GRAPE ANTIOXIDANTS - INFLUENCE OF PROCESSING PARAMETERS ON THEIR CONTENT AND ACTIVITYIva Ružić
, 2012, doktorska disertacija
Opis: 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.
Ključne besede: white grapes, white wine, maceration, antioxidant activity, polyphenols, extraction, PLE, SFE.
Objavljeno: 05.04.2012; Ogledov: 1920; Prenosov: 101
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Potential of phenolic antioxidantsIva Ružić
, Mojca Škerget
, Željko Knez
, 2010, pregledni znanstveni članek
Opis: In vitro studies have shown a link between the consumption of food rich in (poly)phenols, especially flavonoids, and reduced risk of coronary heart diseases. Several flavonoids have been reported to prevent low density lipoprotein cholesterol oxidation in vitro. The aim of our work was to determine antioxidant and radical scavenging activity of flavonoids myricetin,quercetin, rutin, luteolin, apigenin, kaempferol, catechin, epicatechin and epigallocatechin gallate and to study the influence of chemical structure and flavonoid interactions on the ability to inhibit oxidation and scavenge free radicals. Two in vitro methods, i.e. oxidation of â-carotene in an emulsion system and DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging assay, were applied. In addition, a review of in vivo studies that investigate the effectiveness of food flavonoids in reducing oxidative damage in human body was done and their results were analyzed and compared to in vitro results obtained in our laboratory. Although all tested flavonoids except apigenin showed strong antioxidant and antiradical properties in vitro, these findings can not be completely confirmed from the reviewed in vivo human studies since those results are sometimes contradictoryand inconsistent.
Ključne besede: phenolics, flavonoids, antioxidant activity, antiradical activity
Objavljeno: 10.07.2015; Ogledov: 512; Prenosov: 30
Celotno besedilo (250,25 KB)
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A stability assessment of coastal cliffs using digital imageryIgor Ružić
, Čedomir Benac
, Ivan Marović
, Suzana Ilić
, 2015, izvirni znanstveni članek
Opis: The investigated area around the Stara Baška settlement (the island of Krk, NE channel part of the Adriatic Sea) is in a delicate geodynamic balance. Marine erosion is quite prominent and the recorded cliff retreat between 1966 and 2004 was from 4 to 5 metres. The cliff slopes are formed in talus breccias. Strong waves and formations of wave-cut notches are the main causes of the cliff’s instability. The secondary causes are the weathering and erosion of the soil and rocks on the cliff. The slump of the cliff slope can occur in a rock mass with higher strength parameters, where the notches are cut a few metres inward into the toe of the cliff slope. A combined method for the stability analysis of the coastal cliffs was tested; this incorporates the cantilever-beam model and the structure-from-motion (SfM) photogrammetry. This method can provide highly detailed 3D geometrical data of the cliff, which can then be used in the calculations of the stability model. This is particularly important in a stability analysis of lithologically heterogeneous rocks such as breccias with varied geometry, which cannot be easily replaced by a rectangular surface. The simple and useful SfM method overcomes the limitations of traditional surveys in estimating the cliff overhang surface and the notch length.
Ključne besede: marine erosion, cliff stability, SfM photogrammetry, Krk island, Adriatic sea
Objavljeno: 15.06.2018; Ogledov: 280; Prenosov: 16
Celotno besedilo (865,75 KB)
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ENERGIJSKA PRENOVA LESENE MONTAŽNE HIŠETine Ružić
, 2014, diplomsko delo
Opis: Diplomsko delo obravnava teorijo lesene montažne gradnje, energetske prenove enostanovanjskega objekta, vključno s splošnimi principi in razlogi za sanacijo, ukrepi prenove in ekonomsko upravičenostjo teh ukrepov.
V praktičnem delu diplomskega dela sta predstavljeni dve verziji energetske prenove enostanovanjske lesene montažne hiše. S pomočjo izračunov v programu za gradbeno fiziko smo objekt analizirali in spremljali stroške in čas povrnitve prenove objekta v dva različna energetska razreda ter s tem ugotavljali ekonomsko upravičenost analiziranih prenov.
Ključne besede: gradbeništvo, energetska sanacija, montažna gradnja, toplotna izolacija, ekonomska upravičenost
Objavljeno: 16.09.2014; Ogledov: 1259; Prenosov: 263
Celotno besedilo (8,21 MB)