Month: July 2018

Healthy grapes for a good microbiome and wine

By Maria del Carmen Portillo

The grape berry surface hosts a microbiota of filamentous fungi, yeast, and bacteria that can have an impact on grape and wine quality (Fleet, 2003; Riberéau-Gayon et al., 2006). When the grape surface is altered (e.g. by damaged skin of the berry, highly compact bunches, excess of humidity, phytopathogen infections) the diversity and the population sizes of the microbiota are affected and can lead to the spoilage of the berry. Grape damage of the harvested bunches and the alteration of the grape ecological balance may compromise the vinification process and the final wine quality typically adding off-flavors (Steel et al., 2013). Thus, it is important to further investigate the microbiota diversity changes in damaged grapes and its influence on the alcoholic fermentation.

 

Figure 1. The changes in chemical composition and microbiome put at risk the fermentation of the must and the quality of the final produced wine.

 

Sour rot and Botrytis infections are the most common causes of heavy grape berry crop losses. The sour rot affects mostly dense bunches close to harvesting and is typically characterized by vinegar odour and brown berries. Disease aetiology is related with the skin rupture of the berry caused by physical factors (e.g. rain, hail, berry abrasion) or biological factors (e.g. insects, birds, moulds). The injuries on grape skin contribute to the development of yeasts and bacteria considered as the main responsible agents of this rot (Huber et al., 2011). Moreover, insects are an important source of microorganisms that can colonize grapes and proliferate once the injury in the skin is done (Barata et al., 2012). Botrytis infection (also known as grey mold) is frequent in vineyards exposed to cold and wet conditions during the ripening period (Nigro et al., 2006). In the case of sweet wines, where the presence of Botrytis cinerea is desired, the grapes are subjected to an extended ripening before harvesting and to a prolonged period of drying before crushing to enhance the abundance of B. cinerea (Stefanini et al., 2016).
Previous studies have documented the microbiota in sound and damaged grapes, including sour rotten and Botrytis-affected grapes (Barata et al., 2012; Mateo et al., 2014; Nisiotou et al., 2011). The results described how grape spoilage affects the grape microbiota, with damaged grapes harboring the highest yeast and acetic acid bacteria (AAB) population (Barata et al., 2008; Mateo et al., 2014). However, most of these studies use culture based techniques probably leading to underestimation of the microbial species involved. Currently, it is accepted that culture-isolated microorganisms are not necessarily representative of the microbial diversity (Amann et al., 1995; Rantsiou et al., 2005). Thus, the reported species selected during grape damaged by sour rot or Botrytis might be biased by the composition of culture media and the capacity of the microbes to grow on them (Cocolin et al., 2000; Millet and Lonvaud-Funel, 2000).

Figure 2. Sour rot and Botrytis infections are the most common causes of heavy grape berry crop losses.

 

Recently, several culture-independent methods based on the genetic background have been used to analyze the microbial diversity from grapes to wine (reviewed in Cocolin et al., 2011). Generally, the use of molecular biology methods has not only endorsed the traditional results but has also been able to identify higher microbial diversity than previously expected. Despite the potential of molecular techniques, we have just found one work where these were applied to study the microbial diversity of Botrytis-affected grapes (Nisiotou et al., 2011). Specifically, these authors used PCR-DGGE to monitor the yeast population changes during spontaneous fermentations of sound and Botrytis-affected grapes. The results included the detection of some bacterial genera not detected before in sour rot or botrytized musts like Enterobacter, Bacillus and Staphylococcus, some of them capable to survive in fermenting musts (Nisiotou et al., 2011).
Among molecular methods, massive sequencing (MS) technologies are becoming a widely used methodology to characterize more precisely the microbial community of complex environmental ecosystems, including food samples (Ercolini, 2013). For example, MS technologies have allowed metagenomic analysis of vineyard and wine microbiome deciphering which microorganisms are present with higher sensitivity than previous techniques and how their communities are affected by several magnitude factors (reviewed in Morgan et al., 2017).
In our study, we aim to establish the relationship between the sour rot and Botrytis infection affecting Macabeo grapes with specific changes on the grape microbiota. In order to achieve this objective, sound and damaged grapes were harvested and their microbial diversity monitored during subsequent spontaneous alcoholic fermentations by both culture dependent and independent methods including PCR-DGGE, qPCR and MS to weigh the biases introduced by the techniques in an effort to estimate the community changes introduced by sour rot and Botrytis infection.

 

 

Figure 3. Fermentation density and population dynamics in YPD, Lysine Agar, MRS and GYC medium of (A) healthy, (B) rotten and (C) botrytized grapes fermentations.

Thus, our study is the first to include the molecular techniques qPCR and MS to evaluate the population evolution along spontaneous fermentation of sour rot and Botrytis affected grapes in comparison with healthy grapes. The results showed that the fermentation proceeded the fastest in the rotten must followed by the healthy and the botrytized grapes. As in previous studies, plate cell counts and qPCR results confirmed the increase in the number of both bacteria and fungi in the musts from damaged grapes. MS detected higher biodiversity than the other techniques at each stage, with Saccharomyces and Oenococcus found already in the grape must. Hanseniaspora osmophila replaced to H. uvarum as the predominant yeast during the mid-fermentation stage for both damaged grapes. Furthermore, musts and beginning of fermentation from rotten and botrytized grapes consistently had a higher presence of the fungi Zygosaccharomyces, Penicillium and Aspergillus while high abundance of Botrytis were observed just for botrytized grapes. As expected, the acetic acid bacteria number increased in musts from rotten and botrytized grapes, mostly due to changes in proportion of the genus of acetic bacteria Gluconoacetobacter which remained more abundant during damaged grapes fermentation than during healthy ones. All this mentioned genera have previously been associated with spoiled fermentations and wines. Interestingly, the presence of the lactic acid bacteria Oenococcus oeni at the end of the alcoholic fermentation was strongly affected by the health status of the grapes. This fact indicates that a good health of the grape is mandatory if a successful and spontaneous malolactic fermentation is desired after the alcoholic fermentation.

