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Opis: Early leaf removal around the cluster zone is a common technique applied in cool climate viticulture, to regulate yield components and improve fruit quality. Despite the increasing amount of information on early leaf removal and its impact on total soluble solids, anthocyanins and polyphenols, less is known regarding aroma compounds. In order to verify the hypothesis that defoliation, applied before or after flowering, could impact the biosynthesis of thiol precursors, we performed a two year (2013 and 2014) experiment on Sauvignon blanc. We provided evidence that differential accumulation of thiols precursors in berries is affected by the timing of defoliation and this impact was related to modifications in biosynthetic pathway. Furthermore, the possible interaction between leaf removal treatment and seasonal weather conditions, and its effect on the biosynthesis of volatile precursors are discussed. Our results suggested that in Sauvignon blanc the relative proportion of 4-S-glutathionyl-4-methylpentan-2-one (G-4MSP) and 3-S-glutathionylhexan-1-ol (G-3SH) precursors can be affected by defoliation, and this could be related to the induction of two specific genes encoding glutathione-S-transferases (VvGST3 and VvGST5), while no significant effects on basic fruit chemical parameters, polyphenols and methoxypyrazines were ascertained under our experimental conditions.
Ključne besede: early leaf removal, cluster exposure, thiol precursors, methoxypyrazines, glutathione S-transferase, Vitis vinifera
Objavljeno v RUNG: 31.08.2017; Ogledov: 5696; Prenosov: 0
Gradivo ima več datotek! Več...

Opis: The aim of this study was to explore the diversity of fermentative yeast species in a non-vineyard and vineyard environment, and exploit their oenological potential. For this purpose we collected plant and soil material in the vineyard (located in Črniče in Vipava Valley) planted with Vitis vinifera L. and in the forest (forest in Vipava Old Castle), and by using a selective medium with high ethanol and sugar content we managed to obtain 35 isolates. By sequencing the D1/D2 domain of the 26S rDNA we identified nine different yeast species. The oenological potential of identified yeasts was further investigated by employing a series of tests, such as growth at low pH values, tolerance to ethanol and sulfur, and H2S production ability. Based on the results of these tests we selected four different yeast species for the microvinification of Vitis vinifera L. cv. ‘Pinot Noir’ grape juice. A commercial strain Saccharomyces cerevisiae Lalvin D47 was also included as a control in the fermentation experiment. Fermentation monitoring was done by measuring daily weight loss and microbiological analysis in the middle of fermentation. For the final wines, sugars were determined and sensorial evaluation performed. Among four tested yeasts, S. paradoxus IVV 32 and Torulaspora delbrueckii IVV 36 appeared to be the most promising for winemaking, but further studies should be carried out.
Ključne besede: wine, Vitis vinifera L. cv. ‘Pinot Noir’, biodiversity, yeasts, fermentation
Objavljeno v RUNG: 10.07.2017; Ogledov: 7921; Prenosov: 291
Celotno besedilo (2,57 MB)

Ključne besede: Zelen (Vitis vinifera L.), targeted metabolomics, wine aroma, sensory evaluation, alternative vinification procedures
Objavljeno v RUNG: 18.04.2017; Ogledov: 7010; Prenosov: 0
Gradivo ima več datotek! Več...

Opis: Poleg sorte, geo-klimatskih pogojev in vinogradniških strategij v vinogradu so tudi vinarjeve odločitve glede izbora vinifikacijskih postopkov tiste, ki lahko odločilno vplivajo na končno kakovost vina, vključno z njegovimi aromatskimi značilnostmi. Z različnimi prijemi ali postopki pred alkoholno fermentacijo in med njo lahko vplivamo predvsem na ekstrakcijo in ohranitev primarnih ter na tvorbo sekundarnih aromatskih spojin. V okviru diplomskega dela smo s pomočjo modernih analitskih pristopov metabolnega profiliranja in tehnike GC/MS/MS preučevali vpliv različnih tehnoloških postopkov predelave grozdja (krioekstrakcija s suhim ledom, stik s celimi jagodami med fermentacijo, klasični pristop-kontrola) na vsebnost prostih in vezanih aromatičnih spojin v mladih vinih Zelen, letnik 2014. Preučili smo tudi vpliv obravnavanih tehnologij na senzorične lastnosti, vezane na zaznave vonja v mladih vinih. Rezultati enoletnega poskusa so nakazali, da lahko s pomočjo krioekstrakcije v vinih Zelen povečamo izplene skupnih prostih aromatičnih kislin, estrov in terpenov, po drugi strani pa smo zaznali le trend povečanja vsebnosti skupnih višjih alkoholov pri vzorcih iz postopka dodajanja jagod med fermentacijo. V primeru vezanih aromatskih spojin smo s pomočjo postopka dodajanja jagod v primerjavi s kontrolo opazili trende povečanja vsebnosti nekaterih vezanih estrov, norizoprenoidov in višjih alkoholov, krioekstrakcija pa je večinoma povzročila trende k niţjim vsebnostim vezanih aromatskih spojin glede na kontrolne vzorce. Nazadnje so se tudi senzorična opazovanja z vonjem povezanih lastnosti vin zaključila preteţno v prid postopku z dodajanjem jagod med fermentacijo.
Ključne besede: 'Zelen' (Vitis Vinifera L.), alternativni pristopi v predelavi grozdja, krioekstrakcija, dodajanje sveţih jagod med alkoholno fermentacijo, proste aromatične spojine v vinu, vezane aromatične spojine v vinu, senzorika vina
Objavljeno v RUNG: 23.01.2017; Ogledov: 9619; Prenosov: 326
Celotno besedilo (1,16 MB)

