Search

The aromatic profile of wine determines its overall final quality, and among the volatile molecules that define it, varietal thiols are responsible for shaping the distinctive character of certain wine varieties. In grape must, these thiols are conjugated to amino acids or small peptides in a non-volatile form. During wine fermentation, yeasts play a principal role in expressing these aromatic compounds as they internalise and cleavage these precursors, releasing the corresponding free and aroma-impacting fraction. Here, we investigate the impact of three wine yeasts (Saccharomyces cerevisiae, Torulaspora delbrueckii and Lachancea thermotolerans) on thiol releasing in synthetic grape must fermentations supplemented with different cysteinylated (Cys-4MSP and Cys-3SH) and glutathionylated (GSH-4MSP and GSH-3SH) precursors. We demonstrate higher consumption levels of cysteinylated precursors, and consequently, higher amounts of thiols are released from them compared to glutathionylated ones. We also report a significant impact of yeast inoculated on the final thiols released. Meanwhile T. delkbrueckii exhibits a great 3SHA releasing capacity, L. thermotolerans stands out because of its high 3SH release. We also highlight the synergic effect of the co-inoculation strategy, especially relevant in the case of S. cerevisiae and L. thermotolerans mixed fermentation, that has an outstanding release of 4MSP thiol. Although our results stem from a specific experimental approach that differs from real winemaking situations, these findings reveal the potential of unravelling the specific role of different yeast species, thiol precursors and their interaction, to improve wine production processes in the context of wine aroma enhancement., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Hanseniaspora vineae exhibits extraordinary positive oenological characteristics contributing to the aroma and texture of wines, especially by its ability to produce great concentrations of benzenoid and phenylpropanoid compounds compared with conventional Saccharomyces yeasts. Consequently, in practice, sequential inoculation of H. vineae and Saccharomyces cerevisiae allows to improve the aromatic quality of wines. In this work, we evaluated the impact on wine aroma produced by increasing the concentration of phenylalanine, the main amino acid precursor of phenylpropanoids and benzenoids. Fermentations were carried out using a Chardonnay grape juice containing 150 mg N/L yeast assimilable nitrogen. Fermentations were performed adding 60 mg/L of phenylalanine without any supplementary addition to the juice. Musts were inoculated sequentially using three different H. vineae strains isolated from Uruguayan vineyards and, after 96 h, S. cerevisiae was inoculated to complete the process. At the end of the fermentation, wine aromas were analysed by both gas chromatography-mass spectrometry and sensory evaluation through a panel of experts. Aromas derived from aromatic amino acids were differentially produced depending on the treatments. Sensory analysis revealed more floral character and greater aromatic complexity when compared with control fermentations without phenylalanine added. Moreover, fermentations performed in synthetic must with pure H. vineae revealed that even tyrosine can be used in absence of phenylalanine, and phenylalanine is not used by this yeast for the synthesis of tyrosine derivatives., Competing Interests: Declaration of competing interest All authors of the manuscript declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The brewing ability of wild yeast strains obtained from forest and vineyards ecosystems was analysed and compared with commercial yeast strains. The selection of new yeast strains as a way to create new beer aromas and flavours and to use local strains to promote the proximity ingredients in brewing is a topic of interest in the craft beer sector. Seventy-six wild Saccharomyces and non-Saccharomyces isolates and eighteen control strains were evaluated for their enzymatic activity and brewing capacity. The early screening system was set up to profile their enzymatic activity, utilisation of wort sugars and the effect of hop acids and ethanol on yeast growth. The microvolume screening method allows a large number of samples to be studied at the same time, permitting an affordable and rapid characterization in a relatively short period of time. Twenty-eight strains were selected using this method and tested in small-scale fermentations. Finally, three of these strains, all belonging to the species Lachancea thermotolerans, showed great potential and adaptability to ferment different wort styles, although further studies will be necessary to test their possibilities as beer starters. Understanding yeast enzymatic profiles and the influence of beer