Opis: This study was designed to evaluate antimicrobial and antioxidant activities of the mint extracts from Mentha piperita L. and Mentha aquatica L. In vitro antibacterial activity against two foodborne bacteria (Listeria monocytogenes, Staphylococcus aureus) was evaluated by the well diffusion method. The activity was assessed by the diameter of the inhibition zone. Four of the five extracts from Mentha piperita were active against S. aureus, but none of the extracts was active against L. monocytogenes. Extracts obtained from Mentha aquatica showed no activity against both foodborne bacteria. The horseradish peroxidase/guaiacol assay was used to investigate in vitro antioxidant activity of two mint extracts (Mentha piperita and Mentha aquatica). The ascorbic acid was tested as a reference compound with known antioxidant activity to validate our approach. Extracts from Mentha aquatica showed strong antioxidant activity, but on the other hand, extracts from Mentha piperita showed no antioxidant activity.Najdeno v: ključnih besedahPovzetek najdenega: ...study was designed to evaluate antimicrobial and antioxidant activities of the mint extracts from Mentha... ...and Mentha aquatica L. In vitro antibacterial activity against two foodborne bacteria (Listeria monocytogenes, Staphylococcus...Ključne besede: preservatives, Listeria monocytogenes, Staphylococcus aureus, antimicrobial activity, antioxidant activity, mint extractsObjavljeno: 21.04.2011; Ogledov: 849; Prenosov: 36 Polno besedilo (1,10 MB)
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. Najdeno v: ključnih besedahPovzetek najdenega: ...compounds. Red wines are rich in phenolic antioxidants while white wines generally show lower (poly)phenolic...Ključne besede: white grapes, white wine, maceration, antioxidant activity, polyphenols, extraction, PLE, SFE.Objavljeno: 05.04.2012; Ogledov: 637; Prenosov: 36 Polno besedilo (5,65 MB)