 

 

Figure 4. Relative abundance of fungal (A) and bacterial (B) taxa detected at > 1% by MS. Taxa that differed significantly (P value <0.05) by fermentation stage (for fungi) or by health status (for bacteria) are indicated by an asterisk.

Figure 5. Alpha diversity graphs showing the PD whole tree index (left) and number of different OTUs (right) for the fungal (a) and bacterial (B) communities determined by MS.

Figure 6. Weighted Unifrac distance PCoA plots for fungal (A) and bacterial (B) communities from Macabeo must and fermentations.

Carmen Portillo started her scientific career with a FPI grant (Spanish Ministry of Education and Science) to perform the PhD at IRNAS-CSIC (2003-2007). During her PhD, she performed two stays at research centers in Norway and The Netherlands. Dr. Portillo postdoctoral experience (more than 10 years total) consists of: two-years (2007-2009) and one-year (2009-2010) contracts as doctor researcher at IRNAS-CSIC, a MEC-Fulbright fellowship of two years at Colorado University (2010-2012), a contract on the private company Abengoa Research (2012-2014), a two years fellowship “Beatriu de Pinos” at URV (2014-2016) and, currently, she is a postdoctoral researcher and PI at URV thanks to a project from the Young Researchers Program, MINNECO. Her current project is based on the use of the “omic” technologies to analyze the microorganisms in wine environments and their relationship with wine quality. (Researcher ID: N-3257-2014).

 

 

References:
Amann, R.I., Ludwig, W., Schleifer, K.H., 1995. Phylogenetic identification and in situ detection of individual microbial cells without cultivation. Microbiol. Rev. 59, 143-169.
Barata, A., Santos, S.C., Malfeito-Ferreira, M., Loureiro, V., 2012. New insights into the ecological interaction between grape berry microorganisms and drosophila flies during the development of sour rot. Microb. Ecol. 64, 416–430.
Barata, A., Seborro, F., Belloch, C., Malfeito-Ferreira, M., Loureiro, V., 2008. Ascomycetous yeast species recovered from grapes damaged by honeydew and sour rot. J. Appl. Microbiol. 104, 1182-1191.
Cocolin, L., Bisson, L. F., Mills, D. A., 2000. Direct profiling of the yeast dynamics in wine fermentations. FEMS Microbiol. Lett. 189:81–87.
Cocolin, L., Campolongo, S., Alessandria, V., Dolci, P., Rantsiou, K., 2011. Culture independent analyses and wine fermentation: an overview of achievements 10 years after first application. Ann. Microbiol. 61, 17-23.
Ercolini, D., 2013. High-throughput sequencing and metagenomics: moving forward in the culture-independent analysis of food microbial ecololgy. Appl. Environ. Microb. 79, 3148-3155.
Fleet, H. G., 2003. Yeast interactions and wine flavor. Int. J. Food Microbiol. 86, 11–22.
González, A., Hierro, N., Poblet, M., Mas, A., Guillamón, J. M., 2005. Application of molecular methods to demonstrate species and strain evolution of acetic acid bacteria population during wine production. Int. J. Food Microbiol. 102, 295-304.
González, A., Hierro, N., Poblet, M., Mas, A., Guillamón, J. M., 2006. Enumeration and detection of acetic acid bacteria by real-time PCR and nested PCR. FEMS Microbiol. Lett. 254, 123–128.
Huber, C., McFadden-Smith, W., Inglis, D., 2011. Management and etiology of grape sour rot in the Niagara region. Phytopathology 101, S259–S259.
Jolly, N.P., Varela, C., Pretorius, I.S., 2014. Not your ordinary yeast: non-Saccharomyces yeasts in wine production uncovered. FEMS Yeast Res. 14, 215–237.
Mateo, E., Torija, M.J., Mas, A., Bartowsky, E. J., 2014. Acetic acid bacteria isolated from grapes of South Australian vineyards. Int. J. Food Microbiol. 178, 98-106.
Millet, V., Lonvaud-Funel, A., 2000. The viable but non-culturable state of wine microorganisms during storage. Lett. Appl. Microbiol. 30:136–141.
Morgan, H. H., du Toit, M., Setati, M. E., 2017. The Grapevine and Wine Microbiome: Insights from High-Throughput Amplicon Sequencing. Front. Microbiol. 8, 820.
Nigro, F., Schena, L., Ligorio, A., Pentimone, I., Ippolito, A., Salerno, M. G., 2006. Control of table grape storage rots by pre-harvest applications of salts. Postharvest Biol. Tec. 42, 142-149.
Nisiotou, A. A., Rantsiou, K., Iliopoulos, V., Cocolin, L., Nychas, G.J.E., 2011. Bacterial species associated with sound and Botrytis-infected grapes from a Greek vineyard. Int. J. Food Microbiol. 145, 432–436.
Rantsiou, K., Urso, R., Iacumin, L., Cantoni, C., Cattaneo, P., Comi. G., Cocolin, L., 2005. Culture-Dependent and -Independent Methods To Investigate the microbial ecology of Italian Fermented Sausages. Appl. Environ. Microb. 71, 1977-1986.
Riberéau-Gayon, P., Dubordieu, D., Donèche, B., Lonvaud, A., 2006. Handbook of Enology. Volume 1. The Microbiology of Wine and Vinifications, second ed. John Wiley & Sons, Ltd, France.
Steel, C. C., Blackman, J. W., Schimdtke, L. M., 2013. Grapevine Bunch Rots: Impacts on Wine Composition, Quality, and Potential Procedures for the Removal of Wine Faults. J. Agr. Food Chem. 61, 5189−5206.
Stefanini I., Albanese D., Cavazza A., Franciosi E., De Filippo C., Donati C., Cavalieri, D., 2016. Dynamic changes in microbiota and mycobiota during spontaneous ‘Vino Santo Trentino’ fermentation. Microb. Biotechnol. 9, 195–208

 

 