ingredients on their fermentation activity provides a platform to select strains for further consideration in brewing research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Chitosan is an active highly charged polysaccharide that has initially been developed in oenology to eliminate the spoilage yeast B. bruxellensis. However, different forms of chitosan exist, some complying with EU regulation for their use in wines, others not. Moreover, with the trend in oenology of limiting SO 2 , more and more questions arise as to the impact of chitosan on other microorganisms of the grape and wine environment. We investigated the antimicrobial efficiency of chitosan on a large oenological microbial collection, englobing technological as well as spoilage microorganisms. Results show that most species are affected at least transiently. Furthermore, a high variability prevails within most species and sensitive, intermediate and tolerant strains can be observed. This study also highlights different efficiencies depending on the wine parameters or the winemaking stage, giving important indications on which winemaking issues can be solved using chitosan. Chitosan treatment does not seem to be appropriate to limit the musts microbial pressure and Saccharomyces cerevisiae cannot be stopped during alcoholic fermentation, especially in sweet wines. Likewise, acetic acid bacteria are poorly impacted by chitosan. After alcoholic fermentation, chitosan can efficiently limit non-Saccharomyces yeast and lactic acid bacteria but special care should be given as to whether malolactic fermentation is wanted or not. Indeed, O. oeni can be severely impacted by chitosan, even months after treatment. Finally, this study highlights the crucial importance of the chitosan type used in its efficiency towards microbial stabilization. While a high molecular weight chitosan has limited antimicrobial properties, a chitosan with a much lower one, complying with EU and OIV regulation and specifications for its use in wine is much more efficient., Competing Interests: Declaration of competing interest The authors declare that they have no competing interest., (Copyright © 2022. Published by Elsevier B.V.)

A complex consortium of yeasts is the principal responsible of wine fermentation, being Saccharomyces cerevisiae the main driver. The use of selected yeast, beginning with Saccharomyces strains, is one of the main achievements in microbiological control in the wine industry. However, the use of single strain starters of S. cerevisiae and the limited variability of strains has increased the objections to its use due to the production of wines with a homogeneous profile. New tendencies in winemaking have emphasized the microbiological terroir and challenged the use of selected starters from different areas, including Non-Saccharomyces yeast or multi-strain starters in order to add complexity to the biochemical composition of wines. Nevertheless, these strategies also harbor their own challenges. In the present mini-review, we focus on the alternatives to current commercial yeast starters mainly based on the local multispecies starters or controlled spontaneous fermentations, considering the advantages and limitations of each strategy. Also, we present an ancestral technique based on the use of pre-fermented must (Pied-de-Cuve) because it provides certain microbial control to the alcoholic fermentation while allows the development of autochthonous microorganisms that might confer microbial typicity to the produced wines. Nevertheless, the latest strategy needs further research to establish a scientific background for the selection of the best Pied-de-Cuve development. Finally, the tendencies in winemaking should find a commitment between microbial control to guarantee alcoholic fermentation fulfillment and the production of wines reflecting microbial typicity to respond to consumer demands, without forgetting the scaling up in the cellars., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Oenococcus oeni is the main agent responsible for malolactic fermentation (MLF) in wine. This usually takes place in red wines after alcoholic fermentation (AF) carried out by Saccharomyces cerevisiae. In recent years, there is an increasing interest in using non-Saccharomyces yeast, usually in combination with S. cerevisiae, to improve wine quality. Current studies report a stimulatory effect of non-Saccharomyces on MLF, generally related to a decrease in the inhibitor compounds found in wine. In this work, we followed a comparative multi-omics approach, including transcriptomic and proteomic analysis, to study the molecular adaptation of O. oeni in wines fermented with Torulaspora delbrueckii and Metschnikowia pulcherrima, two of the most frequently used non-Saccharomyces, in sequential inoculation with S. cerevisiae. We