Comparison of H2O2/UV, H2O2/O3 and H2O2/Fe2+ processes for the decolorisation of vinylsulphone reactive dyesTanja Kurbus
, Alenka Majcen Le Marechal
, Darinka Brodnjak-Vončina
, 2003, izvirni znanstveni članek
Opis: Six vinylsulphone reactive dyes were decolorised using three oxidation processes (H2O2/UV, H2O2/O3 and H2O2/Fe2+). The efficiency of decolorisation was measured by decolorisation time, absorbance, COD and TOC and the three methods of decolorisation are compared.
Ključne besede: textile reactive dyes, vinylsulphone dyes, decolorisation, hydrogen peroxide, UV irradiation, ozone, Fenton's reagent, pollution parameters, experimental design
Objavljeno: 01.06.2012; Ogledov: 1106; Prenosov: 59
Povezava na celotno besedilo
Statistics for business and economicsDavid Ray Anderson
, Dennis J. Sweeney
, Thomas Arthur Williams
, Jim Freeman
, Eddie Shoesmith
Ključne besede: statistics, statistical methods, commercial business, economy, probability, distributions, sampling, analysis of variance, experimental design, regression analysis, forecasting, analysis
Objavljeno: 06.06.2012; Ogledov: 688; Prenosov: 15
Povezava na celotno besedilo
Isolation and Characterisation of Flavonoids From Citrus PeelsKatja Makovšek
, 2013, doktorska disertacija
Opis: Citrus flavonoids are very interesting for food and pharmaceutical industry since they possess many antioxidant properties and biological activities. Mandarin peels represent an important source of hesperidin and polymethoxy flavones nobiletin and tangeretin. Pommelo peels represent an important source of naringin that can be used as precursor for naringin dihdydro-2,3-chalcone artificial sweetener. Since pommelo peels possess good antioxidant and antimicrobial properties, their extracts are very interesting products for food industry. Therefore isolation of flavonoid from mandarin and pommelo peels is an important topic of investigations.
The investigation of the doctoral dissertation is divided in four parts. The first part is focused on the determination of the optimal conditions for the isolation of hesperidin and naringin from mandarin and pommelo peels by conventional extraction. The optimal conditions and the influence of extraction parameters are determined by Taguchi methodology. Very good isolation efficiency of hesperidin, 61.3 mg HES from 1 g of mandarin peels, was obtained by 70 % acetone solution and extraction conditions: 60 °C, 90 min, material to solvent ratio 1/50 g/mL and 3 stages of extraction. The highest amount of naringin, 32.8 mg NAR were isolated from 1 g of material at conditions: conventional extraction, 120 min, albedo, 60 % ethanol, material to solvent ratio 1/50 g/mL and 60 °C. The simple procedure of conventional extraction shows results comparable to more sophisticated methods such as extraction with microwave and ultrasound. Taguchi experimental design was proved to be an efficient methodology to determine the optimal conditions and the parameters that significantly influence product properties.
The second part of the investigation focuses on the characterization of mandarin and pommelo peel extracts and their antioxidant properties. Radical scavenging activity against DPPH and antioxidant capacity of lipid soluble and water soluble compounds were determined for mandarin and pommelo extracts. Taguchi experimental design was applied for determination of the influence of extraction parameters on antioxidant properties. The optimal conditions to prepare extracts with high antioxidant properties were also determined.
In the third part the investigation focuses on the concentration and separation of citrus flavonoids by extraction with supercritical fluids. Supercritical CO2 was applied for the separation of polymethoxylated flavones (PMF) and flavanone glycoside from mandarin peels. The optimal conditions and the parameter influence on the separation were determined by using Taguchi experimental design. The influence of supercritical fluid extraction parameters on material pre-treatment and isolation of flavonoids was studied. These investigations show that supercritical CO2 is a potential solvent for isolation and separation of PMF from mandarin peels.
The fourth and last part of the investigation focuses on the concentration of flavonoids in extract solutions. Since membrane separation processes are very interesting concentration methods in industry, microfiltration, ultrafiltration, nanofiltration and revese osmosis were used for concentration of mandarin and pommelo peel extract solutions. Microfiltration and ultrafiltration could be used in the separation steps after extraction, since they did not influence the amount of dry material and valuable compounds in tested solutions. Reverse osmosis and nanofiltration were shown as useful methods for separation of solvent from extract solutions.
Ključne besede: Flavonoids, hesperidin, naringin, citrus peels, mandarin (Citrus reticulata), pommelo (Citrus maxima), conventional extraction, supercritical fluid extraction, membrane separation processes, Taguchi experimental design
Objavljeno: 22.04.2013; Ogledov: 2422; Prenosov: 235
Celotno besedilo (10,49 MB)
Influence of process parameters on the extraction of flavanones from mandarin peelKatja Makovšek
, Željko Knez
, Mojca Škerget
, 2012, izvirni znanstveni članek
Opis: Flavanones are an important group of flavonoids that are characteristic for citrus. In the present work isolation of flavanones from mandarin peel was performed by conventional extraction using water, ethanol, acetone and aqueous solutions of acetone and ethanol. The extracts were analysed on the content and composition of flavanones. Furthermore the DPPH radical scavenging activity of extracts was determined. Finally, the influence of extraction parameters (particle size, extraction temperature, extraction time,material to solvent ratio, number of extraction stages and type of solvent) on the yield and the efficiency of extraction were determined by Plackett-Burman experimental design.
The results showed that 70% aqueous solution of acetone was the most efficient solvent for isolation of flavanones from mandarin peel. The main flavanones present in the obtained extracts were hesperidin (HES) and narirutin (NRT). The number of extraction stages influenced the yield of extraction, type of solvent influenced the hesperidin extraction efficiency and particle size of material influenced the narirutin extraction efficiency.
Ključne besede: conventional extraction, mandarin peel, flavanone, hesperidin, narirutin, Plackett-Bauman experimental design
Objavljeno: 10.07.2015; Ogledov: 635; Prenosov: 18
Celotno besedilo (231,88 KB)
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