Posted by in Enology, Viticulture

4 tips for a picnic with wine

Holidays is time of celebrating life with family and friends. Who doesn't love picnics? Imagine a lovely sunny day in the company of amazing people in a beautiful park. The meal composed by healthy food, water and wine. It doesn’t matter the wine type, it is your choice according with your preference, if consumed with moderation. To carry the bottles there is now good solutions in the market as KOVOT 9 Piece Wine Travel Bag or Insulated Travel Wine Tote Bag. Remember that open a bottle must be an easy thing, with Oster Rechargeable and Cordless Wine Opener with Chiller you can always cause a good impression, because you can open a lot of bottles on a single charge and with the thermal stainless-steel wine chiller you will keep wine cold for hours. After the meal you can play with your friends to Wine-Opoly Monopoly Board Game, which is like the classic property game, but with a wine theme. If you have some doubts about wine, you can try to learn the basics with the books already suggested by your Science & Wine blog. Remember to look your email account each Sunday, because Science & Wine blog will continue to publish more posts about wine with scientific validation. Feel free to subscribe the Blog. NICE HOLIDAYS!
Posted by in Curiosities

Red Wines from Northeastern Brazil: An Abundant Source of Biologically Active Phenolics

By Eduardo de J. Oliveira

The São Francisco Valley is an unsuspected and unusual wine-producing site situated in the Northeastern region of Brazil between the states of Pernambuco and Bahia, at latitude 8 to 9° S and longitude 40° W. This location makes it the wine-making region closest to the equator in the world. This region is characterized by a semi-arid climate and high annual temperatures and sun exposure. With low seasonal climate variation, the São Francisco Valley makes use of irrigation practices that allow 2.5 harvest per year on average, while wine-making companies in the South of Brazil manages only one harvest. Some varietal red wines produced in the region include Syrah, Tannat and Cabernet Sauvignon. Also, several sparkling wines are produced in the region, that also cultivates other tropical fruits and table grapes. Currently, the region accounts for about 15% of the Brazilian wine market.

 

Figure 1. The São Francisco Valley region is highlighted in green in the map of Brazil (Source: UNIVASF)

 

We became interested in the red wines from this region because of the alleged relationship between sun exposure and high level of biologically-active phenolic compounds. In a paper published in 2010 (Lucena et al., 2010), our group demonstrated that wines from the São Francisco Valley contain up to 2 times the total phenolic content of red wines in general as reported in the literature, with some wines having up to 5g GAE/L (GAE: Gallic acid equivalents). In the same paper we showed that fractions extracted from these wines by a previously reported solvent partitioning scheme (Ghiselli et al., 1998) could have high radical scavenging properties (as determined by at least two different methods). In some cases, fractions obtained from these wines had radical scavenging activity compared with those of ascorbic acid or even higher activity than Trolox itself (Trolox is a water soluble analogue of Vitamin E used as a positive control in antioxidant assays). An interesting finding of this investigation was the fact that the levels of trans-resveratrol (as determined by high performance liquid chromatography) in these red wines (0.04 to 1.16 mg/L) were on the lower range of what is typically reported in these wine varieties (which is around 1.70 mg/L), but the level of the cis isomer of resveratrol was found to be significantly higher than of the trans isomer (average levels of cis-resveratrol of 2.66 mg/L against 0.45 mg/L for trans-resveratrol). The fact that cis-resveratrol is not as studied as trans-resveratrol regarding its pharmacological properties is probably because the cis isomer is not easily available commercially. However, the differences in the pharmacological profile of the isomers are more quantitative than qualitative in nature, with the cis isomer being more active than the trans-isomer in inhibiting platelet aggregation for example (Bertelli et al., 1996) and less active in its anti-inflammatory properties (Huang et al., 2014). The fact that these wines have such a high content of cis-resveratrol (in some cases 5 times higher than trans-resveratrol levels) may imply that trans-resveratrol is being photoisomerized into the cis isomer by high sun exposure, although wine making techniques (such as stress irrigation) and grape adaptation may also play a role.

 

Figure 2. Concentration - response curves showing the relaxant effect induced by fraction biorelevant phenolic compounds in rat mesenteric artery rings pre-contracted with phenylephrine in presence and absence of functional endothelium

 

Following these interesting results regarding the phenolic composition of red wines from the São Francisco Valley we decided to conduct an “in vivo” study in spontaneously hypertensive rats treated with an ethyl acetate fraction of a Syrah red wine (de Figueiredo et al., 2017). The rationale behind this study was the recent but growing body of evidence demonstrating an involvement of reactive oxygen species (ROS) in the pathophysiology and maintenance of hypertension (Botelho-Ono et al., 2011 and Porpino et al., 2016). This fraction was chemically characterized using liquid chromatography coupled with high resolution mass spectrometry and was shown to contain mainly flavonoids and its glycosides, but also phenolic acids and derivatives, catechins, and anthocyanins. A total of 25 phenolic compounds were identified. The pre-treatment of spontaneously hypertensive rats with this wine fraction (administered by gavage) at doses of 50 and 100 mg/kg for 15 days was able to decrease mean arterial pressure and heart rate as well as decrease serum lipid peroxidation. The fraction at concentrations of 0.01–1000 µg/mL also induced concentration-dependent relaxation of isolated rat superior mesenteric artery rings pre-contracted with phenylephrine and this effect was not attenuated by endothelium removal, demonstrating a vasorelaxant activity that is independent of intact endothelium. This effect is in contrast with results that implicate substances produced in the endothelium as the source of the vasorelaxant activity of flavonoids (Ha et al., 2016) and may be explained by the complex composition of this fraction in which other classes of natural products may be involved in this pharmacological activity. Indeed, both resveratrol (Novakovic, et al., 2006) and quercetin (Rendig, et al., 2001) have been shown to induce endothelium-independent vasorelaxant in human internal mammary and rabbit arteries respectively.
Taken together these results show that red wines from São Francisco Valley have an unusually high phenolic content and functional properties that warrants further research. In addition to sensory properties, the potential health benefits of wines may be a strong marketing opportunity that could also be explored, especially for wines from less known terroirs such as those from São Francisco Valley.