compared the results to the adaptation of O. oeni in S. cerevisiae wine to determine the main changes arising from the use of non-Saccharomyces. The duration of MLF was shortened when using non-Saccharomyces, to half the time with T. delbrueckii and to a quarter with M. pulcherrima. In this work, we observed for the first time how O. oeni responds at molecular level to the changes brought about by non-Saccharomyces. We showed a differential adaptation of O. oeni in the wines studied. In this regard, the main molecular functions affected were amino acid and carbohydrate transport and metabolism, from which peptide metabolism appeared as a key feature under wine-like conditions. We also showed that the abundance of Hsp20, a well-known stress protein, depended on the duration time. Thus, the use of non-Saccharomyces reduced the abundance of Hsp20, which could mean a less stressful wine-like condition for O. oeni., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The isolation of autochthonous yeast species presents a good strategy to select new microorganisms for developing an adequate inoculum to carry out fermentations and generate representative products of the cider production zone. However, non-Saccharomyces yeasts have been considered to have low capacity to carry out a complete fermentation as Saccharomyces cerevisiae. In this work, five autochthonous yeasts from a cider fermentation process were isolated and identified as Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia membranaefaciens, P. kluyveri and Zygosaccharomyces rouxii. A series of fermentations were developed at laboratory level, using each species individually and it was observed that only S. cerevisiae was able to finish the process. K. marxianus consumed less than 50% of the sugars; P. kluyveri and Z. rouxii consumed less than 70% and P. membranaefaciens consumed more than 90% but the yield (ethanol produced for sugar consumed (Y P/S )) was 0.39. Nevertheless, the addition of magnesium, zinc and nitrogen increased the fermentative capacity of almost all species: K. marxianus, Z. rouxii and P. kluyveri, showed an increase in ethanol production when nutrients were added, obtaining more than 80 g/L of ethanol, and showing that those nutrients are necessary to complete the fermentation. This work describes the potential use of different non-Saccharomyces species to carry out fermentation of apple juice and highlights the importance of certain nutrients to enable an efficient alcoholic fermentation and the generation of desirable volatile compounds for cider production., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Non-Saccharomyces yeasts have increasingly been used in vinification recently. This is particularly true of Torulaspora delbrueckii and Metschnikowia pulcherrima, which are inoculated before S. cerevisiae, to complete a sequential alcoholic fermentation. This paper aims to study the effects of these two non-Saccharomyces yeasts on malolactic fermentation (MLF) carried out by two strains of Oenococcus oeni, under cellar conditions. Oenological parameters, and volatile and phenolic compounds were analysed in wines. The wines were tasted, and the microorganisms identified. In general, non-Saccharomyces created more MLF friendly conditions, largely because of lower concentrations of SO 2 and medium chain fatty acids. The most favourable results were observed in wines inoculated with T. delbrueckii, that seemed to promote the development of O. oeni and improve MLF performance., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The use of non-Saccharomyces yeast in conjunction with Saccharomyces cerevisiae in wine fermentation is a growing trend in the wine industry. Non-Saccharomyces, through their distinctive production of secondary metabolites, have the potential to positively contribute to wine sensory profile. To discover new candidate strains for development as starter cultures, indigenous non-Saccharomyces were isolated from un-inoculated fermenting Shiraz musts from a South Australian vineyard (McLaren Vale wine region) and characterised. Among the 77 isolates, 7 species belonging to 5 genera (Kazachstania, Aureobasidium, Meyerozyma, Wickerhamomyces and Torulaspora) were identified by sequencing the internal transcribed spacer regions of the 5.8S rRNA gene (ITS1-5.8S-ITS2 region). The indigenous isolates were evaluated for oenological properties, namely, ethanol tolerance, enzyme activity, and H 2 S production. To determine their potential industrial use as starter cultures, representative isolates of each species were assessed in a sterile chemically defined grape juice and Viognier grape juice to evaluate their contribution to fermentation kinetics and production of key metabolites, including volatile compounds., (Copyright © 2019 Elsevier B.V. All rights reserved.)

