Oenological Characteristics Research Articles

Effects of traditional and light pruning on viticultural and oenological performance of Bobal and Tempranillo vineyards

<p style="text-align: justify;"><strong>Aim</strong>: Light pruning may improve vine yield and quality although vineyard responses are variable. We assessed the effects of traditional manual pruning and mechanical light pruning on the viticultural and oenological performance of <em>Vitis vinifera </em>cv. Bobal and cv. Tempranillo.</p><p style="text-align: justify;"><strong>Methods and results</strong>: During 2008-2011, Bobal and Tempranillo vineyards underwent traditional pruning or light pruning. The effects of both pruning techniques were determined in vine vigour and yield, and grape and wine characteristics. Both cultivars responded similarly to the pruning techniques assayed: i) light-pruned plants tended to overcrop, ii) grape yield significantly increased with light pruning and produced more clusters with smaller berries, and iii) the oenological characteristics of grapes were slightly affected since fruit ripeness was delayed in mechanically light-pruned vineyards.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Mechanical light pruning <em>vs.</em> traditional manual pruning offers potential benefits: 30% higher yields; lower cluster and berry weights; a 40% reduction in pruning costs; and production of wines with lower alcohol while maintaining colour and phenolics.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: No detrimental effect of light pruning on grape characteristics was found, and the wines deriving from these grapevines offered good oenological characteristics. Mechanical light pruning may prove a suitable tool to prolong the vine vegetative cycle, which is reduced by the climate change in the Utiel-Requena region.</p>

POLYPHENOLIC POTENTIAL OF THE RARE CROATIAN CULTIVAR 'DOBRICIC' (VITIS VINIFERA L.)

Croatia is very rich in grapevine (Vitis vinifera L.) biodiversity and many native cultivars have been grown from ancient times, mostly along the Dalmatian coast. Many of the old native cultivars have almost vanished and ?Dobricic? is one of them. This cultivar has a great potential to be used in planting new vineyards, but its oenological characteristics still have not been defined and its wine is still not available on the Croatian market. Polyphenolic compounds are of profound significance for determining technological and nutritional values as well as sensory properties of grape cultivars and wines. In this work, the phenolic potential of ?Dobricic? grapes has been evaluated. Two different vineyards with this cultivar were considered. Three samples from each vineyard were taken at the time of harvest. Simulated maceration assays were carried out in model wine solutions containing 12% ethanol, 5 g/L of tartaric acid and 50 mg/L of SO2, neutralized with 0.3 M NaOH to pH=3.2 in order to investigate the composition of the polyphenols that were extracted from the grape into the wine. For each sample, separate extraction assays were performed using the grape skin and seeds. The results show that grape extract of this rare native cultivar contains appre-ciable amount of total phenols, proanthocyanidins and catechins as well as antho-cyanins. It was determined that grape skin is rich mainly in high-molecular-mass proanthocyanidins and anthocyanins. The skin contained higher concentration of low-molecular-mass proanthocyanidins than the seeds, as determined by vanillin index.

Selection and characterization of a Patagonian Pichia kudriavzevii for wine deacidification.

The purpose of this study was to select autochthonous yeasts with metabolic ability to degrade L-malic acid for its potential use in young wine deacidification. Fifty seven Patagonian nonSaccharomyces yeast of oenological origin were identified by conventional molecular methods and tested in their capability to grow at the expense of L-malic acid. Only four isolates belonging to Pichia kudriavzevii species showed this property, and one of them was selected to continue with the study. This isolate, named as P.kudriavzevii ÑNI15, was able to degrade L-malic acid in microvinifications, increasing the pH 0·2-0·3 units with a minimal effect on the acid structure of wine. Additionally, this isolate produced low levels of ethanol, important levels of glycerol (10·41±0·48gl(-1) ) and acceptable amounts of acetic acid (0·86±0·13gl(-1) ). In addition, it improved the sensorial attributes of wine increasing its fruity aroma. The selection of yeasts for oenological use among nonSaccharomyces species led to the finding of a yeast strain with novel and interesting oenological characteristics which could have significant implications in the production of well-balanced and more physicochemical and microbiological stable young wines. The use of P.kudriavzevii ÑNI15 as mixed starter with S.cerevisiae would eliminate the cultural and cellar operations undertaken to adjust the musts acidity, therefore improving wine quality and reducing production costs.