 


Eduardo de J. Oliveira (Oliveira, E.J.) is is an Assistant Professor at the Department of Pharmacy of Federal University of Vales do Jequitinhonha e Mucurí (UFVJM), at Diamantina, MG, Brazil. He joined UFVJM in 2015 after working in the Department of Pharmacy of the Federal University of Paraiba from 2001-2015 (João Pessoa, PB, Brazil). He earned this B.Sc. in 1993 and a Ph.D. in 2001 from the University of Strathclyde (Glasgow, Scotland) where he also held a fellow research assistant position. His main areas of research are in natural products, analytical method development, pharmacology of natural products and hyphenated techniques. He is also an avid astrophotographer in his spare time.

 

References:

Botelho-Ono MS, Pina HV, Sousa KHF, Nunes FC, Medeiros IA, Braga VA. Acute superoxide scavenging restores depressed baroreflex sensitivity in renovascular hypertensive rats. Auton Neurosci. 2011, 159(1-2): 38–44.
Ghiselli A, Nardini M, Baldi A, Scaccini C. Antioxidant activity of different phenolic fractions separated from an Italian red wine. J Agric Food Chem. 1998, 46(2): 361–367.
Ha SK, Park HY, Ryu MR, Kim Y, Park Y. Endothelium-Dependent Vasorelaxant Effects of Dealcoholized Wine Powder of Wild Grape (Vitis coignetiae) in the Rat Thoracic Aorta. Evid Based Complement Alternat Med. 2016, 2016: Article ID 6846084, 6 pages, 2016. https://doi.org/10.1155/2016/6846084.
Huang TT, Lai HC, Chen YB, Chen LG, Wu YH, Ko YF, Lu CC, Chang CJ, Wu CY, Martel J, Ojcius DM, Chong KY, Young JD. cis-Resveratrol produces anti-inflammatory effects by inhibiting canonical and non-canonical inflammasomes in macrophages. Innate Immun. 2014, 20(7):735-50.
Lucena PS, Nascimento RJB, Maciel JAC, Tavares JX, Barbosa-Filho JM, Oliveira EJ. Antioxidant activity and phenolics content of selected Brazilian wines. J Food Compos Anal. 2010, 23(1):30-36.
Novakovic A, Gojkovic-Bukarica L, Peric M, Nezic, D, Djukanovic B, Markovic-Lipkovski J, Heinle H. The mechanism of endothelium-independent relaxation induced by the wine polyphenol resveratrol in human internal mammary artery. J Pharmacol Sci. 2006, 101(1): 85–90.
Porpino SKP, Zollbrecht C, Peleli M, Montenegro MF, Brandão, MCR, Athayde-Filho PF, França-Silva MS, Larsson E, Lundberg JO, Weitzberg E, et al. Nitric oxide generation by the organic nitrate ndbp attenuates oxidative stress and angiotensin II-mediated hypertension: Organic nitrate and hypertension. Br J Pharmacol. 2016, 173(14): 2290–2302.
Rendig SV, Symons JD, Longhurst JC, Amsterdam EA. Effects of red wine, alcohol, and quercetin on coronary resistance and conductance arteries. J Cardiovasc Pharmacol. 2001, 38(2): 219–227.

 

 

Posted by in Chemistry, Enology, Health

Wine books for holidays

By Paula Silva
The main post of last week was about wine aroma. Smelling wine is a complex experience, that goes beyond the olfactive sensation, is a journey that involve all the senses. It brings to our memory precise moments, specific colors, unique textures and amazing flavors. This is the kind of experience when you have a book in your hands. The smell of each page gives to the reader more than knowledge, gives an unforgettable experience. See here the 3 of the most remarkable books about wine. Good choices to learn about wine these holidays.

The Wine Bible 
Karen MacNeil (Workman Publishing)
Karen MacNeil has tasted more than 10,000 wines and visited wine regions around the world, she is an expert in this field. Just like the title says, in this book, you will find fundamental information about wine but also tips, amusing anecdotes, definitions, glossaries, photos, maps, labels, and recommended bottles.

Wine Folly: The Essential Guide to Wine
By Madeline Puckette and Justin Hammack (Avery)
Wine Folly: The Essential Guide to Wine was designed by the creators of WineFolly.com.
This is a book written to help beginners to learn about wine. With a very funny and contemporary style, this book it is important to everyone who wants to know more about:

  • Detailed taste profiles of popular and under-the-radar wines.
  • A guide to pairing food and wine.
  • A wine-region section with detailed maps.
  • Practical tips and tricks for serving wine.
  • Methods for tasting wine and identifying flavors.

The World Atlas of Wine, 7th Edition
By Hugh Johnson and Jancis Robinson (Octopus Publishing)
Written by authors which are a reference in the wine world, this is a wine essential book. Wine reflects the terroir of the region where it is produced. In fact, wine is influenced by geography, climate, soil, grapevine cultivars, and vitivinicultural practices. If one of these factors change, as it is happening with the climate, the wine produced will necessarily have different attributes. When writing this book, the authors considered changes in climate, techniques, fashion and new regulations between 2008 and 2013. Until a new edition it is not released take a look to this book.

 

Posted by in Curiosities

Modulation of wine astringency by mannoproteins –salivary protein/mannoprotein/polyphenol interactions

By Alba Ramos-Pineda, Ignacio García-Estévez, M. Teresa Escribano-Bailón

The oral sensation called astringency is commonly described as drying, roughing and puckering in the mouth epithelia (Gawel et al., 2000). Although the bases of the astringency mechanism are not well understood yet, it is known to be engendered by different classes of astringent compounds and, among them, polyphenols (Bajec and Pickering 2008, Joslyn and Goldstein 1964). Since some polyphenols are able to bind salivary proteins, namely PRPs, they can form insoluble tannin-protein precipitates in the mouth, causing a loss of lubrication and increased friction in the oral cavity, which would explain its astringency (Baxter et al., 1997). This mechanism is thought to be the main responsible of wine astringency. Among polyphenols, flavanols, flavonols and anthocyanins have shown to be able to interact with PRPs and, therefore, they can be considered as astringent compounds. In fact, flavonol glycosides produce a mouth-drying and mouth-coating sensation at very low threshold concentrations (Scharbert and Hofmann, 2005). However, not all astringents cause salivary protein precipitation, evidencing there must be other mechanisms implicated in astringency development. Indeed, other approaches have suggested that astringency could be engendered by activation of specific taste receptors (Tachibana et al., 2004) or even by direct interactions between tannins and oral epithelial cells (Payne et al., 2009). Gibbins and Carpenter (2013) proposed that the complex sensation of astringency could involve multiple mechanisms occurring simultaneously (see Fig. 1): aggregation of salivary proteins, salivary film disruption, decrease in salivary lubrication, receptors exposure and mechanoreceptors stimulation in the oral mucosal epithelium. Nevertheless, since there are no conclusive results, the scientific community is still discussing the different proposed mechanisms that explain this complex phenomenon.

