Manganese levels in wine
Mapping pepper
Beating Brett
Secrets of solids
Shiraz symposium
Riverland Roadshow breaks record
Allergen assistance available
Information packs help you find what you need
Time to catch up on webinars?
Recent literature
Manganese levels in wine
As has been widely reported, the Chinese government recently enforced mandatory upper limits on copper (1 mg/L), iron (8 mg/L) and manganese (2 mg/L) in wine. While the typical levels and impacts of iron and copper are well established, manganese levels in wine are less well understood, although at the levels analysed, are not believed to pose any health or quality issues. Since the introduction of the limit, the AWRI has analysed the manganese levels of more than 800 wines and some important trends in the data have been observed.
Firstly, the distribution of results was consistent for all wines irrespective of origin. This suggests that manganese levels in wine are common worldwide. Secondly, a significant number of wines exceeded the 2 mg/L limit, with higher manganese levels seen in red wine than in white wine. This may be due to the extraction process during the fermentation of red wine releasing more manganese from the grape skins and flesh. No significant differences were seen among varieties of red and white grapes; however, there does appear to be a vintage-to-vintage variation, with the median values for the 2011 season being significantly lower than those for 2009 and 2013. The median values for 2010 and 2012 fell between these two groups.
Manganese occurs naturally in soils and grapes; however one published study from Sicily (La Pera et. al. 2008) found that certain manganese-based fungicide treatments could significantly increase the concentration of manganese in wine. It should, however, be noted that the AWRI has analysed wines which exceeded the limit which have not received any such fungicide treatments. The impacts of manganese-containing viticultural products are still to be confirmed in the Australian context.
The AWRI has also tested a number of wine fining treatments for their effects on manganese concentration. To date, none tested has shown a satisfactory impact on reducing the manganese concentration of wine. Work is continuing to assess a range of other possible processing and fining options. In the mean time, the current recommendation is that all wines destined for export to China should be tested for copper, iron and manganese at one of the laboratories offering this service.
For more information, contact Dr Eric Wilkes, Group Manager Commercial Services, eric.wilkes@awri.com.au or 08 8313 6600.
Reference
La Pera, L., Dugo, G., Rando, R., Di Bella, G., Maisano, R., Salvo, F. (2008). Statistical study of the influence of fungicide treatments (mancozeb, zoxamide and copper oxychloride) on heavy metal concentrations in Sicilian red wine. Food Additives & Contaminants: Part A, 25(3), 302-313.
Mapping pepper
For the first time, the distribution of the ‘pepper’ compound rotundone has been mapped in a Shiraz vineyard. Results recently published in the Australian Journal of Grape and Wine Research highlighted a surprisingly wide concentration range of rotundone in grapes across the block. The study showed clearly the large spatial variability of the compound and that it is linked to differences in soil characteristics and topography. The topographical variation pointed towards temperature and/or solar radiation effects being involved, rather than vine vigour.
The rotundone level was measured in grape berry samples from 177 vines within a 6.1 ha block in the Grampians, a region known for producing wines of ‘peppery’ character. The results were mapped and overlaid with other map layers showing variation in soils, topography and vine vigour.
This is believed to be the first study of within-vineyard spatial variability of a key grape-derived flavour compound. It highlights the potential opportunity to use selective harvesting or targeted viticultural manipulation as a means of influencing wine style – in this case the ‘pepperiness’ of Shiraz. The study was conducted with Dr Rob Bramley of CSIRO Ecosystem Sciences and the late Nathan Scarlett of Rathbone Wine Group.
A copy of the article can be ordered online here or by contacting infoservices@awri.com.au.
Beating Brett
Several new resources on Brettanomyces have just been added to the AWRI website, bringing together knowledge from researchers and the AWRI helpdesk team. First up is a new fact sheet which provides up-to-date advice on controlling Brett in the winery. Next there’s a comprehensive list of frequently asked questions about Brett – if you can think of a question that hasn’t been covered, get in touch and we’ll add it to the list. Finally, there’s a new information pack of published papers and other resources relevant to Brett spoilage. Wines are most vulnerable to Brett growth around the end of malolactic fermentation before SO2 is added, so stay vigilant!