Reducing pesticide level in wine by selective filtration

Wine Pesticide residues, even when below grape regulatory limit, are a concern for consumers and have an impact on the export potential of wine in certain markets. A consortium of European SMEs (www.adfimax.com) has developed a product that reduces the level of mycotoxins and pesticides in wine while keeping all other wine parameter identical. The product is derived from renewable vegetable fiber. The production process includes both activation and micronisation. The usage recommendation is to substitute only the pre-coat, typically perlite, by the product at 1 or 1.5 kg⋅m−2 without changing the other layer (body feed) typically kieselguhr . This paper describes the results of numerous industrial trials that were performed in France, Luxemburg, Germany and Spain. The impact of the product on the wine oenological characteristics was evaluated for different wine (white, red and rose ) in different countries and for different grape variety (including Cabernet sauvignon, Merlot and Gamay). Results showed a reduction of the test wine pesticide level of 50% to 60% for all pesticides compared to the blank. Level of pesticide analyzed in the cake where extremely high at a level of a 1,000 times greater than the filtered wine showing the ability of the product to selectively capture the pesticides molecules.

Production of aroma compounds by cryotolerantSaccharomycesspecies and hybrids at low and moderate fermentation temperatures

Among the most important factors influencing wine quality are yeast strains and fermentation temperature. Fermentation at low temperature is presently used in winemaking to improve both aroma formation and retention. In this study, we have analysed the oenological characteristics of Tempranillo wines produced at 12 and 28°C by different Saccharomyces species and hybrids. Low temperature had a strong influence on yeasts fermentation kinetics, increasing fermentation times to more than 2 weeks. In some strains, glycerol production seemed to be positively influenced by low fermentation temperature. Analysis of the aroma composition of wines produced by different Saccharomyces species and hybrids revealed large differences depending on fermentation temperature. Higher alcohols production seemed to be dependent on the strain. Production of acetate esters seemed to be favoured at 28°C, whereas production of ethyl esters was apparently preferred at low fermentation temperatures. The best aroma producers at 28°C were Saccharomyces cerevisiae strains, whereas Saccharomyces uvarum and some hybrids excelled at 12°C. Our results suggest that fermentation temperature and yeast species are of crucial importance for production of metabolites influencing wine aroma.

Ampelographic and oenological characterization of the ancient grapevine cv. Dobričić grown in the coastal region of Croatia

<p style="text-align: justify;"><strong>Aims</strong>:A four-year study (2007 through 2010) was carried out to determine agronomic, biological, and oenological characteristics of Dobričić grapevines so as to evaluate this cultivar and protect it from extinction.</p><p style="text-align: justify;"><strong>Methods and results</strong>: 38 characteristics from the OIV descriptor list were used to describe young shoot, mature leaf, cluster, and berry morphology of Dobričić grapevines. The dimensions of an average leaf were constructed from measured leaf variables. A typical Dobričić genotype at nine microsatellite loci is presented. ELISA analysis revealed high virus incidence and all samples tested were GLRaV-3 positive. The profile of different classes of polyphenols in Dobričić wine was determined using HPLC and spectrophotometry. The concentrations of polyphenols in Dobričić wine, especially anthocyanins, hydroxycinnamic acids and stilbenes, were high compared to major red wines reported in the literature. Descriptive sensory analysis was carried out to determine the aroma attributes describing a Dobričić monovarietal wine.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Knowledge of the biodiversity of the grapevine cultivars of Croatia is still scant. This study provides for the first time ampelographic and oenological information on Dobričić grapevines and demonstrates its high quality potential.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The results of the ampelographic characterization would be helpful in the identification and selection of Dobričić for cultivation in certain vine-growing areas. The outstanding quality of Dobričić makes it very promising for wine blending (colour improvement) and plant breeding purposes.</p>

Quantification and characterization of cell wall polysaccharides released by non-Saccharomyces yeast strains during alcoholic fermentation