 

Figure 1. Proposed astringency mechanisms: (A) Protein aggregation and complex formation by the interaction between polyphenols and salivary proteins; (B) Astringency development: (I) Free polyphenols and soluble polyphenol–protein aggregates could disrupt the salivary film and reach the pellicle or even activate specific taste receptors; (II) Insoluble aggregates are rejected against salivary film, causing a loss of lubrication and increased friction in the oral cavity. (III) Direct interaction between polyphenols and oral epithelium. Adapted from Ma et al. (2014).

It is widely acknowledged that the astringent sensation can be modulated by several factors, like the presence of acid, sugars, ethanol, and others. Different studies have revealed that several polysaccharide families are able to interact with tannins, so they could reduce astringency by limitation of available proanthocyanidins (García-Estévez et al., 2017). Thus, polysaccharides could be used to improve astringency with an increase of the wine sweetness and roundness. Among wine polysaccharides, mannoproteins represent ca. 35% of total wine polysaccharides (Vidal et al., 2003). Mannoproteins are glycoproteins from the cell wall of the Saccharomyces cerevisiae that can be excreted to the wine during alcoholic fermentation or be released to the wine during yeast autolysis (Ribereau-Gayon et al., 2000). They are considered as protective colloids that protect wine from protein haze (Dupin et al., 2000) and that can prevent tartrate precipitation (Moine-Ledoux and Dubourdieu 2002). The interest of using mannoproteins in winemaking has gradually increased during the last years and different commercial mannoproteins formulates have been developed in order to modify the phenolic composition and the organoleptic properties of wines (Guadalupe et al., 2010).
A recent study has evaluated the effect of the addition of yeast mannoproteins (MP) on the interaction between a flavonol glucoside (quercetin 3-O-glucoside) and human salivary proteins, combining sensory analysis and analytical techniques such as quenching fluorescence, dynamic light scattering (DLS) and isothermal titration calorimetry (ITC). Sensory analysis confirmed the ability of mannoproteins to decrease the astringency elicited by the flavonol. Results obtained with the different analytical techniques indicate the existence of interactions between mannoproteins and flavonols but also between mannoproteins and salivary proteins, suggesting a possible formation of protein/polyphenol/polysaccharide ternary complex that probably affects the astringency perception (Ramos-Pineda et al., 2018).
.

Food Quality Research Team. Grupo de Investigación en Polifenoles (GIP) - Department of Analytical Chemistry, Nutrition and Food Sciences - University of Salamanca (USAL), Salamanca, Spain.
Our research projects are focused on the study of the role of phenolic compounds on quality and stability of food products. The main research topic is related to the impact of the phenolic maturity of red grapes on sensory quality of red wines, namely on color and astringency properties. Recent works aimed to go deepen on the study of the mechanism for astringency development through the use of physical-chemical studies, in order to provide the wine industry (both wineries and oenological industries) with basic knowledge about this complex sensation.
Furthermore, our studies are also related to the analysis and characterization of phenolic composition (mainly flavonoids and phenolic acids) of different food and plant matrices.
Research Group: (Left to right) Rebeca Ferras Charro, Dr Elvira Manjón Pérez, Dr. Montserrat Dueñas Patón, Dr. M. Teresa Escribano Bailón, Dr Ignacio García Estévez, Dr Cristina Alcalde Eon, Alba M. Ramos Pineda, Ana Navarro Martínez.

 

References:

Bajec, M.R. and Pickering, G.J. (2008). Astringency: mechanisms and perception. Critical Reviews in Food Science and Nutrition 48:858-875.
Baxter, N.J., Lilley, T.H., Haslam, E. and Williamson, M.P. (1997). Multiple interactions between polyphenols and a salivary proline-rich protein repeat result in complexation and precipitation. Biochemistry 36: 5566-5577.
Dupin, I. V. S., Stockdale, V. J., Williams, P. J., Jones, G. P., Markides, A. J. and Waters, E. J. (2000). Saccharomyces cerevisiae mannoproteins that protect wine from protein haze: evaluation of extraction methods and immunolocalization. Journal of Agricultural and Food Chemistry 48: 1086-1095.
García-Estévez, I., Ramos-Pineda, A.M. and Escribano-Bailón, M.T. (2018) Interactions between wine phenolic compounds and human saliva in astringency perception. Food and Function 9: 1294-1309.
Gawel, R., Oberholster, A. and Leigh Francis, I. (2000). A ‘Mouth-feel Wheel’: terminology for communicating the mouth-feel characteristics of red wine. Australian Journal of Grape and Wine Research 6:203–207.
Gibbins, H.L. and Carpenter, G.H. (2013). Alternative mechanisms of astringency–what is the role of saliva? Journal of Texture Studies 44: 364-375.
Guadalupe, Z., Martínez, L. and Ayestarán, B. (2010) Yeast mannoproteins in red winemaking: effect on polysaccharide, polyphenolic, and color composition. American Journal of Enology and Viticulture 61: 191-200.
Joslyn, M.A. and Goldstein, J.L. (1964). Astringency of fruits and fruit products in relation to phenolic content. Advances in Food Research 13: 179-217.
Ma, W., Guo, A., Zhang, Y., Wang, H., Liu, Y. and Li, H. (2014). A review on astringency and bitterness perception of tannins in wine. Trends Food Sci. Technol. 40:6-19.
Moine-Ledoux, V. and Dubourdieu, D. (2002). Rôle des mannoprotéines de levures vis-à-vis de la stabilisation tartrique des vins. Bulletin de l’O.I.V, 75: 471-482.
Payne, C., Bowyer, P.K., Herderich, M. and Bastian, S.E. (2009). Interaction of astringent grape seed procyanidins with oral epithelial cells. Food Chemistry 115: 551-557.
Ramos-Pineda, A. M., García-Estévez, I., Dueñas, M., and Escribano-Bailón, M. T. (2018). Effect of the addition of mannoproteins on the interaction between wine flavonols and salivary proteins. Food Chemistry 264:226-232.
Ribéreau-Gayon, P., Dubourdieu, D., Donèche, B. and Lonvaud, A. (2000). Handbook of Enology. Vol. 1. The Microbiology of Wine and Vinifications, 1st ed., Wiley: Chichester, UK, 454 pp.
Scharbert, S., & Hofmann, T. (2005). Molecular definition of black tea taste by means of quantitative studies, taste reconstitution, and omission experiments. Journal of Agricultural and Food Chemistry 53:5377–5384.
Tachibana, H., Koga, K., Fujimura, Y. and Yamada, K. (2004). A receptor for green tea polyphenol EGCG. Nature Structural and Molecular Biology11: 380-381.
Vidal, S., Williams, P., Doco, T., Moutounet, M., & Pellerin, P. (2003). The polysaccharides of red wine: total fractionation and characterization. Carbohydrate Polymers, 54, 439-447.