To obtain beverages with reduced alcohol content, the use of unripe grapes, with low sugar and high malic acid concentration, was recently explored. Due to the low sugar, ethanol and glycerol production is limited during fermentation affecting important sensory aspects such as the palate fullness of these beverages. The high acidity influences their organoleptic quality, as well. So far, only S. cerevisiae starter, used in conventional fermentations, have been tested in this condition, and no selection has been performed to identify alternative yeasts suitable for unripe grape fermentation. S. bacillaris is known for the low ethanol tolerance, high glycerol and moderate volatile acidity production. Therefore, this non- Saccharomyces yeast have been investigated to improve the quality of low-alcohol beverages. Seven S. bacillaris strains were tested in synthetic musts with different sugar and malic acid levels, mimicking natural ripe and unripe grape musts. In all the tested conditions, S. bacillaris produced higher glycerol than S. cerevisiae. In single-strain fermentation at low sugar and high malic acid no S. bacillaris strains was able to transform all the sugars, although the produced ethanol was lower than that at high sugar condition. Therefore, sequential fermentations with S. cerevisiae were evaluated at low sugar and high malic acid. In this condition all the sugars were consumed and a significant glycerol increase was found. These results were confirmed when sequential fermentations were run in natural unripe grape must. Moreover, an increase in malic acid degradation, with respect to EC1118 single-strain fermentation, was observed., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A total of 512 yeasts, including 422 non-Saccharomyces yeasts, were isolated from various fruits including apple, aronia, Muscat Bailey A grapes, and persimmon. These were used to prepare persimmon wine and apple cider starters that produced high levels of aromatic compounds, which contribute to high-quality fermented products. Environmental tolerance testing with 20% glucose and 8% EtOH, alongside a sniffing test, led to the selection of Wickerhamomyces anomalus (Synonym Pichia anomala) SJ20, Meyerozyma caribbica (Synonym Pichia caribbica) YP1, Pichia kluyveri CD34, Hanseniaspora uvarum SJ69 (for persimmon wine), W. anomalus CS7-16 (for apple cider), and Starmerella bacillaris (Synonym Candida zemplinina) CD80 (for both wines) as wine starters. These strains had high environmental stress tolerance and the highest sniffing test scores. Persimmon wine and apple cider were fermented using these strains in single- or mixed-culture with S. cerevisiae W-3 to determine the improved effect on wine aroma. In accordance with the results of volatile ester compounds and sensory evaluation, W. anomalus SJ20, H. uvarum SJ69, and W. anomalus CS7-16 had an excellent potential as persimmon wine and apple cider starters. Moreover, other strains also showed a good potential for a distinctive persimmon wine and apple cider because of the different compositions of the various volatile ester compounds. Six types of sugars (fructose, glucose, maltose, sucrose, raffinose, sucrose, and trehalose), four types of rehydration solutions (distilled water, 1× phosphate buffered saline, 0.85% NaCl, and 1% peptone water), and two types of antioxidants (l-ascorbic acid and glutathione) were examined to improve the survival rate of air-blast dried non-Saccharomyces yeast cells. Optimal sugar and rehydration conditions for each strain were validated, and scanning electron microscopy showed that each cell was surrounded by protectants, including sugar, skim milk, and lactomil. Storability assessment of air-blast dried yeast cells maintained at 4 °C for two months indicated that at least one condition in each strain had a higher survival rate than the control, regardless of the concentration or type of antioxidant treatment, except for M. caribbica YP1. These results suggest that antioxidant treatment contributes to maintaining the viability of air-blast dried cells in hostile environments., (Copyright © 2018. Published by Elsevier B.V.)

