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31.
FOOD PROCESSING WASTES AS POTENTIAL SOURCE OF BIOLOGICALLY ACTIVE COMPOUNDS
Branka Mozetič Vodopivec, 2018, published scientific conference contribution (invited lecture)

Keywords: food processing wastes, wine, olive oil, extraction methods, polyphenols
Published in RUNG: 10.09.2018; Views: 3780; Downloads: 0
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32.
PRIPRAVA IN SENZORIČNA OCENA AROMATIZIRANEGA VINJAKA
Tina Žorž, 2018, undergraduate thesis

Abstract: V diplomskem delu smo obravnavali vpliv dodane naravne arome karamela na senzorične lastnosti vinjaka. V staran vinjak smo dodali 3 različne koncentracije naravne arome karamela, ki smo jo dobili na trgu v prosti prodaji. Aroma je namenjena tako živilskim kot tudi farmacevtskim izdelkom in vsebuje naravne komponente arome karamela. Senzorično oceno smo izvedli s pomočjo uradnega panela Kmetijsko gozdarskega zavoda Nova Gorica in ocenjevalnega lista, ki smo ga povzeli iz literature. V okviru senzorične ocene je ocenjevalna komisija pripravljene vzorce ocenjevala z opisno analizo in kvalifikacijsko analizo. Med potrošniki pa smo izvedli tudi test všečnosti. Rezultati diplomske naloge nakazujejo, da dodatek izbrane naravne arome karamela vinjaku v najnižji koncentraciji (5 ml/l), ki smo ga uporabili v diplomski nalogi, najbolje pripomore k boljši aromatiki in zaokroženemu okusu. Opazili smo, da dodatek arome v vinjak navkljub odsotnosti sladkorja pripomore k večji zaznavi sladkosti v okusu in k zakrivanju zaznavanja alkohola, kar je najverjetneje botrovalo preferenčnim razlikam med moškim in ženskim okusom do izbranih alkoholnih pijač. Ženske in mlajše generacije so se na splošno odločale za bolj aromatizirane vzorce, moške pa sta bolj prepričala osnovni vzorec in vzorec z majhnim dodatkom karamele.
Keywords: vinjak, aroma karamele, senzorična ocena, analiza potrošnikov
Published in RUNG: 30.07.2018; Views: 7255; Downloads: 255
.pdf Full text (1,97 MB)

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Simple and fast HPLC-DAD method for determination of HCDC activity and formation of vinylphenol in Saccharomyces and non-Saccharomyces yeast
Jelena Topič, Lorena Butinar, Dorota Korte, Branka Mozetič Vodopivec, published scientific conference contribution abstract