 

Posted by in Chemistry, Enology, Food Science and Technology

After the very successful joint meeting in 2017 in Porto, Science & Wine is very pleased to continue this event, which will be organized every 2 years. The Organizing Committee invites all to participate in “Science & Wine – The Wine of the Future” at May, 2019 in the Alfândega Congress Centre, Porto, Portugal.

Science & Wine is very pleased to announce the international partner of “Science & Wine 2019 – The Wine of the Future” the International Society of Antioxidants (ISANH). The partnership with ISANH is a very important one, since the main themes for this conference are “Wine Chemistry and Biochemistry/Health” and “Environmental Chemistry”.

The association of moderate wine consumption with beneficial effects on human health and disease prevention, due to polyphenols antioxidant capacity, it is well known. The polyphenolic contents of wine consist in two classes of components, flavonoids and non-flavonoids, and vary greatly with many different factors including the vineyard, the wine processing techniques, soil and atmospheric conditions during ripening, the ageing process, and grape maturation. A well-balanced characterization of the chemical composition and the antioxidant capacity of wine is therefore necessary to determine their health benefits. It is important to evaluate the correlation between antioxidant capacity and total polyphenolic contents, but also between the concentration of each polyphenol compound and its contribution to the antioxidant activity of wine.
Several studies about the chemical composition of winemaking byproducts are being done, which confirmed that those represent low-cost sources of many phenolic compounds, which have potential industrial applications (pharmaceutical, cosmetic, nutritional, or agricultural) due to their strong antioxidant capacity. Winemaking byproducts have also interesting applications in the field of enology, not only, but also because they are responsible for the wines antioxidant properties. Winemaking byproducts application as natural wine additives could represent a sustainable alternative to maximize the exploitation of this valuable agricultural waste as well as to improve the quality of wines, making them more competitive. On other hand, optimization of food processing based on waste decrease has become a mandatory standard within the most developed countries. The European Union Directive 2008/ 98/EC1 stated that “waste prevention should be the first priority of waste management, and that re-use and material recycling should be preferred to energy recovery from waste”. Winemaking is a seasonal activity, and in grape harvesting period a great accumulation of residues is generated. Usually, winemaking byproducts have been sent to distilleries for obtaining ethanol or to be used as fertilizers or biomass. Nevertheless, these activities are usually carried out by external companies representing economic costs for the wine industry. So, finding alternative solutions for the exploitation and valorization of those byproducts, which would involve economic, social, and environmental advantages, will be of the great interest.
For the above, ISANH is very welcome to “Science & Wine 2019 – The Wine of the Future”.

Selected, refereed papers from the 2019 “Science & Wine – The wine of the Future” conference are planned to be published in a special issue of Agricultural and Food Chemistry. Oral and poster presenters at the conference are invited to submit full manuscripts for consideration for inclusion in the special issue. All manuscripts will be subject to the normal process of peer review. The Journal considers publication of manuscripts reporting original research, or manuscripts that support or improve the unity of the overall theme, including reviews and perspectives. All manuscripts must undergo standard peer review procedures and must conform to Journal guidelines. All authors must adhere to the deadlines set for submission and manuscript revision to be published as part of the group. Manuscripts that do not comply with the deadlines may be considered for publication individually.

Posted by in Chemistry, Curiosities, Economy | Marketing, Enology, Food Science and Technology, Health, History, Nutrition, Viticulture

Characterization of the aroma profile of wines by solid-phase microextraction using polymeric ionic liquid sorbent coatings

By Leandro Wang Hantao

Viticulturists and vintner carefully address the chemistry of winemaking (ripening, fermentation, and maturation) to bestow a symphony of unique and pleasant flavors to the final product (Crucello et al, 2018). Aroma is one the main factors contributing to the quality of wine and sets the difference between a vast number of wines and wine styles produced throughout the world (González Álvarez et al., 2011). The volatile organic compounds (VOCs) are a highly complex fraction of wine with more than 1 000 volatile compounds reported so far (Arcari et al., 2017).

 

Multi-faceted analytical methods are required for profiling of wine aroma. For instance, sample preparation comprises nearly 61% of the time spent on a typical chromatographic analysis, being accounted for 30% of sources of error. The use of non-specific sorbent phases in these protocols aims to extract as much chemical information as possible from the sample. In addition, mild isolation conditions are required to avoid extraction artifacts that originate from sample deterioration and / or contamination (Rivellino et al., 2013). These extraction artifacts, if not properly assigned, may induce misleading interpretation of qualitative results. Over the past decade, modern sample processing has relied on equilibrium-based (i.e., non-exhaustive) approaches. For example, headspace solid-phase microextraction (HS-SPME) is a solvent less, equilibrium-based sample preparation technique that combines sampling and sample preparation into a single step, which may be performed relatively fast and under mild extraction conditions. HS-SPME is likely the ideal tool for aroma profiling of wines because it requires minimal sample handling and it bypasses the co-isolation of non-volatile organic compounds.