The aim of this study was to characterize the yeast consortium isolated from Grignolino grapes in a newly planted vineyard in Piedmont (Italy) via analysis of the intra-vineyard yeast distribution of grape samples from single rows. A two-phase approach allowed the identification of culturable yeasts present on grape skins and, through an enriching procedure via grape fermentation, the isolation of low frequency non-Saccharomyces and Saccharomyces spp. fermentative species, including S. paradoxus, which is highly unusual during grape fermentation, along with the intra-specific characterization of S. cerevisiae isolates. Culture-based molecular techniques revealed a grape yeast microbiota formed by (in order of abundance) Hanseniaspora uvarum, the yeast-like fungus Aerobasidium pullulans, Candida zemplinina, Pichia kluyveri, Candida californica, Curvibasidium cygneicollum, Meyerozima caribbica, Rhodotorula babjevae, Metschnikowia pulcherrima and Cryptococcus flavescens. Technological properties of isolated Saccharomyces spp. strains were analysed, identifying strains, including S. paradoxus, potentially suitable as an ecotypical starter for territorial wines., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The use of mixed culture fermentations with selected Starmerella bacillaris and Saccharomyces cerevisiae strains is gaining winemaking attention, mainly due to their ability to enhance particular characteristics in the resulting wines. In this context, yeast interspecies interactions during fermentation have a fundamental role to determine the desired product characteristics, since they may modulate yeast growth and as a consequence metabolite production. In order to get an insight into these interactions, the growth and death kinetics of the abovementioned species were investigated in pure and mixed culture fermentations, using cv. Nebbiolo grape must. Trials were conducted in flasks but also in a double-compartment fermentation system in which cells of the two species were kept separate by a filter membrane. Although the two species had similar growth pattern during the first days of fermentation, Starm. bacillaris died earlier when tested in the flask than in the double-compartment fermentor. The early death of Starm. bacillaris seemed to be not caused by nutrient limitation nor by accumulation of growth inhibitory compounds (which were not measured in the present study). Rather, cell-to-cell contact mechanism, dependent on the presence of viable S. cerevisiae cells, appears to be responsible for the observations made. These results contribute to better understand the factors that influence Starm. bacillaris death during wine fermentations., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In last years, non-Saccharomyces yeasts have emerged as innovative tools to improve wine quality, being able to modify the concentration of sensory-impact compounds. Among them, varietal thiols released by yeasts, play a key role in the distinctive aroma of certain white wines. In this context, Torulaspora delbrueckii is in the spotlight because of its positive contribution to several wine quality parameters. This work studies the physiological properties of an industrial T. delbrueckii strain, for the production of wines with increased thiol concentrations. IRC7 gene, previously described in S. cerevisiae, has been identified in T. delbrueckii, establishing the genetics basis of its thiol-releasing capability. Fermentations involving T. delbrueckii showed improvements on several parameters (such as glycerol content, ethanol index, and major volatile compounds composition), but especially on thiols release. These results confirm the potential of T. delbrueckii on wine improvement, describing new metabolic features regarding the release of cysteinylated aroma precursors., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Saccharomyces cerevisiae is the most important yeast species for the production of wine and other beverages. In addition, nowadays, researchers and winemakers are aware of the influence of non-Saccharomyces in wine aroma complexity. Due to the high microbial diversity associated to several agro-food processes, such as winemaking, developing fast and accurate methods for microbial identification is demanded. In this context, MALDI-TOF MS mass fingerprint provides reliable tool for fast biotyping and classification of microorganisms. However, there is no versatile and standardized method for fungi currently available. In this study, an optimized sample preparation protocol was devised for the biotyping of yeasts of oenological origin. Taking into account that commercially available reference databases comprise almost exclusively clinical microorganisms, most of them bacteria, in the present study a database of yeasts isolated from vineyards and wineries was created, and its accuracy was tested using industrial and laboratory yeast strains. In addition, the implementation of a program for MALDI-TOF MS spectra analysis has been developed as an extensible open-source platform for MALDI data processing and analysis with statistical techniques that has arisen from our previous experience working with MALDI data. The software integrates two R packages for raw MALDI data preprocessing: Continuous Wavelet Transform (CWT)-based algorithm and MassSpecWavelet. One of the advantages of the CWT is that it can be directly applied to a raw spectrum, without prior baseline correction. Mass fingerprints of 109 S. cerevisiae strains and 107 