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Title:GRAPE ANTIOXIDANTS - INFLUENCE OF PROCESSING PARAMETERS ON THEIR CONTENT AND ACTIVITY
Authors:ID Ružić, Iva (Author)
ID Knez, Željko (Mentor) More about this mentor... New window
ID Škerget, Mojca (Co-mentor)
Files:.pdf DR_Ruzic_Iva_2012.pdf (5,65 MB)
MD5: CDF4F55B2695E2C28A33A2956D9882A8
PID: 20.500.12556/dkum/3e93e168-3a64-4867-a5ab-d485834c8156
 
Language:English
Work type:Dissertation
Organization:FKKT - Faculty of Chemistry and Chemical Engineering
Abstract:Grapes and wine production residuals, containing grape skins, seeds and stems, represent important sources of phenolic compounds. Red wines are rich in phenolic antioxidants while white wines generally show lower (poly)phenolic content and antioxidant activity. The main difference in the production of white and red wines is the fermentation step. The fermentation of red grapes includes maceration, i.e. it takes place in both liquid and solid parts of the grape. In the case of white wines, the must is clarified before the fermentation starts, cultured yeasts are added to convert the must to wine and antioxidant sulfur dioxide is inserted to protect the wine. The objective of the PhD research was to study antioxidant potential of white grape phenolics both in raw material and fermentation products. First, the standards of phenolic compounds commonly found in white grapes and wines were tested for their antioxidant and antiradical activity. All tested compounds except apigenin showed strong antioxidant and antiradical properties. Afterwards, conventional solid-liquid extraction (CE) and pressurized liquid extraction (PLE) of phenolic compounds from grape seeds were performed. The optimal extraction conditions were investigated and extracts were analyzed in order to determine their total phenolic content, individual phenolic compounds and antiradical potential. Two different drying methods (hot air and freeze drying) were applied to the seeds. Solvent efficiencies of water, ethanol and water-ethanol mixtures were compared at different temperatures. In addition, supercritical fluid extraction (SFE) with CO2 was investigated as the technique for the recovery of phenolic compounds and for the pretreatment of white grape seed samples. Both CE and PLE gave extracts rich in phenolic compounds with good antiradical properties and, generally, the best results were obtained with PLE at 130°C. At the end, the influence of maceration process on the content and the activity of grape phenolic antioxidants in white wines was studied. For such a purpose, six commercially available macerated white wines from Italy and Croatia were analyzed. In addition, eight non-macerated wines from the same region and variety were studied and compared to macerated wines. The experiments have shown that the maceration process increases the total phenolic content and antiradical activity of the wine. It enables the production of white wines rich in phenolic compounds and with strong antiradical properties in completely natural way using only the grapes and without addition of any chemical agents.
Keywords:white grapes, white wine, maceration, antioxidant activity, polyphenols, extraction, PLE, SFE.
Place of publishing:Maribor
Publisher:[I. Ružić]
Year of publishing:2012
PID:20.500.12556/DKUM-22552 New window
UDC:66.063.4:634.852(043.3)
COBISS.SI-ID:15929110 New window
NUK URN:URN:SI:UM:DK:BXGWCCZD
Publication date in DKUM:05.04.2012
Views:2846
Downloads:176
Metadata:XML RDF-CHPDL DC-XML DC-RDF
Categories:KTFMB - FKKT
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Secondary language

Language:Slovenian
Title:GROZDNI ANTIOKSIDANTI - VPLIV PROCESNIH PARAMETROV NA NJIHOVO VSEBNO IN DEJAVNOST
Abstract:Grozdje in ostanki vinske proizvodnje kot so grozdne lupine, pečke ter grozdna stebla, predstavljajo pomemben vir fenolnih spojin. Rdeča vina so bogata s fenolnimi antioksidanti, medtem ko bela vina v splošnem kažejo nižjo polifenolno vsebnost in antioksidativno aktivnost. Glavna razlika v proizvodnji rdečih in belih vin je v fermentaciji, saj fermentacija rdečih vin vključuje maceracijo, kar pomeni, da sodelujejo tako trdi kot tekoči deli grozdja. V primeru belih vin pa imamo pred pričetkom fermentacije očiščen mošt, temu dodamo kvasne kulture, ki ga pretvorijo v vino, kateremu dodamo antioksidant žveplov dioksid. Namen doktorske raziskave je bila študija antioksidativnega potencijala fenolov belega grozdja v surovem stanju ter v fermentacijskih produktih. Najprej je bilo izvedeno testiranje fenolnih spojin, ki se najpogosteje nahajajo v belem grozdju in vinu, da bi določili njihovo antioksidativno aktivnost ter vpliv na proste radikale. Vse testirane spojine razen apigenina so pokazale močne antioksidativne in antiradikalne lastnosti. Izvedene so bile tudi klasične ekstrakcije trdno-tekoče (CE) in pospešene ekstrakcije pri povišanem tlaku (PLE) fenolnih spojin iz grozdnih semen. Raziskani so bili optimalni pogoji za ekstrakcijo kot tudi celotna vsebina fenolov, individualne fenolne spojine ter antiradikalne lastnosti dobljenih ekstraktov. Izvedeni sta bili dve različni metodi sušenja semen, z vročim zrakom ter z zamrzovanjem. Primerjane so bile tudi topne lastnosti vode, etanola ter mešanic omenjenih topil pri različnih temperaturah. Dodatno je bila raziskana ekstrakcija s superkritično CO2 kot tehnika za pridobitev fenolnih spojin in predpriprava vzorcev grozdnih semen. Oba postopka ekstrakcije sta dala kot rezultat ekstrakte bogate s fenolnimi spojinami z dobrimi antiradikalnimi lastnostmi, najboljši rezultati pa so bili doseženi s PLE pri 130°C. Na koncu je bil raziskan še vpliv maceracije na vsebino ter aktivnost grozdnih fenolnih antioksidantov v belih vinih. Za te namene je bilo analiziranih šest različnih komercialno dobavljivih maceriranih belih vin iz Italije in Hrvaške, za primerjavo pa je služilo osem nemaceriranih vin iz istih področij. Eksperimentalno je bilo ugotovljeno, da proces maceracije poveča skupno fenolno vsebnost in antiradikalno aktivnost vina, ta vpliv pa lahko s pridom izkoristimo v proizvodnji vin, saj lahko proizvedemo vina bogata s fenoli ter močnimi lastnostmi proti prostim radikalom le z uporabo grozdja ter brez dodatkov kemičnih sredstev.
Keywords:belo grozdje, belo vino, maceracija, antioksidativna aktivnost, polifenoli, ekstrakcija, PLE, SFE.


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