Aims
Twenty‐five enological yeasts belonging to nine different species (Candida zeylanoides, Cryptococcus uzbekistanensis, Debaryomyces hansenii, Lachancea thermotolerans, Metschnikowia pulcherrima, ...Torulaspora delbrueckii, Williopsis pratensis, Zygosaccharomyces bailii and Saccharomyces cerevisiae) were screened for aroma formation and fermentative behaviour as part of a non‐Saccharomyces yeast selection programme.
Methods and Results
Pure cultures were inoculated in pasteurized grape juice in order to perform alcoholic fermentations. Some non‐Saccharomyces species did not ferment, others did not get established and none of them completed alcoholic fermentations. The physico‐chemical parameters of the wines and the abundance of aromatic compounds at the end of alcoholic fermentation highlighted the notable differences in the aroma‐forming ability and fermentative behaviour of the different non‐Saccharomyces species, but not within clones.
Conclusions
Lower diversity was detected within non‐Saccharomyces species than that reported in S. cerevisiae with regard to enological behaviour and aromatic profiles. Metschnikowia pulcherrima and L. thermotolerans are the two species with higher possibilities to become an inoculum.
Significance and Impact of the Study
Few significant differences were found within clones of the same species, but very important parameters in wine quality, such as volatile acidity, ethyl acetate and acetoin, which would justify selection programmes within those species. The results also demonstrated that T. delbrueckii and L. thermotolerans are two close species in their aromatic profiles.
•Foliar application of urea and phenylalanine modified grape phenolic content.•Anthocyanins and flavonols were the phenolic compounds most affected by the foliar treatments.•In general, application ...of urea and phenylalanine improved grape quality.•These practices may help to obtain grapes of higher quality.
Grapevines may require the input of nitrogen to grow and to guarantee an appropriate grape composition. Recently there has been a growing interest in foliar fertilization, which entails a fast and efficient assimilation of the products. The aim of this work was to study the influence of foliar applications of phenylalanine and urea, at two different doses, on grape anthocyanins, flavonols, flavan-3-ols, phenolic acids, and stilbenes. All treatments were applied at veraison and one week later at doses of 0.9 and 1.5kgN/ha. The results showed that the synthesis of phenolic compounds was favoured by foliar applications of phenylalanine and urea. The application of the lowest dose of urea was the most effective treatment, increasing the content of several anthocyanins and flavonols. Moreover, none of the foliar treatments worsened the grape phenolic composition. In conclusion, foliar application of phenylalanine and especially urea, could be an interesting management tool for improving grape quality and their health-promoting properties.
•Effect of different nitrogen foliar treatments to vineyard on grape amino acid content.•Proline treatment did not affect the must nitrogen composition.•Phenylalanine and urea applications favoured ...the synthesis of the most amino acids.•Regardless of the formulation, nitrogen fertilizers improved grape amino acid content.•Enological interest to enhance amino acid content and a tool to improve wine quality.
The aim of this work was to study the influence of foliar application of different nitrogen sources on grape amino acid content. The nitrogen sources applied to Tempranillo grapevines were proline, phenylalanine, urea, and two commercial nitrogen fertilisers, both without and with amino acids in their formulations. All treatments were applied at veraison and one week later. Proline treatment did not affect the must nitrogen composition. However, phenylalanine and urea foliar application enhanced the plants’ synthesis of most of the amino acids, producing similar effects. In addition, the spray of commercial nitrogen fertilisers over leaves also induced a rise in grape amino acid concentrations regardless of the presence or absence of amino acids in their formulation. The most effective treatments were phenylalanine and urea followed by nitrogen fertilisers. This finding is of oenological interest for improved must nitrogen composition, ensuring better fermentation kinetics and most likely enhancing wine quality.
Aims
To determine the intraspecific genetic diversity within five non‐Saccharomyces yeast species and the diversity in phenotypic characteristic related to their technological properties.
