure low levels of antioxidants in food would be of great advantage to the food industry, because it would improve the process of partitioning of antioxidantsin to food system, which would lead to improved food stability and better prediction of its shelf life. The selectivity and sensitivity of the coulometric array are the key properties that were required for the analysis presented in this article. A coulometric technique is well suited for the determination of low levels of analyte and is one of the most sensitive analytical approaches available today.Najdeno v: osebiObjavljeno: 31.05.2012; Ogledov: 117; Prenosov: 2 Polno besedilo (0,00 KB)
Opis: Methanol extracts prepared from five plant materials native to the Mediterranean area, namely olive tree (Olea europaea) leaf, St. John's wort (Hypericum perforatum), hawthorn (Crataegus laevigata), oregano (Origanum vulgare) and laurel leaf (Lauris nobilis), were examined for their phenolic components. Total phenolic content was determined by the Folin-Ciocalteu method. The content of proanthocyanidins in acid-hydrolysed extracts was determined spectrophotometrically. The contents of free flavones (apigenin andluteolin) and flavonols (kaempferol, myricetin and quercetin) were determined by HPLC analysis. The time of hydrolysis of flavones, flavonols andproanthocyanidins was optimised. Antioxidant activities of apigenin, luteolin, kaempferol, myricetin, quercetin and of plant extracts were examined. Antioxidative activities were studied in sunflower oil at 98 °C, by measuring peroxide value, and in an aqueous emulsion system of -carotene and linoleic acid by measuring the absorbance of the sample. Among flavones and flavonols investigated, only myricetin inhibited oxidation of sunflower oil. All other flavones and flavonols showed pro-oxidative activity. Oppositely, in the emulsion system, only apigenin showed pro-oxidative activity while otherflavones and flavonols and plant extracts inhibited oxidation of -carotene.Najdeno v: osebiKljučne besede: chemical processing, extraction, plant material, fenolic content, hidrolysis, antioxidants, flavones, flavonols, proanthocyanidines, oils, emulsionsObjavljeno: 01.06.2012; Ogledov: 176; Prenosov: 1 Polno besedilo (0,00 KB)
Najdeno v: osebiKljučne besede: kemijska procesna tehnika, visokotlačna tehnologija, ekstrakcija, rožmarinska kislinaObjavljeno: 01.06.2012; Ogledov: 241; Prenosov: 3 Polno besedilo (0,00 KB)
Opis: In present work, the purification of crude rosemary extract with supercritical fluids is presented. Carbon dioxide was used as a solvent. The crude extract was prepared from rosemary with conventional extraction process. The supercritical CO2 extraction of crude extracts was performed at pressures 10 and 20 MPa and temperatures 35 and 60 °C. The best results were obtained at pressure 10 MPa and temperature 35 °C. The content of carnosic acid in the samples before and after high pressure extraction was identified by high performance liquid chromatography. The content of carnosic acid in purified extract is higher compared to crude extract. The antioxidative efficiency of extracts was determined by measuring peroxide value. Activity ofpurified rosemary extracts is higher compared to crude extracts.Najdeno v: osebiKljučne besede: chemical processing, high pressure technology, extraction, CO2, natural antioxidants, rosemary extract, food additivesObjavljeno: 01.06.2012; Ogledov: 159; Prenosov: 0 Polno besedilo (0,00 KB)