non-Saccharomyces isolates were generated by MALDI-TOF MS upon optimized sample preparation and instrument settings and analyzed for strain, species, and genus-level differentiation. As a reference method, for S. cerevisiae differentiation at strain level, the analysis of the polymorphism in the inter-delta region was chosen. The data revealed that MALDI-TOF MS can be used for the rapid and accurate identification of S. cerevisiae and non-Saccharomyces isolates at genus and species level. However, S. cerevisiae differentiation at strain level was not successfully achieved, and the differentiation among Metschnikowia species was also difficult., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Strategies for production of wines containing lower alcohol concentrations are in strong demand, for reasons of quality, health, and taxation. Development and application of wine yeasts that are less efficient at transforming grape sugars into ethanol has the potential to allow winemakers the freedom to make lower alcohol wines from grapes harvested at optimal ripeness, without the need for post-fermentation processes aimed at removing ethanol. We have recently shown that two non-conventional wine yeast species Metschnikowia pulcherrima and Saccharomyces uvarum were both able to produce wine with reduced alcohol concentration. Both species produced laboratory-scale wines with markedly different volatile aroma compound composition relative to Saccharomyces cerevisiae. This work describes the volatile composition and sensory profiles of reduced-alcohol pilot-scale Merlot wines produced with M. pulcherrima and S. uvarum. Wines fermented with M. pulcherrima contained 1.0% v/v less ethanol than S. cerevisiae fermented wines, while those fermented with S. uvarum showed a 1.7% v/v reduction in ethanol. Compared to S. cerevisiae ferments, wines produced with M. pulcherrima showed higher concentrations of ethyl acetate, total esters, total higher alcohols and total sulfur compounds, while wines fermented with S. uvarum were characterised by the highest total concentration of higher alcohols. Sensorially, M. pulcherrima wines received relatively high scores for sensory descriptors such as red fruit and fruit flavour and overall exhibited a sensory profile similar to that of wine made with S. cerevisiae, whereas the main sensory descriptors associated with wines fermented with S. uvarum were barnyard and meat. This work demonstrates the successful application of M. pulcherrima AWRI3050 for the production of pilot-scale red wines with reduced alcohol concentration and highlights the need for rigorous evaluation of non-conventional yeasts with regard to their sensory impacts., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The respiratory metabolism of yeast species alternative to Saccharomyces cerevisiae has been explored in recent years as a tool to reduce ethanol content in grape wine. The efficacy of this strategy has been previously proven for mixed cultures of non-Saccharomyces and S. cerevisiae strains. In this work, we perform a transcriptomic analysis of the Crabtree-negative yeast Kluyveromyces lactis under tightly controlled growth conditions in order to better understand physiology of non-Saccharomyces yeasts during the fermentation of grape must under aerated conditions. Transcriptional changes in K. lactis are mainly driven by oxygen limitation, iron requirement, and oxidative stress. Oxidative stress appears as a consequence of the hypoxic conditions achieved by K. lactis once oxygen supply is no longer sufficient to sustain fully respiratory metabolism. This species copes with low oxygen and iron availability by repressing iron consuming pathways and activating iron transport mechanisms. Most of the physiological and transcriptomic features of K. lactis in aerobic wine fermentation are not shared with the Crabtree-positive yeast S. cerevisiae., (Copyright © 2017. Published by Elsevier B.V.)

Advances in microbial wine biotechnology have led to the recent commercialization of several non-Saccharomyces starter cultures. These are intended to be used in either simultaneous or sequential inoculation with Saccharomyces cerevisiae. The different types of microbial interactions that can be stablished during wine fermentation acquire an increased relevance in the context of these mixed-starter fermentations. We analysed the transcriptional response to co-cultivation of S. cerevisiae and Torulaspora delbrueckii. The study focused in the initial stages of wine fermentation, before S. cerevisiae completely dominates the mixed cultures. Both species showed a clear response to the presence of each other, even though the portion of the genome showing altered transcription levels was relatively small. Changes in the transcription pattern suggested a stimulation of metabolic activity and growth, as a consequence of the presence of competitors in the same medium. The response of S. cerevisiae seems to take place earlier, as compared to T. delbrueckii. Enhanced glycolytic activity of the mixed culture was confirmed by the CO 2 production profile during these early stages of fermentation. Interestingly, HSP12 expression appeared induced by co-cultivation for both of S. cerevisiae and Torulaspora delbrueckii in the two time points studied. This might be related with a recently described role of Hsp12 in intercellular communication in yeast. Expression of S. cerevisiae PAU genes was also stimulated in mixed cultures., (Copyright © 2016. Published by Elsevier B.V.)

