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1.
GRAPE ANTIOXIDANTS - INFLUENCE OF PROCESSING PARAMETERS ON THEIR CONTENT AND ACTIVITY
Iva 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
.pdf Celotno besedilo (5,65 MB)

2.
Polyphenols: extraction methods, antioxidative action, bioavailability and anticarcinogenic effects
Eva Brglez Mojzer, Maša Knez Hrnčič, Mojca Škerget, Željko Knez, Urban Bren, 2016, izvirni znanstveni članek

Opis: Being secondary plant metabolites, polyphenols represent a large and diverse group of substances abundantly present in a majority of fruits, herbs and vegetables. The current contribution is focused on their bioavailability, antioxidative and anticarcinogenic properties. An overview of extraction methods is also given, with supercritical fluid extraction highlighted as a promising eco-friendly alternative providing exceptional separation and protection from degradation of unstable polyphenols. The protective role of polyphenols against reactive oxygen and nitrogen species, UV light, plant pathogens, parasites and predators results in several beneficial biological activities giving rise to prophylaxis or possibly even to a cure for several prevailing human diseases, especially various cancer types. Omnipresence, specificity of the response and the absence of or low toxicity are crucial advantages of polyphenols as anticancer agents. The main problem represents their low bioavailability and rapid metabolism. One of the promising solutions lies in nanoformulation of polyphenols that prevents their degradation and thus enables significantly higher concentrations to reach the target cells. Another, more practiced, solution is the use of mixtures of various polyphenols that bring synergistic effects, resulting in lowering of the required therapeutic dose and in multitargeted action. The combination of polyphenols with existing drugs and therapies also shows promising results and significantly reduces their toxicity.
Ključne besede: polyphenols, extraction, antioxidants, bioavailability, synergistic effects
Objavljeno: 22.06.2017; Ogledov: 404; Prenosov: 322
.pdf Celotno besedilo (1,38 MB)
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3.
Chemometric characterization of Slovenian red wines
Milena Ivanović, Anja Petek, Maša Islamčević Razboršek, Mitja Kolar, 2017, izvirni znanstveni članek

Opis: Total phenolic (TPC), flavonoid (TFC) and tannin (TTC) contents, total $SO_2$, total acids, pH, and reducing sugars were measured in twenty five Slovenian red wines from three key wine producing regions, Podravje, Posavje and Primorska. The results were chemometrically analysed and the wines were classified according to wine growing region and vine variety. Principal component analysis proved that TPC, TFC and TTC contents were primarily responsible for variation in the wines. Additionally, linear discriminant analysis (LDA) was performed and resulted in the satisfactory classification of samples by both vine variety and region.
Ključne besede: Slovenian red wines, quality parameters of wine, polyphenols, chemometric analysis
Objavljeno: 03.10.2017; Ogledov: 432; Prenosov: 188
.pdf Celotno besedilo (119,46 KB)
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