In order to improve knowledge about the oenological characteristics of non-Saccharomyces yeast strains, and to reconsider their contribution to wine quality, we studied the release of polysaccharides by 13 non-Saccharomyces strains of different species (three wine yeasts, six grape yeasts, and three spoilage yeasts) during alcoholic fermentation in synthetic must. Three Saccharomyces cerevisiae strains were included for comparison. All of the non-Saccharomyces strains released polysaccharides into fermentation medium; the amount released depended on the yeast species, the number of cells formed and their physiological conditions. Normalizing the quantity of macromolecules released to the cell biomass revealed that most non-Saccharomyces strains produced a greater quantity of polysaccharides compared to S. cerevisiae strains after 7 and 14days of fermentation. This capacity was particularly expressed in the studied wine spoilage yeasts (Saccharomycodes ludwigii, Zygosaccharomyces bailii, and Brettanomyces bruxellensis). Chemical characterization of exocellular polysaccharides produced by non-Saccharomyces yeasts revealed them to essentially be mannoproteins with high mannose contents, ranging from 93% for S'codes. ludwigii to 73–74% for Pichia anomala and Starmerella bombicola. Protein contents varied from 9% for P. anomala to 29% for Z. bailii. These compositions were very similar to those of the S. cerevisiae strains, and to the chemical composition of the cell wall mannoproteins of different yeast species. The presence of galactose, in addition to mannose and glucose, in the exocellular polysaccharides released by Schizosaccharomyces pombe, confirmed the parietal nature of the polysaccharides released by non-Saccharomyces yeasts; only this species has a galactomannan located in the outer layer of the cell wall.

Evolution-based strategy to generate non-genetically modified organisms Saccharomyces cerevisiae strains impaired in sulfate assimilation pathway

An evolution-based strategy was designed to screen novel yeast strains impaired in sulfate assimilation. Specifically, molybdate and chromate resistance was used as selectable phenotype to select sulfate permease-deficient variants that unable to produce sulfites and hydrogen sulfide (H(2) S). Four Saccharomyces cerevisiae parent strains were induced to sporulate. After tetrad digestion, spore suspensions were observed under the microscope to monitor the conjugation of gametes. Then, the cell suspension was inoculated in tubes containing YPD medium supplemented with ammonium molybdate or potassium chromate. Forty-four resistant strains were obtained and then tested in microvinifications. Three strains with a low sulfite production (SO2 < 10 mg l(-1)) and with an impaired H2S production in grape must without added sulfites were selected. Our strategy enabled the selection of improved yeasts with desired oenological characteristics. Particularly, resistance to toxic analogues of sulfate allowed us to detect strains that unable to assimilate sulfates. This strategy that combines the sexual recombination of spores and application of a specific selective pressure provides a rapid screening method to generate genetic variants and select improved wine yeast strains with an impaired metabolism regarding the production of sulfites and H2S.

Outlining a future for non-Saccharomyces yeasts: Selection of putative spoilage wine strains to be used in association with Saccharomyces cerevisiae for grape juice fermentation

The use of non-Saccharomyces yeasts that are generally considered as spoilage yeasts, in association with Saccharomyces cerevisiae for grape must fermentation was here evaluated. Analysis of the main oenological characteristics of pure cultures of 55 yeasts belonging to the genera Hanseniaspora, Pichia, Saccharomycodes and Zygosaccharomyces revealed wide biodiversity within each genus. Moreover, many of these non-Saccharomyces strains had interesting oenological properties in terms of fermentation purity, and ethanol and secondary metabolite production. The use of four non-Saccharomyces yeasts (one per genus) in mixed cultures with a commercial S. cerevisiae strain at different S. cerevisiae/non-Saccharomyces inoculum ratios was investigated. This revealed that most of the compounds normally produced at high concentrations by pure cultures of non-Saccharomyces, and which are considered detrimental to wine quality, do not reach threshold taste levels in these mixed fermentations. On the other hand, the analytical profiles of the wines produced by these mixed cultures indicated that depending on the yeast species and the S. cerevisiae/non-Saccharomyces inoculum ratio, these non-Saccharomyces yeasts can be used to increase production of polysaccharides and to modulate the final concentrations of acetic acid and volatile compounds, such as ethyl acetate, phenyl-ethyl acetate, 2-phenyl ethanol, and 2-methyl 1-butanol.