In the past decades, SPME sorbent materials have been comprised of modified counterparts of polymeric absorbents, such as poly(siloxane), poly(glycol), and poly(acrylate), and solid adsorbents, including poly(divinylbenzene) and activated charcoal (e.g. Carboxen). A recent hallmark was the introduction of ionic liquid-based sorbents as SPME coatings (Zhao, Meng, and Anderson, 2008). Ionic liquids (ILs) are organic salts that exhibit melting points at or below 100°C. This class of materials has gained increased attention because their solvation properties (i.e., selectivity) may be modulated by simple structural modifications to the cation and anion moieties (Ho et al., 2013). Thus, remarkable extractions have been attained using polymeric ionic liquids (PILs) in SPME experiments.
Brazilian winemaking is experiencing profound changes in an effort to improve the quality of grape juice and wines, while proving products with unique signatures. The manuscript entitled “Characterization of the aroma profile of novel Brazilian wines by solid-phase microextraction using polymeric ionic liquid sorbent coatings” described the coupling PIL-based SPME to comprehensive two-dimensional gas chromatography - mass spectrometry (GC×GC-MS) for sensitive and reliable molecular analysis of wine aroma. In addition, our group has developed simple data mining protocols to extract meaningful information from big data by non-expert users. We are eager to continue our research with wines to help small viticulturists and vintners to produce high-quality and unique Brazilian products.

 

Leandro Wang Hantao is an Assistant Professor and joined the Institute of Chemistry (University of Campinas, Brazil) in May 2017. He earned this B.Sc. in 2009 and Ph.D. in 2014 from the University of Campinas. In 2013, he was appointed a visiting scholar position at the University of Toledo (USA). From 2015 to 2017, he held a Scientist position at the Brazilian Nanotechnology National Laboratory. His research interests are focused on analytical and bioanalytical chemistry.

 

References:

Crucello, L. F. O. Miron, V. H. C. Ferreira, H. Nan, M. O. M. Marques, P. S. Ritschel, M. C. Zanus, J. L. Anderson, R. J. Poppi, L. W. Hantao Anal. Bioanal. Chem. (In press). https://doi.org/10.1007/s00216-018-1134-3
González Álvarez, C. González-Barreiro, B. Cancho-Grande, J. Simal-Gándara Food. Chem. 129 (2011) 890-898. https://doi.org/10.1016/j.foodchem.2011.05.040
G. Arcari, V. Caliari, M. Sganzerla, H. T. Godoy Talanta 174 (2017) 752-766. https://doi.org/10.1016/j.talanta.2017.06.074
F. Zhao, Y. Meng, J. L. Anderson J. Chromatogr. A 1208 (2008) 1-9. https://doi.org/10.1016/j.chroma.2008.08.071

 

Posted by in Chemistry, Enology

Does blind wine tasting work? Investigating the impact of training on blind tasting accuracy and wine preference

By Qian Janice Wang and Domen Prešern

Blind wine tasting refers to the practice of tasting a wine without seeing the label, and deducing the grape variety, location of origin, and vintage of the wine based on what one perceives and infers from the glass. Both the Master of Wine (MW) and the Master Sommelier (MS) exam contains elements of blind tasting, perhaps most recently popularised by the 2013 American documentary SOMM which followed four Master Sommelier candidates as they prepared for the examination. But can one actually be trained to deduce a wine’s origins, or is it just nonsense? Over at The Economist data team, Dan Rosenheck (2017) performed an analysis of guesses made at the 2017 Oxford-Cambridge varsity blind tasting match and deduced that most wines were deduced at a rate better than chance. The varsity match, now in its 65th year, is the oldest university based wine competition in the world (Segal et al., 2013). The competition involves blind tasting 12 wines in two flights – one white, one red. Many illustrious names in the British wine trade, including the likes of Oz Clarke, Jasper Morris, and Mark Savage, first cut their teeth at the varsity match.

 

The victorious Oxford team at the 2016 varsity match, with coach Hanneke Wilson in the middle. The two authors are second and third from the left.

Earlier this year, as the Oxford University Blind Tasting Society started their training season, we had a unique opportunity to follow the progress of a group of relatively novice tasters as they went through the intensive five-week training program under the watchful eye of long-time coach and Oxford Companion to Wine contributor, Hanneke Wilson. The study, funded by an American Association of Wine Economists research scholarship, aimed to get a longitudinal view of expertise acquisition over an intense period of blind tasting training, where participants attend multiple tastings a week over a period of 36 days. This allowed us to study both within participant development and group-wide accuracy as a whole (e.g. variance of guesses within a group), as well as track people’s shifts in wine preference. While wine preference is not explicitly a part of the blind tasting match, we believed it is an important question to investigate. Given the rapid rise of knowledgeable wine tasters in developing markets (e.g. China, see Li & Bardaji, 2017), it is crucial to understand how increasing expertise can influence preference for specific wine styles (e.g., less fruit-driven, higher acid, more bottle maturation, etc.). Because the wines were tasted blind, we were be able to track preference for only wine-intrinsic attributes without the participants being biased by the label, price, or origin information (Almenberg & Dreber, 2011; D’Alessandro & Pecotish, 2013; Mueller & Szolnoki, 2010). Over 36 days, we collected a total of 2271 tasting notes and guesses from 15 participants (3 women, 12 men) who participated in 18 tasting sessions. A total of 212 wines were tasted (104 whites, 109 reds) ranging in vintages from 2005-2017, and ranging in price from £7 to £35 (with 75% of the wines between £12 and £18). There were a total of 44 grape varieties (23 white, 21 red), 14 countries, and 44 regions.