Opis: Z odstranjevanjem listov v predelu grozdov se lahko spremeni mikroklima grozdov, ki lahko izzove spremembe v sekundarnem metabolizmu vinske trte, ki so odvisne tudi od časa izvedbe ukrepa. Uravnavanje sinteze aromatskih komponent je zanimivo pri belih sortah kot je sorta 'Sauvignon blanc', kjer so metoksipirazini in tioli tisti, ki oblikujejo značilno aromo vina te sorte. Eksperiment diplomske naloge smo zastavili na Oslavju (Gorica, Italija) v vinogradu sorte grozdja 'Sauvignon blanc' (Vitis vinifera L.). Želeli smo preveriti vpliva odstranjevanja listov v predelu grozdja pred in po cvetenju na količino in kakovost pridelka ter aromatske lastnosti grozdja in vina. Količinski parametri pridelka so pokazali majhne vplive izvedenih ukrepov razlistanja; pozno razlistanje na količino pridelka ni vplivalo, v nasprotju z razlistanjem pred cvetenjem, kjer smo opazili rahlo zmanjšanje pridelka po trsu in mase grozdov. Tudi pri osnovnih zrelostnih parametrih smo opazili manjše spremembe, predvsem večje vsebnosti topne suhe snovi pri razlistanju pred cvetenjem. Pri aromatskih komponentah smo zaznali vpliv razlistanja pred cvetenjem na količino prekurzorjev tiolov tako v grozdju kot tudi vinu; večjo vsebnost 4-merkapto-4-metilpentan-2-on (4MMP) in nižje koncentracije 3-merkaptoheksan-1-ol (3MH). S poznejšim odstranjevanjem listov smo zmanjšali koncentracije 4MMP, na vsebnost 3MH ta ukrep ni vplival. Tudi s senzorično oceno vina smo potrdili pomembne vplive razlistanja pred in po cvetenju na določene note v aromi vina 'Sauvignon blanc'. Leaf removal changes cluster microclimate, and thus modifications in the secondary metabolism are triggered, but differently as regard to the timing of application. In case of white grape varieties, the interest on the modification of aroma characteristics is searched, and in case of 'Sauvignon blanc', the shift in concentration of methoxypyrazines and thiols is responsible for the bouquet of the wines. An experimental trial was set up in Oslavia (Gorizia, Italy) with the aim to evaluate how pre-flowering and post-flowering leaf removal applied on 'Sauvignon blanc' vines could change the aromatic occurrence in grapes and wines. The yield parameters were slightly affected by the treatments of leaf removal; while late leaf removal did not impact on production, pre-flowering leaf removal slightly promoted a reduction on yield and cluster weight. Also basic maturation parameters were slightly changed, mainly higher soluble solids in case of pre-flowering leaf removal. As regard aromatics, both thiol precursors in grapes and thiols in wines revealed to be shifted in case of pre-flowering leaf removal, with higher values of 4-mercapto-4-methyl-pentan-2-one and lower values of 3-mercaptohexan-1-ol. In case of late leaf removal lower concentration of 4MMP were revealed and similar of 3MH. Also the degustation of the wines revealed some peculiarities of pre-flowering and late leaf removal treatments for some important sensorial notes of 'Sauvignon blanc' wines.
Ključne besede: Vitis vinifera L. cv. 'Sauvignon blanc', razlistanje pred cvetenjem, razlistanje po cvetenju, aromatske komponente, tioli, LC-MS Vitis vinifera L. cv. 'Sauvignon blanc', pre-flowering leaf removal, post-flowering leaf removal, aromatic compounds, thiols, LC-MS
Objavljeno v RUNG: 14.01.2016; Ogledov: 9568; Prenosov: 312
Celotno besedilo (1,30 MB)