Characterization of α-rhamnosidase activity from a Patagonian Pichia guilliermondii wine strain

The purpose of this study was to characterize the α-l-rhamnosidase of Pichia guilliermondii NPCC1053 indigenous wine strain from North-Patagonian region. The optimization of yeast culture conditions was carried out and the effects of oenological parameters on α-l-rhamnosidase activity were evaluated. Additionally, the effect of direct contact with must and wine on α-l-rhamnosidase activity was assayed. This strain showed an intracellular inducible α-l-rhamnosidase activity. This enzyme was active at pH, glucose and SO(2) concentrations usually found at the beginning of the fermentation as well as retained high levels of activity after 24 h of incubation in must. Furthermore, P. guilliermondiiα-l-rhamnosidase was able to release monoterpenols and alcohols from grape glycosidic extracts. The α-l-rhamnosidase belonging to P. guilliermondii indigenous wine yeast strain showed mainly an intracellular location and evidenced interesting oenological characteristics. This study contributes to the knowledge of α-l-rhamnosidases from yeast origin because at present, there are few reports about this enzymatic activity in these micro-organisms. In addition, this work is relevant to the regional wine industry considering that this enzyme could be used in the production of more aromatic young wines.

Identification of yeast population dynamics of spontaneous fermentation in Beijing wine region, China

The aim of this study was (i) to investigate changes occurring in the yeast population profile during spontaneous fermentation of grape juice; (ii) to assess the proliferation of commercial yeast starter culture strains in vineyards; and (iii) to identify indigenous wine strains for future development of starter strains that better reflect the yeast biodiversity of China’s grape-growing regions. To achieve this, yeasts were isolated at four different stages during fermentation of both hand-pressed and winery-sourced must samples ofVitis vinifera L. cv. Roussanne and Merlot. A total of 1600 yeast colonies were isolated and then grouped according to macroscopic and microscopic characteristics. A selection of 291 colonies from the different groups was subjected to species identification using the internal transcribed spacer regions of the 5.8S rRNA gene (ITS1-5.8S-ITS2 region) and the inter-delta (δ) sequence of the 26S rRNA D1/D2 region. In addition, 104Saccharomyces cerevisiae colonies were subjected to strain identification. Twelve species belonging to nine different genera were found amongst the isolates. During the early stages of fermentation, it was found thatHanseniaspora uvarum andCandida stellata numerically dominated the four to six yeast species present, including a region-specific yeast,Sporobolomyces beijingensis. TwoS. cerevisiae strains were isolated from the final stage of fermentation. These two indigenous strains, which were found to be different from the nine commercial yeast strains previously used as starter cultures in this particular Beijing-based winery, might possess potentially important region-specific oenological characteristics. This study provides the first essential step towards the preservation and exploitation of the hidden oenological potential of the untapped wealth of yeast biodiversity in China’s wine-producing regions.

Effect of phenolic acids on glucose and organic acid metabolism by lactic acid bacteria from wine

The influence of phenolic ( p-coumaric, caffeic, ferulic, gallic and protocatechuic) acids on glucose and organic acid metabolism by two strains of wine lactic acid bacteria ( Oenococcus oeni VF and Lactobacillus hilgardii 5) was investigated. Cultures were grown in modified MRS medium supplemented with different phenolic acids. Cellular growth was monitored and metabolite concentrations were determined by HPLC-RI. Despite the strong inhibitory effect of most tested phenolic acids on the growth of O. oeni VF, the malolactic activity of this strain was not considerably affected by these compounds. While less affected in its growth, the capacity of L. hilgardii 5 to degrade malic acid was clearly diminished. Except for gallic acid, the addition of phenolic acids delayed the metabolism of glucose and citric acid in both strains tested. It was also found that the presence of hydroxycinnamic acids ( p-coumaric, caffeic and ferulic) increased the yield of lactic and acetic acid production from glucose by O. oeni VF and not by L. hilgardii 5. The results show that important oenological characteristics of wine lactic acid bacteria, such as the malolactic activity and the production of volatile organic acids, may be differently affected by the presence of phenolic acids, depending on the bacterial species or strain.