Methods and ...Results
Seventy‐one non‐Saccharomyces yeasts isolated from different fermentations and facilities of the DOCa Rioja (Spain) belonging to five different wine species (Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, Zygosaccharomyces bailii and Williopsis pratensis) were subjected to clonal characterization by RAPD‐PCR, which evidenced wide diversity between them. They were also submitted to a screening for some oenological traits related to the improvement of the aroma of the wine and yeast development in musts. Strains within the same species showed different enzyme activities, tolerated different levels of SO2 and possessed different killer phenotypes. These characteristics made them adjust better or worse to specific vinification processes or wine quality criteria.
Conclusions
A significant genetic and phenotypic variation within the non‐Saccharomyces species studied was found, which makes necessary to carry out a selection process in each one.
Significance and Impact of the Study
Williopsis pratensis, a species that has not been thoroughly explored, may deserve further consideration for oenological applications. Due to the wide range of variation within species, the strains adaptation to the SO2 levels in musts has to be taken into account in selection processes.
In this work the influence of the foliar application of proline, phenylalanine, urea and two commercial nitrogen fertilizers, with and without amino acids, on grape aroma composition was studied. The ...treatments were applied in a Tempranillo vineyard, at a dose of total N of 900 g/ha, at veraison and a week later. Enological parameters and volatile compound content were determined in grapes. The results showed that terpenoids synthesis decreased with all treatments carried out in the vineyard, and there were not significant differences either in the amount of C13 norisoprenoids or in esters between treated and control samples. The treatment with phenylalanine increased the presence of benzenoid compounds and decreased C6 compounds. Therefore, this treatment could be considered the best from the point of view of grape aroma composition. The treatments with the commercial nitrogen fertilizers did not affect the total compound content present in the samples.
•Influence of nitrogen foliar application to vineyard on grape volatile composition.•Proline, phenylalanine, urea, and two nitrogen fertilizers were sprayed over leaves.•The vine was able to convert phenylalanine into 2-phenylethanol and 2-phenylethanal•Phenylalanine treatment was the best nitrogen application for aromatic composition.
BACKGROUND AND AIMS: The antiseptic effect of the addition of colloidal silver (CAgC) alone or in combination with a small quantity of sulfur dioxide (SO₂) was examined in both vinification and ...storage of red wines. METHODS AND RESULTS: Four treatments of grapes and wines with SO₂ and CAgC alone or in combination with a small quantity of SO₂ were established. All treatments of grapes provided similar control of yeast and lactic acid bacteria, however, the three treatments with CAgC were more effective in the control of acetic acid bacteria. The addition of CAgC did not affect fermentation, and the wines had physicochemical, aromatic and sensory characteristics similar to that of the control, but a lower alcohol content. None of the treatments maintained control of bacteria during storage. After 1 month of stabilisation and 4 months of storage, the wines produced with CAgC had a higher colour intensity and a lower concentration of both anthocyanins and total polyphenols. Moreover, the final wines showed little difference in volatile and biogenic amine composition, which affected neither their quality nor their sensory characteristics. CONCLUSIONS: Under the conditions studied, addition of SO₂ could be reduced or replaced by CAgC. Overall, wines elaborated with CAgC showed no microbiological problems, and moreover, they had a higher colour intensity and similar aromatic composition and biogenic amines concentration to that of the control; their sensory characteristics were well rated. SIGNIFICANCE OF THE STUDY: Colloidal silver could be a promising antiseptic in the elaboration and storage of young wines.
The aim of this work was to study the influence of pulsed electric field (PEF) treatments on the volatile composition of three grape varieties. In order to do this, grapes were crushed and destemmed, ...and four PEF treatments were applied. The process was carried out continuously using a semi-industrial equipment. Volatile compounds were analyzed by SPME-GC–MS. The results showed that the effect of PEF treatment was different depending on variety. However, the aromatic profile of the studied varieties was not affected in any case. PEF enhanced the aromatic composition of Grenache, increasing the quantity of monoterpenoids. Moreover, a positive effect was observed in the amount of β-ionone, total esters and benzenoid compounds, and little difference was observed between treatments for C6 compounds. However, the volatile composition of Tempranillo and Graciano was not favored by PEF. In conclusion, from the point of view of the volatile composition and taking into account the treatments used in this study, it can be concluded that PEF is an appropriate technology to improve the aromatic quality of Grenache variety.
