Microbial community composition and its role in volatile compound formation during the spontaneous fermentation of ice wine made from Vidal grapes

Vidal grape grown in Ili, Xinjiang Autonomous Region, is one of few grapes used to ferment ice wine in China. Microbial community structure and volatile composition during the spontaneous fermentation of ice wine made from Vidal grapes in Ili were investigated using amplicon sequencing technology and headspace solid-phase microextraction/gas chromatography-mass spectrometer technologies. Among bacterial genera, Sphingobium, Pseudomonas and Sphingomonas gradually decreased, while Lactobacillus and Streptococcus increased during the spontaneous fermentation process. As regards fungi, the relative abundance of Vishniacozymaand Cladosporium reduced, but Hanseniaspora sharply raised. Additionally, correlations between microbes and volatile compounds were constructed based on multivariate data analysis. The results revealed that the functional core microbiota (mainly composed of eight bacterial genera and nine fungal genera) during ice wine fermentation showed considerable correlations with the formation of twenty-four volatile compounds in ice wine made from Vidal grapes. For example, Saccharomyces was positively correlated with ethanol, ethyl acetate and isoamylol; Hanseniaspora and Candidawere negatively correlated with hexanol; and Lactobacillus and Streptococcus were positively correlated with 2,3-butanediol, ethanol, ethyl acetate, isoamylol and isoamyl acetate. This studyprovides a reference for understanding the process of ice wine fermentation and improving the quality of ice wine made from Vidal grapes.     

Monitoring Seasonal Changes in Winery-Resident Microbiota

During the transformation of grapes to wine, wine fermentations are exposed to a large area of specialized equipment surfaces within wineries, which may serve as important reservoirs for two-way transfer of microbes between fermentations. However, the role of winery environments in shaping the microbiota of wine fermentations and vectoring wine spoilage organisms is poorly understood at the systems level. Microbial communities inhabiting all major equipment and surfaces in a pilot-scale winery were surveyed over the course of a single harvest to track the appearance of equipment microbiota before, during, and after grape harvest. Results demonstrate that under normal cleaning conditions winery surfaces harbor seasonally fluctuating populations of bacteria and fungi. Surface microbial communities were dependent on the production context at each site, shaped by technological practices, processing stage, and season. During harvest, grape- and fermentation-associated organisms populated most winery surfaces, acting as potential reservoirs for microbial transfer between fermentations. These surfaces harbored large populations of Saccharomyces cerevisiae and other yeasts prior to harvest, potentially serving as an important vector of these yeasts in wine fermentations. However, the majority of the surface communities before and after harvest comprised organisms with no known link to wine fermentations and a near-absence of spoilage-related organisms, suggesting that winery surfaces do not overtly vector wine spoilage microbes under normal operating conditions.     

Influence of Berry Heterogeneity on Phenolics and Antioxidant Activity of Grapes and Wines: A Primary Study of the New Winegrape Cultivar Meili (Vitis vinifera L.)

Wine grapes are usually harvested in vineyards when they ripen. However, not all of the berries in a vineyard ripen homogeneously because of different microclimates around the clusters and berries. In this study, the influence of berry heterogeneity on the phenolic content and antioxidant capacity of grapes and wines under a continental monsoon climate was evaluated for a new wine grape cultivar Meili (Vitis vinifera L.). The total phenolic, flavonoid, flavanol, and monomeric anthocyanin contents in the skin and wine significantly increased with grape density; however, there was no significant difference in the seeds between the two lower densities. The highest values of DPPH free radical-scavenging activity, cupric-reducing antioxidant capacity, and hydroxyl radical-scavenging activity in the skin, seed and wine were detected for the densest berries. The sum of individual phenolic compounds in skin, seed and wine increased with berry density, though no significant difference for skin was observed between the two higher density classes. Hence, the chemical components of Meili grapes and wines were positively associated with the berry density at harvest under the continental monsoon climate.     

Survey of mycobiota,black <Emphasis Type="Italic">Aspergillus</Emphasis> and ochratoxin A occurrence on Brazilian wine grapes

The southern state of Brazil is responsible for 90 % of the wine produced in the country; however, the mycobiota and the occurrence of ochratoxin A (OTA) on wine grapes produced in this region has never been fully characterized. To evaluate the fungal and OTA contamination in wine grapes of two varieties cultivated in southern Brazil, a survey was conducted in three regions with slightly different climates. From each region, samples were obtained at early ripeness and at harvest stage. Eight genera were isolated; Alternaria and Trichoderma were the most prevalent. Within the Aspergillus genus, the section Nigri was predominant. One uniseriate black Aspergillus was able to produce OTA under the conditions tested but no detectable levels of OTA were found in the grape samples. The low overall incidence of black Aspergillus and the absence of OTA on the grapes may be explained by the meteorological conditions at the analyzed regions, and characterizes a high quality of this product regarding mycotoxigenic contamination. This is the first study to fully describe the mycological biota of two wine grape varieties produced at three different regions of Rio Grande do Sul state.     

