Seven indigenous yeast strains of Saccharomyces paradoxus previously isolated and identified using molecular and physiological methods were tested for their fermentation abilities. Chemical analyses ...of produced wines showed differences compared with the Saccharomyces cerevisiae strain used as a control. The examined S. paradoxus strains showed good fermentation vigour, ethanol tolerance and difference in the fermentation rate. Four of seven analysed S. paradoxus strains (RO66, RO54, RO11 and RO134) metabolised sugar up to 1 g L⁻¹. The total amount of higher alcohol was lower compared with S. cerevisiae wines. Strain RO83 was able to degrade up to 40% malic acid and can be used for biological deacidification. Sensory evaluation of dry and semidry wines underlined good enological properties and positive influence of tested wine strains on final wine quality. All these properties of S. paradoxus strains pointed out the possibility of their application in wine industry.
During a two-year study, the effect of different grape mash maceration treatments (skin contact at 20 degree C for 10, 20 and 30 h) and cryomaceration (skin contact at 7 degree C for 10, 20 and 30 h) ...on the concentration of free and bound monoterpenes and total phenols in Malvazija istarska wine (the most spread white wine variety in Istria) was monitored. Monoterpenic alcohols linalool, alpha -terpineol, citronellol, nerol and geraniol were determined by gas chromatography after isolation on octadecylsilica (C sub(18)) sorbent and elution with pentane/dichlorometane ratio of 2:1, while total phenols were determined spectrophotometrically with Folin-Ciocalteau reagent. Sensory evaluation of wines was performed using the Buxbaum method. The obtained results show that linalool and geraniol are the most abundant monoterpenes in Malvazija istarska, and that grape mash maceration treatments cause significant increase of free and bound monoterpene concentrations compared to those in control treatment wine obtained without maceration. The content of phenols, which are subject to oxidation, was found to be significantly lower in wines produced by cryomaceration treatments, while in those produced by maceration at 20 degree C the concentration of total phenols increased proportionally with the duration of maceration, negatively influencing wine quality by causing higher colour intensity and bitter taste.
The aim of this work was to study the infl uence of 8 autochthonous yeasts strains on the sulfur dioxide formation. For this purpose grape must from the Traminer, Muller Turgau and Chardonnay grapes ...was used. Yeast strains used were cultivated at the Department for Microbiology, Faculty of Agriculture, University of Zagreb. Five of them were H2S negative and three H2S positive. Tested yeast strains produced from 19 up to 45 mg/l of sulfur dioxide. The highest sulfur dioxide producer was one of the H2S positive yeast strains. The results indicated the initial sugar concentration to be very important for the ratio of sulfur dioxide production. Yeasts were more effi cient at higher sugar levels.
The effect of malolactic fermentation (MLF) on the volatile composition of white wines made from autochtonous grape variety Kraljevina was studied by inoculation with selected lactic acid bacteria. ...At the end of malolactic fermentation, after the decomposition of the malic acid present in wine the non volatile compounds were analyzed by HPLC, while volatile compounds were analyzed by gas chromatography. All wines were also sensory analyzed. Results showed changes in acetaldehyde, some higher alcohols, ethyl esters, free and bound monoterpenes and some organic acids that contribute to enhance the sensory properties and quality of Kraljevina wines that underwent malolactic fermentation.
Changes in some aroma compounds and sensory properties caused by different commercial S. cerevisiae strains and by epiphyte microorganisms in Chardonnay wines were investigated. Wines fermented with ...the Lalvin-71 B strain contained significantly lower concentrations of alcohol, isoamyl alcohol, isobutanol and total acidity than the wines obtained from spontaneous and other inoculated fermentations. The highest concentrations of 2-phenyl ethanol and 2-phenyl ethyl acetate were found in the spontaneously fermented wines, whereas no essential changes in these compounds were found among the wines of other treatments. Compared to the spontaneous fermentation, Lalvin-71 B strain fermented wines had somewhat higher concentrations of butyric and caproic acid and ethyl butyrate. Lalvin-71 B strain fermented wines were assessed as the best whereas the quality of the wines produced with Lalvin aromatic-2056 strain was the most inferior in quality.
Tartaric and malic acids are essential constituents of grape must and wine, contributing directly to its taste as well as balancing with other flavors. High temperature conditions during maturation ...time can strongly affect malic acid/tartaric acid ratio resulting in a lower acid content due to increasing degradation of malic acid. In the 2006 year Chardonnay grape (clone SMA 130, CL 95, CL96, CL548, SMA 123, R8, VCR10) from Zagreb wine region was collected every 3-5 days from the moment of verasion until the harvest time. The smallest malic acid/tartaric acid ratio was detected in CL 95 clone while clone CL 96 and VCR10 had the highest malic acid/tartaric acid ratio. There was no difference in the citric acid content among tested clones.
Changes in chemical composition and sensory properties caused by chemical and microbiological methods of deacidification in Moslavac (syn. Furmint) wines were investigated. Alcoholic fermentation of ...Moslavac musts was carried out with two different strains of the yeasts Saccharomyces paradoxus. There were no marked differences in chemical composition among the wines. Compared to the control microbiological deacidification of wines by Oenococcus oeni resulted in a complete decomposition of malic acid, total acidity decrease of 1.55 g/L and pH value increase of 0.14 units. There were no significant differences in volatile acidity, tartaric and citric acid concentrations between the control and malolactically fermented wine. Chemically deacidified wines contained similar total acidity but higher pH values than malolactically fermented wines. Compared to control wines, the tartaric acid concentration decrease of 2.13 g/L and the pH value increase of 0.5 units were determined. The sensory quality of Moslavac wines of high acidity was improved by the applification of deacidification methods. Chemically deacidified wines were assessed as the best whereas the quality of the control wines was judged inferior.
'Zilavka' is the autochthonous white grape variety of Herzegovina and there is a great interest of local winemakers to produce 'Zilavka' wines, which are characterised with a fine balance between the ...fermentation bouquet and grape-based aromas. The fermentation temperatures of some wineries in Herzegovina often can exceed 30 degree C what results with inferior overall wine quality. In this research changes in concentration of higher alcohols and sensory properties caused by fermentation at different temperatures in 'Zilavka' wines were investigated. Compared to fermentation at the temperature above 26 degree C, fermentation at 15 degree C and 20 degree C caused significant decrease in the concentration of total higher alcohols and individual isoamyl alcohol and isobutanol only in one year of the research. There were no differences in concentration of 1-propanol and ethyl acetate among all tested wines in both years. The best sensory evaluated were the wines fermented at 20 degree C, while the wines produced at the temperature above 25 degree C were of the most inferior quality.
Controlling skin contact conditions is vital to obtain high quality white wines and it has become a standard procedure in many white wine-production areas. The aim of this work was to investigate the ...changes in composition and sensory properties of Žilavka wines obtained with different cold skin contact time. Results indicate that cold maceration positively influence the quality of Žilavka wines. The results pointed out significant increase in dry extract, ash, total phenol and decrease in tartaric acid and higher alcohol content in Žilavka wines obtained by 10 or 20 hours cold maceration period. Best organoleptic quality of Žilavka wines was obtained by cold maceration at 10 °C during 20 hours period.
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