Pulsed electric field is a non-thermal technology that enhances the volatile content in Grenache. Consequently, this technology could be used in the food industry to improve the aromatic quality of Grenache must and therefore the overall quality of Grenache wine, as this variety is one of the most widely grown in the world.
•The effect of 4 continuous PEF treatments on grape volatile composition was assayed.•The influence of PEF treatments on volatile composition depended on grape variety.•PEF technology enhanced the volatile composition of Grenache grape variety.•However, volatile composition of Graciano and Tempranillo varieties did not improve.•PEF extraction was not selective as flavor profile of grape varieties did not change.
Brettanomyces bruxellensis is a major cause of wine spoilage due to the production of ethyl phenols, and it has become a major worldwide oenological concern in recent years. The most critical factor ...in volatile phenol production is the presence of microorganisms responsible for biosynthesis. In this work, carried out during three consecutive harvests, grapes and the first step in grape processing (stemming–crushing) have been evaluated as the origin of wine contamination by these spoilage yeasts. Results showed that there was nil or minimal presence of Brettanomyces yeasts in grapes and on the stemmer, in levels that the method was not able to detect. This shows that the main contamination of wines by this microorganism occurs in later stages of the vinification process and/or during storage. The contamination of many wines with Brettanomyces, either via the fruit or from the winery environment, during the early stages of vinification and before the start of aging, was confirmed by analyzing 100 recently made red wines, in which this yeast was detected in a high percentage of wines (27 %). However, the level of Brettanomyces yeasts found in the samples was low, with values which would not be sufficient to cause organoleptic defects. Consequently, this study confirms that many wines are still tainted by Brettanomyces when the winemaking phase comes to an end. It was also found that wines with problems during fermentation had a higher level of Brettanomyces. This is why it is essential to ensure strict controls during fermentation processes and conservation to prevent wine becoming spoiled or tainted.
Most common bacterial sepsis associated with transfusion is caused by contaminated Platelet Concentrates (PC). The screening of PC to detect bacterial contamination is obligatory in Mexico, and it is ...carried out in quality control programs. In Mexico, the identification and molecular characterization of bacterial contaminants to detect contamination sources have not been implemented due to high costs; however, it is an actual current need.
One hundred PC were randomly selected and microbiologically analyzed. This sample size corresponds to 1% of the PC obtained by the National Center of Blood Transfusion (NCBT) in Mexico City according to the Official Mexican Standard NOM-253-SSA1-2012. Additionally, molecular biology tests were implemented in order to identify the possible contamination sources.
Nine of the 100 PC analyzed (9%) showed bacterial contamination; analysis of the nucleotide sequences revealed the presence of characteristic microbiota from donor skin and soil. Diverse clonal relationship between the strains was identified in Staphylococcus epidermidis.
Detection of contaminants associated with environmental and skin flora, shows the need to implement measures in the process of disinfecting skin at the site of phlebotomy and cleaning each of the areas involved in blood collection.
La plus commune septicité bactérienne associée à la transfusion est causée par des concentrés plaquettaires contaminés (CP). Le dépistage de CP pour détecter la contamination bactérienne est obligatoire au Mexique et il est effectué dans des programmes de contrôle de qualité. L’identification et la caractérisation moléculaire des polluants bactériens pour détecter les sources de contamination n’ont pas été mises en œuvre au Mexique, à cause des hauts coûts; cependant c’est un besoin actuel réel.
Cent CP ont été aléatoirement choisis et microbiologiquement analysés. Cette taille de l’échantillon correspond à 1 % des CP obtenus du Centre national de transfusion de sang (NCBT) au Mexique, d’après la Norme officielle mexicaine NOM-253-SSA1-2012. Également, des tests de biologie moléculaire ont été mis en œuvre pour identifier les sources de contamination possibles.
Neuf sur 100 CP analysés (9 %) ont montré la contamination bactérienne ; l’analyse des ordres nucléotides a révélé la présence de microbiote caractéristique de la peau du donneur et du sol. Une relation clonale diverse entre les souches a été identifiée dans Staphylococcus epidermidis.
La détection de polluants associés à l’environnement et à la flore cutanée montre le besoin de mettre en œuvre des mesures dans le procédé de désinfection de la peau au site de phlébotomie et de nettoyer chacune des zones impliquées dans la collecte de sang.
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