magistrsko delo študijskega programa II. stopnje
Jožica Ulčnik (Author), Mojca Škerget (Mentor), Željko Knez (Co-mentor)

Abstract

Povzetek Magistrsko delo prikazuje študijo možnosti uporabe subkritične vode kot hidroliznega medija za selektivno razgradnjo glikozidno vezanih antioksidantov v ekstraktu rdeče ptujske čebule. Iz neizkoriščenih čebulnih olupkov smo želeli pridobiti kvercetin, kot produkt z visoko dodano vrednostjo. S pomočjo konvencionalne ekstrakcije čebulnih olupkov smo pridobili čebulni ekstrakt, le-temu smo določili vsebnost totalnih fenolov v ekstraktu s Folin-Ciocalteu metodo. Ekstrakt smo hidrolizirali po postopku kislinske hidrolize s HCl in s tem določili vsebnost totalnega kvercetina v ekstraktu. Preučevali smo vpliv parametrov (temperatura, tlak in uporabljena vrsta plina v avtoklavu, kontaktni čas in koncentracija raztopine ekstrakta) na izkoristek hidrolize s subkritično vodo v šaržnem reaktorju. Na podlagi optimalnih pogojev v šaržnem reaktorju smo izvedli kontinuirno hidrolizo ekstrakta s subkritično vodo. Kvalitativno in kvantitativno vsebnost kvercetina v hidroliziranih vzorcih smo določili s HPLC analizo. Rezultati kažejo, da smo najvišji izkoristek ekstrakcije dosegli pri ekstrakciji zmlete mešanice olupka in jedilnega dela čebule z vodo pri temperaturi 95 °C. Najvišjo vsebnost totalnih fenolov smo določili v ekstraktu čebulnega olupka, pridobljenega s 35 % raztopino etanola pri 80 °C. Najvišji odstotek hidrolize smo s šaržnim procesom dosegli pri 195 °C, kontaktnem času 12,5 min, uporabi CO2 pri tlaku 215 bar in koncentraciji raztopine ekstrakta 0,1 mg/ml. Na podlagi rezultatov HPLC meritev sklepamo, da pri šaržnem procesu, z naraščajočo koncentracijo vodne raztopine čebulnega ekstrakta odstotek hidrolize pada. Najvišji odstotek hidrolize pri kontinuirnem procesu smo dosegli pri temperaturi 200 °C, tlaku 102 bar, kontaktnem času 12,9 min in koncentraciji raztopine ekstrakta 0,5 mg/ml. HPLC analiza je pokazala, da kot stranska produkta med potekom hidrolizne reakcije poleg ostalih komponent nastajata 3,4-dihidroksi benzojska kislina in 5-hidroksi metil furfural, ki ga lahko zaradi razlik v topnosti v vodi separiramo od kvercetina.

Keywords

olupki rdeče čebule;glikozidi;subkritična voda;hidrokvercetin;magistrske naloge;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [J. Ulčnik]
UDC: 66.094.941:635.25(043.2)
COBISS: 20304662 Link will open in a new window
Views: 1174
Downloads: 118
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Other data

Secondary language: English
Secondary title: HYDROLYSIS OF GLYCOSIDE BOUNDED ANTIOXIDANTS IN ONION EXTRACT WITH SUBCRITICAL WATER
Secondary abstract: Abstract This master thesis describes the possible usage of subcritical water as hydrolysis medium for selective decomposition of glycoside bounded antioxidants in red onion peel extract. The main intention was to obtain quercetin from unused red onion peels as a material with added value. Convencional extraction of onion peels enabled us to obtain the onion peel extract. The content of total phenols in the extract was determinated with the Folin-Ciocalteu reagent. The extract was hydrolyzed according to the procedure of acid hydrolysis with HCl and the total amount of quercetin in the extract was determined. We studied the effect of reaction parameters (temperature, pressure and type of gas in autoclave, contact time and concentration of extract solution) on efficiency of hydrolysis with subcritical water in batch reactor. Using optimal conditions in the batch reactor, continuous hydrolysis of extract with subcritical water was performed. Qualitative and quantitative content of quercetin in hydrolysed samples was determined with HPLC analysis. Results show that the highest amount of extract was acquired when the grinded mixture of peels and eadible part of onion was extracted by water at a temperature of 95 °C. The highest content of total phenols was determined in extract of onion peels that was obtained with a 35 % ethanol solution at 80 °C. The highest percentage of hydrolysis performed in batch process was achieved at 195 °C, at a contact time of 12.5 minutes, using CO2 at a pressure of 215 bar and a concentration of extract solution of 0.1 mg/ml. Based on results of HPLC measurements we can conclude that the percentage of hydrolysis in batch process is decreasing by increasing concentration of water solution of onion extract. The highest percentage of hydrolysis performed in continuous mode was achieved at a temperature of 200 °C, pressure of 102 bar, treatment time of 12.5 min and 0.5 mg/ml concentration of extract solution. HPLC analysis indicated that during the hydrolysis reaction, 5-hydroxymethylfurfural and 3,4-dihydroxybenzoic acid are produced as side products, however 5-HMF could be separated from quercetin, due to differences in solubility in water.
Secondary keywords: red onion peel;glycosides;hydrolysis;subcritical water;quercetin;
Type (COBISS): Master's thesis/paper
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: 78 str.
ID: 9153656