Evolution of Acetic Acid Bacteria During Fermentation and Storage of Wine

Acetic acid bacteria were present at all stages of wine making, from the mature grape through vinification to conservation. A succession of Gluconobacter oxydans, Acetobacter pasteurianus, and Acetobacter aceti during the course of these stages was noted. Low levels of A. aceti remained in the wine; they exhibited rapid proliferation on short exposure of the wine to air and caused significant increases in the concentration of acetic acid. Higher temperature of wine storage and higher wine pH favored the development and metabolism of these species.     

Berries contamination by microfungi in Slovakia vineyard regions: Impact of climate conditions on microfungi biodiversity

BackgroundWeather conditions can selectively promote the growth of particular fungal species, which cause rotting and spoilage of grape berries before harvest. The presence of pathogenic fungi can lead to the development of opportunist microfungi that can produce mycotoxins and cause grapes and wine contamination.ObjectiveThe variation of climatic conditions allowed to design a pilot study and address relevant questions for risk assessment of climate related mycotoxins production in grapes and in wine.MethodsMicrofungi contaminating berries during the vegetative period of year 2008 and 2009 in vineyards regions of Slovakia at the early veraison and at the ripening in harvest time have been identified.ResultsSpoilage fungi were more abundant in veraison for both years in all the studied geographical regions, with an average temperature of 20 °C, humidity between 60 and 80%, and precipitation in the range 6–5 mm. Much more strains of toxigenic fungi were found during veraison and ripening in the case of a year temperature variation in the range 17–22.5 °C, humidity values ranging from 58 to 80% and precipitations in the range 0.7–8.4 mm.ConclusionsThe results suggest that there is an effect of the climatic conditions on microfungi biodiversity.     

Inventory and monitoring of wine microbial consortia

The evolution of the wine microbial ecosystem is generally restricted to Saccharomyces cerevisiae and Oenococcus oeni, which are the two main agents in the transformation of grape must into wine by acting during alcoholic and malolactic fermentation, respectively. But others species like the yeast Brettanomyces bruxellensis and certain ropy strains of Pediococcus parvulus can spoil the wine. The aim of this study was to address the composition of the system more precisely, identifying other components. The advantages of the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) approach to wine microbial ecology studies are illustrated by bacteria and yeast species identification and their monitoring at each stage of wine production. After direct DNA extraction, PCR-DGGE was used to make the most exhaustive possible inventory of bacteria and yeast species found in a wine environment. Phylogenetic neighbor-joining trees were built to illustrate microbial diversity. PCR-DGGE was also combined with population enumeration in selective media to monitor microbial changes at all stages of production. Moreover, enrichment media helped to detect the appearance of spoilage species. The genetic diversity of the wine microbial community and its dynamics during winemaking were also described. Most importantly, our study provides a better understanding of the complexity and diversity of the wine microbial consortium at all stages of the winemaking process: on grape berries, in must during fermentation, and in wine during aging. On grapes, 52 different yeast species and 40 bacteria could be identified. The diversity was dramatically reduced during winemaking then during aging. Yeast and lactic acid bacteria were also isolated from very old vintages. B. bruxellensis and O. oeni were the most frequent.     

Survival of inoculated Saccharomyces cerevisiae strain on wine grapes during two vintages

AIMS: To investigate the influence of a specific ecological niche, the wine grape, on the survival and development of Saccharomyces cerevisiae. METHODS AND RESULTS: A strain with a rare phenotype was sprayed onto the grape surfaces and monitored through two vintages using a specific indicative medium and analysing the internal transcribed spacer regions in the 5.8S rDNA. During the ripening process, there was a progressive colonization of the surface of the undamaged and damaged grapes by epiphytic yeasts, up to the time of harvest. The damaged wine grapes showed a much greater epiphytic yeast population. However, the inoculated S. cerevisiae strain showed a scarce persistence on both undamaged and damaged wine grapes, and the damaged grapes did not appear to improve the grape surface colonization of this strain. CONCLUSIONS: Results indicated that wine grape is not a favourable ecological niche for the development and colonization of S. cerevisiae species. SIGNIFICANCE AND IMPACT OF THE STUDY: Results of this work are further evidence that S. cerevisiae is not specifically associated with natural environments such as damaged and undamaged wine grapes.     