Selection and preliminary characterization of β-glycosidases producer Patagonian wild yeasts

Four pre-selected indigenous yeast strains belonging to Candida guilliermondii (V 2 and V 5), Candida pulcherrima (V 6) and Kloeckera apiculata (V 9), were used as β-glucosidase (βGL) and β-xylosidase (βXL) sources. The optimization of yeast culture conditions was carried out and the effects of oenological parameters on β-glycosidase activities were evaluated. C. guilliermondii V 2 and C. pulcherrima V 6 strains were selected. These strains showed intracellular ( C. pulcherrima V 6) and parietal ( C. guilliermondii V 2) constitutive βGL and βXL. The enzymatic activities were active at pH, glucose, ethanol and SO 2 concentrations usually found in winemaking and they were able to release monoterpenols and alcohols from grape juice glycoside extracts. Additionally, these yeast strains were not able to produce volatile acidity and off flavour. Regional ecological relevance of these species was also discussed. Our results evidence that the selected C. guilliermondii V 2 and C. pulcherrima V 6 strains have interesting oenological characteristics and allow us to think in their potential application in winemaking.

Selection of indigenous Saccharomyces cerevisiae strains according to their oenological characteristics and vinification results

Xynomavro and Muscat Hamburg grapes were fermented spontaneously, producing red and white wine, respectively. The indigenous yeast flora, isolated at three phases of these fermentations, was studied. One hundred and ten strains were isolated, eighty-four of which were identified as Saccharomyces cerevisiae. Six of these strains were selected for their satisfactory oenological properties to be tested as starters in wine fermentations. The quality of the produced wines was evaluated after determination of their aromatic compounds and sensory analysis. S. cerevisiae strain BT4, as well as the AM4+BM3 combination, were considered the best as they produced wines characterized by fruity aromas and were highly accepted among panelists.

Molecular and technological approaches to evaluate strain biodiversity in Hanseniaspora uvarum of wine origin

The characterization by molecular and physiological methods of wild apiculate strains, isolated from 'Aglianico del Vulture' grape must. The restriction analysis of 18S rDNA allowed the identification of strains at the species level, which were predominantly Hanseniaspora uvarum. The RAPD analysis and the evaluation of technological traits, such as the metabolic and enzymatic activities, were useful to evaluate the polymorphism of this species. The RAPD analysis clustered the wild H. uvarum strains in four main genetic groups and a very high phenotypic variability confirmed this genetic polymorphism. The technological variables, which determined the strain biodiversity differed significantly, demonstrating that these technological traits are strain dependent. A certain correlation was found between the strain behaviour and its isolation zone, indicating the influence of the environment on the genetic patrimony of the population. The genetic and technological biodiversity recorded among H. uvarum wild strains represents the basis for organizing a collection of apiculate strains exhibiting oenological characteristics at different levels, such as high/low production of secondary compounds, and, therefore, potentially useful for a selection programme.

Screening and typing of Patagonian wine yeasts for glycosidase activities.

The purpose of this study was to select autochthonous glycosidase producer yeasts with potential use in industrial production of Patagonian red wines. The study was carried out in oenological autochthonous yeasts from Comahue region (Argentinean North Patagonia). A set of screenable yeast phenotypic characteristics indicative of their potential usefulness in more aromatic red wine production was defined and tested in both, Saccharomyces and non-Saccharomyces populations. Twelve isolates showing six different glycosidase phenotypes were selected and they were characterized at species and strain levels using molecular methods. A close correlation between molecular and phenotypic characteristics was observed. Five strains belonging to Candida guilliermondii, C. pulcherrima and Kloeckera apiculata with highest constitutive beta-glucosidase activity levels without anthocyanase activity were discriminated. Some of them also showed constitutive beta-xylosidase and inductive alpha-rhamnosidase activities. The extension of the selection of oenological yeast to non-Saccharomyces species provided strains possessing novel and interesting oenological characteristics which could have significant implications in the production of more aromatic young red wine. As these non-Saccharomyces are indigenous to wine, they can be used in mixed starters at the beginning or as pure cultures at the end fermentation to contribute in enhancing the wine nuance that is typical of this specific area.