Abstract: Conventionally, alcoholic fermentation in the production of wine is performed by yeast species Saccharomyces cerevisiae. There are numerous starters available, however due to the growing demand for wines with specific characteristics, other Saccharomyces and non-Saccharomyces species are being investigated for potential use as starters. [1]. Yeast selection has involved the development of techniques for detecting strains that might improve wines in terms of aroma, structure, colour and other technological properties [2]. Colour of the wine can be affected as some metabolites produced by yeast during fermentation may react with grape anthocyanins to produce highly stable pyranoanthocyanins. For the facilitation of formation of vinylphenolic pyranoanthocyanins, yeast strains with high hydroxycinnamate decarboxylase activity are used (HCDC). The mechanism of reaction is decarboxylation of hydroxycinnamic acids and formation of vinylphenols that condense with grape anthocyanins and form stabile vinyphenolic pyranoanthocyanin adducts [3]. It has been demonstrated that some non-Saccharomyces strains (Pichia guillermondii, Schizosaccharomyces pombe) have positive HCDC activity and they can produce vinylphenolic pyranoanthocyanins in higher concentrations than S. cerevisiae. A simple way of determining whether the yeast strain has HCDC activity or not, is the use of fermentation media with the addition of hydroxycinnamic acids, such as p-coumaric acid. The degradation of p-coumaric acid and transformation into 4-vinylphenol (and possibly in 4-ethylphenol) can be checked by LC-DAD. Most of the published data has been done on smaller number of strains. The goal of our work was to develop simple method for the screening of Slovenian in-house yeast collection, comprising of native isolates that mostly originated from Vipava valley and Karst region, and therefore try to determine strains with high HCDC activity. These strains can be used for wine fermentations in order to produce more stable pyranoanthocyanins; which is especially important in wines that has less anthocyanin concentration already from the grape, such as Pinot Noir. 103 different yeast strains belonging to 28 species were selected for the assessment of HCDC activity. In some cases the difference in p-coumaric acid metabolism rate between two strains exceeded 90%. All tested S. paradoxus strains showed higher than 40% degradation rate of p-coumaric acid. HCDC activity of S. cerevisiae strains which is the species most commonly used in fermentation, varied between 5.1 and 66.1%. The commercial strains tested, FPC and EC118 showed 43.9 and 21.5% conversion rate, respectively. It was observed that some native strains had higher HCDC activity than commercial tested ones. Three strains produced vinylphenol in concentration higher than 50 ppm, two of them being P. guillermondii and another strain being S. paradoxus (Sut85). In general strain with high HCDC activity also produced high concentration of 4-vinylphenol. The results showed that HCDC activity is highly strain dependent, which correlates with the literature data available. The proposed method is very simple and does not require special sample preparation prior to HPLC analysis. Furthermore, the proposed fermentations in deep-well microtiter plates allow the screening of high number of strains. The method could be used for routine screening, to determine which strain has high HCDC activity and produces high concentration of vinylphenols and can therefore be used in future for determination of strains ability to synthesize vinylphenolic pyranoanthocyanins.
Keywords: yeast, hydroxycinnamate decarboxylase, 4-vinylphenol
Published in RUNG: 18.06.2018; Views: 4293; Downloads: 0
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35.
Vpliv različnih bentonitov na senzorične in kemijske lastnosti vina sorte 'Rebula' (Vitis vinifera L.)
Uroš Špacapan, 2018, undergraduate thesis

Abstract: Pomemben dejavnik pri kakovosti vina ter posledično tudi pri uspešni prodaji je stabilnost vina v steklenici, kajti v nasprotnem primeru pride do slabega ugleda vinarja in tudi zavračanja proizvoda na trgu. Beljakovinsko stabilnost vina lahko dosežemo na več načinov, ki pa so odvisni od same tehnologije in tudi trendov na vinskem trgu. V sklopu diplomske naloge smo preučevali vpliv uporabe štirih različnih bentonitov na kemijske in senzorične lastnosti vina sorte Rebula. Vino smo pred stekleničenjem tretirali z različnimi komercialno dostopnimi bentoniti in stekleničena vina kemijsko ter senzorično ovrednotili. Poleg določanja osnovnih kemijskih parametrov smo spektrofotometrično določili vsebnost skupnih fenolov in barve vina. S pomočjo encimskih kitov smo določili tudi vsebnost vinske, jabolčne in mlečne kisline v stekleničenih vinih. Rezultati našega poskusa kažejo, da je uporaba različnih bentonitov vplivala tako na kemijske kot tudi na senzorične lastnosti vina. V vinih tretiranih z bentonitom smo zaznali rahel trend nižjih vsebnosti alkohola ter skupnih titrabilnih in hlapnih kislin. Obenem pa smo zaznali tudi trende povečanja parametrov, kot je barva vina (absorbanca pri 420 nm) in vsebnosti skupnih fenolov primerjavi s kontrolnim – netretiranim vzorcem. Senzorična ocena tretiranih vin je nakazala trend siromašenja sadnih not pri vseh uporabljenih bentonitih, v določenih primerih pa, nasprotno, pozitivne vplive na zaznane cvetlične in rastlinske note. Rezultati so tako pokazali, da vrsta bentonita različno vpliva na senzorične lastnosti vina Rebula.
Keywords: vino Rebula, belo vino, bentonit, kemijski parametri vina, senzorične lastnosti vina
Published in RUNG: 13.02.2018; Views: 6968; Downloads: 268
.pdf Full text (1,62 MB)

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Biodiversitet i naturleg gjær i siderproduksjonen i Hardanger
Lorena Butinar, Eivind Vangdal, Melita Sternad Lemut, Branka Mozetič Vodopivec, 2017, professional article

Keywords: biodiverziteta, kvasovke, jabolčno vino, fermentacija
Published in RUNG: 01.02.2018; Views: 4957; Downloads: 0
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