Anthocyanin Profiles in Grape Berry Skins of Different Species of Wine Grapes in Shanxi,China

To understand the anthocyanin characteristics of wine grape varieties, the anthocyanin composition and content of 31 wine grape varieties were analyzed to explore the use of anthocyanins as chemical fingerprints to distinguish varieties. Results showed that a total of 21 anthocyanins were detected in the skins, including cyanidin, delphinidin, petunidin, peonidin and malvidin 3-monoglucosides (or 3,5-diglucosides) along with the corresponding acetyl and p-coumaroyl derivatives. The highest and lowest total amount of anthocyanins were detected in ‘Ruby Cabernet’ and ‘Muscat Rouge’, respectively. In the 21 Vitis vinifera grapes, there were 3~11 monoglucoside anthocyanins detected, however, there were 4 to 9 monoglucoside anthocyanins and 1~7 diglucoside anthocyanins detected in the 10 other species of grapes. Except for ‘Zhesexiang’ ‘Seibel Noir’, ‘44-6-7-1’ and ‘Beibinghong’, the contents of diglucoside anthocyanins in the other six varieties accounted for more than 52% of the total anthocyanins. Except for ‘Zhesexiang’, ‘Muscat Rouge’ and ‘Beibinghong’, the content of methylated anthocyanins accounted for more than 75% of total anthocyanins. There were significant differences in the anthocyanin types and contents in the skins among V. vinifera and other grapes. The results of the principal component analysis and the cluster classification of 31 grape varieties (lines) were nearly consistent, which suggested that anthocyanins can be used as chemical fingerprints to distinguish wine grape varieties.     

Mycotoxin production from fungi isolated from grapes

AIMS: In order to assess the potential for producing mycotoxins, fungi were isolated from wine producing grapes. METHODS AND RESULTS: The isolates were identified and Penicillium expansum, the most well recognized mycotoxin producer, was analysed for mycotoxin production by TLC. Many of the strains produced patulin and/or citrinin, often depending on whether they were grown on a grape or yeast extract sucrose media. CONCLUSION: Citrinin was produced by all strains grown in the yeast extract sucrose medium, but only one strain (from 51) was able to produce this compound in grape juice medium. Patulin was produced in the yeast extract medium by 20 strains and in grape juice medium by 33 strains. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of mycotoxins in wine producing grapes is discussed. Grapes contamination with patulin seems not to contribute to wine contamination, and no ochratoxin producing fungi was identified.     

Growth and ochratoxin A production by Aspergillus carbonarius at different pHs and grape maturation stages

Aims: The objective of this work was to study the effect of some factors, linked to grape composition during ripeness process, on the growth and ochratoxin A (OTA) production of Aspergillus carbonarius isolated from grapes. Methods and Results: Aspergillus carbonarius isolates were tested (i) in vitro, in Czapek yeast autolysate agar (CYA) at different pHs (2·5–4·5) and incubation times (2–6 days), and (ii) in situ, in fresh grapes collected at different maturation stages. Aspergillus carbonarius was able to grow with the same intensity at the different maturation stages and pH levels tested. In general, a similar trend of OTA production by A. carbonarius in response to acidity in media and in grape was observed. Low pH level seemed optimal for maximum OTA production. Conclusions: Aspergillus carbonarius strains can strongly grow and produce OTA on grape from the early stages of maturation. Extrinsic environmental conditions at the harvest period and skin thickness are, probably, the mains factors contributing to OTA contamination of grapes at the end of maturation. Significance and Impact of the Study: The results lead to a better understanding of the critical point during grape maturation for the growth of ochratoxigenic fungi and the toxin production.     

Table grape consumption reduces adiposity and markers of hepatic lipogenesis and alters gut microbiota in butter fat-fed mice

Our objective was to determine if consuming table grapes reduces adiposity and its metabolic consequences and alters gut microbiota in mice fed a high-fat (HF), butter-rich diet. C57BL/6 J mice were fed a low-fat (LF) diet or HF diet with 3% or 5% grapes for 11 weeks. Total body and inguinal fat were moderately but significantly reduced in mice fed both levels of grapes compared to their controls. Mice fed 5% grapes had lower liver weights and triglyceride levels and decreased expression of glycerol-3-phosphate acyltransferase (Gpat1) compared to the 5% controls. Mice fed 3% grapes had lower hepatic mRNA levels of peroxisome proliferator-activated receptor gamma 2, sterol-CoA desaturase 1, fatty-acid binding protein 4 and Gpat1 compared to the 3% controls. Although grape feeding had only a minor impact on markers of inflammation or lipogenesis in adipose tissue or intestine, 3% of grapes decreased the intestinal abundance of sulfidogenic Desulfobacter spp. and the Bilophila wadsworthia-specific dissimilatory sulfite reductase gene and tended to increase the abundance of the beneficial bacterium Akkermansia muciniphila compared to controls. In addition, Bifidobacterium, Lactobacillus, Allobaculum and several other genera correlated negatively with adiposity. Allobaculum in particular was increased in the LF and 3% grapes groups compared to the HF-fed controls. Notably, grape feeding attenuated the HF-induced impairment in epithelial localization of the intestinal tight junction protein zonula occludens. Collectively, these data indicate that some of the adverse health consequences of consuming an HF diet rich in saturated fat can be attenuated by table grape consumption.     