Identification and characterization of Saccharomyces cerevisiae and Saccharomyces paradoxus strains isolated from Croatian vineyards.

The identification, differentiation and characterization of indigenous Saccharomyces sensu stricto strains isolated from Croatian vineyards and the evaluation of their oenological potential. A total of 47 Saccharomyces sensu stricto strains were isolated from Chardonnay grapes and identified by physiological and molecular genetic methods. By using the standard physiological and biochemical tests, six isolates were identified as Saccharomyces cerevisiae and 41 as Saccharomyces paradoxus. However, PCR-RFLP analyses of the internal transcribed spacer (ITS1) region of the 18S ribosomal DNA identified 12 of the isolates as S.cerevisiae and 35 as S. paradoxus. Fermentation trials in a grape juice medium showed that these isolates ferment vigorously at 18 degrees C and display tolerance to high levels of ethanol. None of these isolates appeared to produce either hydrogen sulphide or killer toxins. Saccharomyces paradoxus, possessing potentially important oenological characteristics, occurs in much higher numbers than S. cerevisiae in the indigenous population of Saccharomyces sensu stricto strains in Croatian vineyards. This study forms an essential step towards the preservation and exploitation of the hidden oenological potential of the untapped wealth of yeast biodiversity in the Croatian grape-growing regions. The results obtained demonstrate the value of using molecular genetic methods, such as PCR-RFLP analyses, in conjunction with the traditional taxonomic methods based on phenotypic characteristics in such ecotaxonomic surveys. The results also shed some light on the ecology and oenological potential of S.paradoxus, which is considered to be the natural parent species of the domesticated species of the Saccharomyces sensu stricto group.

Study of the oenological characteristicsand enzymatic activities of wine yeasts

Seventy-four wine strains of theSaccharomycesgenus were tested to study their oenological characteristics and enzymatic activities. These strains were isolated from spontaneous microbiota taken from cellars in the Valdepeñas region (Spain) and identified by contour homogeneous electric field (CHEF) technique. When Cluster Analysis was applied to oenological properties, only SH2production, tolerance to 120of ethanol and synthesis of killer toxin contributed to the distribution of the strains in the different statistical groups. All the strains possessed esterase activity and some also showed protease and pectinase activities. None of them hadβ-D-glucosidase activity.

The oenological characteristics of commercial dry yeasts

Twenty preparations of dry active yeast (18 Saccharomyces cerevisiae and two Saccharomyces bayanus) available in Italy were tested in white and red musts (Moscato, Albana and Sangiovese) to study their oenological characteristics (i.e. fermentation rate, total alcohol and acetic acid production). After the application of chemiometric techniques for descriptive analyses to the results of the oenological assessment, the yeasts were divided into three groups A, B and C. Group A had some strains which caused low values of dry extract and glycerol in wines. Yeasts in group B were less interesting in terms of their oenological characteristics. Yeasts in group C had mixed behaviour with positive and negative characteristics and their utilisation must be considered separately each time. The research has shown that technological investigation is necessary after a correct selection of yeasts to limit the number of strains for subsequent study, and to characterise suitable strains for different oenological practices.

Expression in a wine yeast strain of the Aspergillus niger abfB gene

A recombinant wine yeast strain has been constructed expressing the gene coding for a-L-arabinofuranosidase B from Aspergillus niger under the control of the yeast actin gene promoter. The protein is efficiently secreted by the recombinant yeast, allowing its purification and characterisation. The heterologous α- l-arabinofuranosidase B shows similar physico-chemical properties to the native enzyme. The wine produced in microvinification experiments using the recombinant yeast presents the same oenological characteristics as obtained with the untransformed strain. The a-L-arabinofuranosidase B protein is detected throughout the fermentation.