A pineapple vinification process was conducted through inoculated and spontaneous fermentation to develop a process suitable for a quality beverage during two successive vintages in Huambo, Angola. Wines obtained with the conventional Saccharomyces cerevisiae strain, were analysed by gas chromatography, and a total of 61 volatile constituents were detected in the volatile fraction and 18 as glycosidically bound aroma compounds. Concentration levels of carbonyl and sulphur compounds were in agreement with the limited information reported about pineapple fruits of other regions. We report, for the first time in pineapple wines, the presence of significant concentrations of lactones, ketones, terpenes, norisoprenoids and a variety of volatile phenols. Eight native yeast strains were isolated from spontaneous batches. Further single-strain fermentations allowed us to characterise their suitability for commercial fermentation. Three native strains (Hanseniaspora opuntiae, H. uvarum and Meyerozyma guilliermondii) were selected with sensory potential to ferment pineapple fruits with increased flavour diversity. Results obtained here contribute to a better understanding of quality fermentation alternatives of this tropical fruit in subtropical regions., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Over the last few years the use of multi-starter inocula has become an attractive biotechnological practice in the search for wine with high flavour complexity or distinctive characters. This has been possible through exploiting the particular oenological features of some non-Saccharomyces yeast strains, and the effects that derive from their specific interactions with Saccharomyces. In the present study, we evaluated the selected strain Zygotorulaspora florentina (formerly Zygosaccharomyces florentinus) in mixed culture fermentations with Saccharomyces cerevisiae, from the laboratory scale to the winery scale. The scale-up fermentation and substrate composition (i.e., white or red musts) influenced the analytical composition of the mixed fermentation. At the laboratory scale, mixed fermentation with Z. florentina exhibited an enhancement of polysaccharides and 2-phenylethanol content and a reduction of volatile acidity. At the winery scale, different fermentation characteristics of Z. florentina were observed. Using Sangiovese red grape juice, sequential fermentation trials showed a significantly higher concentration of glycerol and esters while the sensorial analysis of the resulting wines showed higher floral notes and lower perception of astringency. To our knowledge, this is the first time that this yeasts association has been evaluated at the winery scale indicating the potential use of this mixed culture in red grape varieties., (Copyright © 2016. Published by Elsevier B.V.)

Pectinase enzymes have shown a considerable influence in both, sensitive and technological properties of wines. They can help to improve clarification process, releasing more color and flavor compounds entrapped in grape skin, facilitating the liberation of phenolic compounds. This work aims to find yeasts that, because of their native pectinases, can be applied on combined fermentations with Saccharomyces cerevisiae obtaining significant benefits over single-inoculated traditional fermentations. 462 yeast strains isolated from wineries were identified and tested for several enzymatic activities of recognized interest for enology industry. Considering the 7 identified species, only Aureobasidium pullulans, Metschnikowia pulcherrima and Metschnikowia fructicola showed polygalacturonase activity. Because of its interest in winemaking, due to its reported incidence in wine flavor, the impact of M. pulcherrima as a source of pectinolytic enzymes was analyzed by measuring its influence in filterability, turbidity and the increase on color, anthocyanin and polyphenol content of wines fermented in combination with S. cerevisiae. Among the strains screened, M. pulcherrima NS-EM-34 was selected, due to its polygalacturonase activity, for further characterization in both, laboratory and semi-industrial scale assays. The kinetics concerning several metabolites of enological concern were followed during the entire fermentation process at microvinification scale. Improved results were obtained in the expected parameters when M. pulcherrima NS-EM-34 was used, in comparison to wines fermented with S. cerevisiae alone and combined with other pectinolytic and non-pectinolytic yeasts (A. pullulans and Lachancea thermotolerans, respectively), even working better than commercial enzymes preparations in most parameters. Additionally, M. pulcherrima NS-EM-34 was used at a semi-industrial scale combined with three different S. cerevisiae strains, confirming its potential application for red wine improvement on the mentioned sensorial and technological properties., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The aim of this work