Exploring the biodiversity of two groups of Oenococcus oeni isolated from grape musts and wines: Are they equally diverse?

One hundred and four Oenococcus oeni isolates were characterised by the carbohydrate fermentation (CH) profile and DNA fingerprinting. Forty-four isolates came from grape must, and 60 from wines sampled at the end of alcoholic fermentation or during malolactic fermentation. The grape must isolates fermented more CH than the wine isolates. In genotypical terms, no clear boundary between grape must and wine isolates was found. Diversities were deduced by considering the isolates of grape must and of wine separately and jointly. By considering only CH fermentation abilities, the group of grape must isolates gave higher diversity index (DI_CH) values than those isolated from wine; i.e., these isolates were metabolically more diverse. The contrary occurred when the DNA fingerprints were used to calculate DI_RAPD-VNTR: wine isolates were genotypically more diverse than grape must ones. With a polyphasic approach, which considered metabolic and genotypic data, the diversity index of both isolate groups (from grape must and wine) was the same, 0.993, which was slightly lower than that calculated from all the isolates (0.997).     

Identification of indigenous yeast flora isolated from the five winegrape varieties harvested in Xiangning,China

Inoculated fermentation by selected indigenous yeast strains from a specific location could provide the wine with unique regional sensory characteristics. The identification and differentiation of local yeasts are the first step to understand the function of yeasts and develop a better strain-selection program for winemaking. The indigenous yeasts in five grape varieties, Chardonnay, Cabernet Franc, Cabernet Sauvignon, Marselan, and Merlot cultivated in Xiangning, Shanxi, China were investigated. Eight species of seven genera including Aureobasidium pullulans, Candida zemplinina, Hanseniaspora uvarum, Hanseniaspora occidentalis, Issatchenkia terricola, Metschnikowia pulcherrima, Pichia kluyveri, and Saccharomyces cerevisiae were identified using Wallerstein Laboratory Nutrient medium with sequencing of the 26S rDNA D1/D2 domain. H. uvarum and S. cerevisiae were the predominant species, while most non-Saccharomyces species were present in the whole fermentation process at different levels among the grape varieties. The genotypes of S. cerevisiae from each microvinification were determined by using interdelta sequence analysis. The 102 isolates showed eight different genotypes, and genotype III was the predominant genotype found. The distribution of S. cerevisiae strains during the fermentation of Marselan was also studied. Six genotypes were observed among the 92 strains with different genotypes of competitiveness at different sampling stages. Genotype V demonstrated the potential for organizing starter strains and avoiding inefficient fermentation. In general, this study explored the yeast species in the grapes grown in Xiangning County and provided important information of relationship of local yeast diversity and its regional wine sensory characteristics.     

Tracking cell wall changes in wine and table grapes undergoing Botrytis cinerea infection using glycan microarrays

Background and AimsThe necrotrophic fungus Botrytis cinerea infects a broad range of fruit crops including domesticated grapevine Vitis vinifera cultivars. Damage caused by this pathogen is severely detrimental to the table and wine grape industries and results in substantial crop losses worldwide. The apoplast and cell wall interface is an important setting where many plant–pathogen interactions take place and where some defence-related messenger molecules are generated. Limited studies have investigated changes in grape cell wall composition upon infection with B. cinerea, with much being inferred from studies on other fruit crops.MethodsIn this study, comprehensive microarray polymer profiling in combination with monosaccharide compositional analysis was applied for the first time to investigate cell wall compositional changes in the berries of wine (Sauvignon Blanc and Cabernet Sauvignon) and table (Dauphine and Barlinka) grape cultivars during Botrytis infection and tissue maceration. This was used in conjunction with scanning electron microscopy (SEM) and X-ray computed tomography (CT) to characterize infection progression.Key ResultsGrapes infected at veraison did not develop visible infection symptoms, whereas grapes inoculated at the post-veraison and ripe stages showed evidence of significant tissue degradation. The latter was characterized by a reduction in signals for pectin epitopes in the berry cell walls, implying the degradation of pectin polymers. The table grape cultivars showed more severe infection symptoms, and corresponding pectin depolymerization, compared with wine grape cultivars. In both grape types, hemicellulose layers were largely unaffected, as was the arabinogalactan protein content, whereas in moderate to severely infected table grape cultivars, evidence of extensin epitope deposition was present.ConclusionsSpecific changes in the grape cell wall compositional profiles appear to correlate with fungal disease susceptibility. Cell wall factors important in influencing resistance may include pectin methylesterification profiles, as well as extensin reorganization.