The tasting sheet used by participants at each blind tasting session.

We proposed five hypotheses, related to questions of whether and how training can improve blind tasting accuracy, and, from a commercial prospective, how wine preferences change with increased wine-tasting experience.


Hypothesis 1: Training will reduce within group variability in guesses.
We calculated, for each training session, the average number of people who agreed on a guess of grape variety, country, region, and vintage. Over time, we saw a significant increase in the number of people who agreed in their guess for grape variety (remember, everyone tasted the wines in silence and made their guesses individually), and no changes for country, region, or vintage.
Furthermore, we looked at the most common within-group guess of grape variety, country, region, and vintage guess for each wine. As it turned out, the probability of the most common guess being correct was 1) significantly higher than random chance, and 2) significant higher than if they had just guessed the most frequently occurring grape variety, country, region, or vintage.

 

Instances where the most common guess amongst the participants for each wine, by categories of grape variety, country, region, and vintage was in fact the correct one. % of most common guess is compared against chances of being correct simply by guessing the most frequently occurring grape/country/region/vintage. Chi squared test of independence was conducted to compare the accuracy of the most common guess against the baseline condition of occurrence frequency. ** indicates significance at 0.01 level.

Hypothesis 2: Training will make participants more accurate in their guesses.
Pearson’s correlation coefficients between time and the number of accurate answers revealed that grape variety accuracy did increase over time. We did not observe any improvements with regard to country and region guesses, and vintage accuracy actually went down! This might be because in the beginning, people were merely guessing the most recent vintage for all the wines, which tended to be correct. As they became more confident, however, they begun varying vintage guesses which led to more errors.

Hypothesis 3: Training will make participants more accurate in their structural assessment of wines.
With regard to structural elements in the wine, we decided to assess participants’ accuracy in evaluating the acid (low, medium, crisp, high) and alcohol levels (low, medium, high). Over time, we observed that participants gradually went from underestimating acidity to overestimating acidity, but with the net effect of increasing accuracy over time. In terms of alcohol levels, we did not observe any significant changes in accuracy over time. However, it should be kept in mind that for both acidity and alcohol, error levels (in terms of %) were not significantly different from 0! (In other words, people are pretty good at discerning wine structure).

Hypothesis 4: Training will change the way participants write tasting notes, leading to the usage of more specific descriptors and a different body of vocabulary.
One interesting result that came out of our tasting note analysis was that tasting notes for the more preferred wines were significantly longer (by 23%) than for the less preferred wines! We did not observe a difference in the length of tasting notes or the size of vocabulary pool over the training session, although those with prior experience (e.g. returning team members) wrote longer tasting notes than those without prior experience.

 

Plots showing accuracy of acidity (A) and alcohol (B) estimations over time. Error bars indicate the standard error of the mean.

Hypothesis 5: Training will change the tasters’ wine preference, leading them to prefer less fruit-forward and/or more structured wines.
This was probably the most interesting finding from our study. Overall, wine preference was positive correlated with wine age, acidity, sweetness, and colour (red wine was preferred to white). Over time, we observed a shift in preference towards older wines, and a decrease in the importance of wine colour. Those with little initial blind tasting training also experienced a change in preference towards greater acidity and alcohol, and decreased their preference for oak.

In conclusion, over the 36-day training period, we observed an increase in accuracy and within-group agreement in terms of grape variety guesses. Moreover, the most commonly guessed grape, country, region, and vintage were all more accurate than chance. Structurally, acidity assessment accuracy improved, although error margins for both acidity and alcohol were not significantly different from zero. Finally, with training, there was a shift in wine preference towards more mature and structured wines, which has important implications for growing wine markets with an increasingly educated consumer population.
Those interested in a longer length report can download the working paper at http://www.wine-economics.org/aawe/wp-content/uploads/2018/06/AAWE_WP230.pdf

Qian Janice Wang is an Experimental Psychologist currently working as a postdoctoral researcher at the Crossmodal Research Lab at Oxford University. Her research examines crossmodal correspondences between flavour and the senses of sight, sound, and touch; with a special focus on how auditory stimuli can modify and enhance the way we perceive food and drink. She has 24 peer-reviewed publications and her work has been featured in the Financial Times, The Economist, The Telegraph, National Post Canada, Le Figaro, Purple Pages, and la Revue du Vin de France, amongst others.

Domen Prešern is a current PhD student in Theoretical Chemistry at Oxford University. He uses supercomputers to study mechanical and thermodynamical properties of complex DNA (origami) structures.

Domen is the current president of the Oxford University Blind Tasting Society, and Janice was the president of the Oxford University Blind Tasting Society from 2015-2017. Between them, they have lead the Oxford Varsity blind tasting team three times to victory against Cambridge. Domen and Janice are both currently studying for their WSET Diploma and have both completed the WSET Educator training course. They post about wine under @DQPWines on twitter and instagram.

 

References:
Almenberg, J., & Dreber, A. (2011). When does the price affect the taste? Results from a wine experiment. Journal of Wine Economics, 6, 111-121.
D’Alessandro, S. & Pecotish, A. (2013). Evaluation of wine by expert and novice consumers in the presence of variations in quality, brand, and country of origin cues. Food Quality and Preference, 28, 287-303.
Li, Y., & Bardaji, I. (2016). A new wine superpower? An analysis of the Chinese wine industry. American Association of Wine Economists Working Paper, June 2016, 198.
Mueller, S., & Szolnoki, G. (2010). The relative influence of packaging, labelling, branding and sensory attributes on liking and purchase intent: Consumers differ in their responsiveness. Food Quality and Preference, 21, 774-783.
Rosenheck, D. (2017). Think wine connoisseurship is nonsense? Blind-tasting data suggest otherwise. The Economist, August 17th. Accessed from https://www.economist.com/blogs/graphicdetail/2017/05/daily-chart-11.
Segal, J., Pol Roger UK Ltd, & Waugh, H. (2013). Red, Whites & Varsity Blues: 60 Years of the Oxford & Cambridge Blind Wine-Tasting Competition. London, UK: Pavilion Books.

 

Posted by in Enology