was to study ester formation and the aromatic impact of Torulaspora delbrueckii when used in association with Saccharomyces cerevisiae during the alcoholic fermentation of must. In order to evaluate the influence of the inoculation procedure, sequential and simultaneous mixed cultures were carried out and compared to pure cultures of T. delbrueckii and S. cerevisiae. Our results showed that mixed inoculations allowed the increase, in comparison to S. cerevisiae pure culture, of some esters specifically produced by T. delbrueckii and significantly correlated to the maximal T. delbrueckii population reached in mixed cultures. Thus, ethyl propanoate, ethyl isobutanoate and ethyl dihydrocinnamate were considered as activity markers of T. delbrueckii. On the other hand, isobutyl acetate and isoamyl acetate concentrations were systematically increased during mixed inoculations although not correlated with the development of either species but were rather due to positive interactions between these species. Favoring T. delbrueckii development when performing sequential inoculation enhanced the concentration of esters linked to T. delbrueckii activity. On the contrary, simultaneous inoculation restricted the growth of T. delbrueckii, limiting the production of its activity markers, but involved a very important production of numerous esters due to more important positive interactions between species. These results suggest that the ester concentrations enhancement via interactions during mixed modalities was due to S. cerevisiae production in response to the presence of T. delbrueckii. Finally, sensory analyses showed that mixed inoculations between T. delbrueckii and S. cerevisiae allowed to enhance the complexity and fruity notes of wine in comparison to S. cerevisiae pure culture. Furthermore, the higher levels of ethyl propanoate, ethyl isobutanoate, ethyl dihydrocinnamate and isobutyl acetate in mixed wines were found responsible for the increase of fruitiness and complexity., (Copyright © 2015 Elsevier B.V. All rights reserved.)

High alcohol concentrations reduce the complexity of wine sensory properties. In addition, health and economic drivers have the wine industry actively seeking technologies that facilitate the production of wines with lower alcohol content. One of the simplest approaches to achieve this aim would be the use of wine yeast strains which are less efficient at transforming grape sugars into ethanol, however commercially available wine yeasts produce very similar ethanol yields. Non-conventional yeast, in particular non-Saccharomyces species, have shown potential for producing wines with lower alcohol content. These yeasts are naturally present in the early stages of fermentation but in general are not capable of completing alcoholic fermentation. We have evaluated 48 non-Saccharomyces isolates to identify strains that, with limited aeration and in sequential inoculation regimes with S. cerevisiae, could be used for the production of wine with lower ethanol concentration. Two of these, Torulaspora delbrueckii AWRI1152 and Zygosaccharomyces bailii AWRI1578, enabled the production of wine with reduced ethanol concentration under limited aerobic conditions. Depending on the aeration regime T. delbrueckii AWRI1152 and Z. bailii AWRI1578 showed a reduction in ethanol concentration of 1.5% (v/v) and 2.0% (v/v) respectively, compared to the S. cerevisiae anaerobic control., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Non-Saccharomyces yeasts include different species which comprise an ecologically and biochemically diverse group capable of altering fermentation dynamics and wine composition and flavour. In this study, single- and mixed-culture of Hanseniaspora guilliermondii and Saccharomyces cerevisiae were used to ferment natural grape-juice, under two nitrogen regimes. In single-culture the strain H. guilliermondii failed to complete total sugar breakdown even though the nitrogen available has not been a limiting factor of its growth or fermentative activity. In mixed-culture, that strain negatively interfered with the growth and fermentative performance of S. cerevisiae, resulting in lower fermentation rate and longer fermentation length, irrespective of the initial nitrogen concentration. The impact of co-inoculation on the volatile compounds profile was more evident in the wines obtained from DAP-supplemented musts, characterised by increased levels of ethyl and acetate esters, associated with fruity and floral character of wines. Moreover, the levels of fatty acids and sulphur compounds which are responsible for unpleasant odours that depreciate wine sensory quality were significantly lower. Accordingly, data obtained suggests that the strain H. guilliermondii has potential to be used as adjunct of S. cerevisiae in wine industry, although possible interactions with S. cerevisiae still need to be elucidated., (Copyright © 2013 Elsevier B.V. All rights reserved.)