Secrets of solids
Fermenting white juices containing high levels of grape solids can result in increased hydrogen sulfide production during primary fermentation. However, excessively clarifying juices may result in attenuated or stuck primary or malolactic fermentations resulting in elevated levels of volatile acidity. Well so says Winemaking 101.
While there is a lot to be said for Winemaking 101, previous work by the AWRI has revealed that fermenting on grape solids also results in significantly more polysaccharides in white wines – more than extensive skin contact, using pressings, and even more than (what many may consider a radical practice of) partially fermenting white juice on skins. Higher levels of polysaccharides are thought to positively contribute to white wine mouth-feel, and to enhance both protein and cold stability resulting in less bentonite fining and lower refrigeration costs.
While juices will naturally clarify under the action of gravity given time, vintage logistics dictate that the settling process be achieved as quickly as possible (“We have plenty of time – it’s vintage” is a phrase never said). Typically faster clarification is achieved by adding pectolytic enzymes, which within minutes, ‘mulch down’ the juice polysaccharides that inhibit settling. Alternatively, settling can be sped up by adding bentonite as its charged surface helps to agglomerate grape solids into heavy particles that precipitate more easily.
In a new project, the AWRI is investigating the effect of different types of juice clarification (natural settling, enzyme- and bentonite-assisted settling) on the macromolecular composition of white wine. The effects of the method of clarification and the time taken to achieve various levels of clarity on the polysaccharide, protein and phenolic composition are being investigated now. Industry partners are being sought to participate in a winery-scale project in 2015.
For more information or to express interest in being involved in the 2015 trial, please contact Richard Gawel, richard.gawel@awri.com.au or 08 8313 6600.
Shiraz symposium
A one-day Symposium exploring the latest developments and innovations in cool climate Shiraz production will be presented by the AWRI and Wine Victoria in Melbourne on 11 June. The Symposium will include insights into international Shiraz production, technical presentations on flavour characters, case studies on Shiraz winemaking and a tasting of memorable cooler climate Shiraz wine styles.
The full program for the day can be accessed here. Bookings are essential, and can be made using the online registration and payment form.
| When: | Wednesday, 11 June, 2014, 9.20 am – 4.30 pm |
| Where: | The William Angliss Institute, Auditorium, 555 La Trobe Street, Melbourne |
| Registration cost: | $99.00 including GST |
For more information about the Symposium, please contact Mark Krstic on 0437 325 438 or mark.krstic@awri.com.au.
Riverland Roadshow breaks record
A record-breaking crowd of 81 people attended the AWRI’s Roadshow seminar in Renmark last week. AWRI Researchers were joined by Dr Mike McCarthy from SARDI and Dr. Jason Smith from NGWIC in presenting topics covering irrigation, clones, grapevine nutrition, post-harvest management and managing phenolics quality. A lively interactive session was a highlight of the day. The next region to be visited by the Roadshow team is Queensland – so the challenge is now on to the Queensland industry to set a new record!
Allergen assistance available
Allergies to wine are extremely rare; however certain countries including Australia include allergen warnings on the label of wines and wine products. It’s therefore important for wine producers to understand which processing aids may result in allergen residues as well as the rules on allergen labelling for different countries. The AWRI’s Wine allergen portal provides a comprehensive and up-to-date collection of online resources related to allergens in wine for consumers and producers.
AWRI Commercial Services also provides an allergen testing service.
If you have any questions about allergens in wine, please contact Creina Stockley on 08 8313 6600 or creina.stockley@awri.com.au.
Information packs help you find what you need
Are you looking for the latest grape and wine information? A new page on the AWRI website lists information packs with up-to-date resources on a range of useful topics. Each pack contains reference lists and fact sheets on the particular topic. Articles can be easily ordered online from the AWRI Library. Topics include: heat and cold stability, making lower alcohol wines, emerging varieties and measures of quality from vineyard to winery.
Time to catch up on webinars?
Since 2012, the AWRI has hosted more than 35 webinars on topics including: canopy management, hybrid yeast, alternatives to bentonite, rootstocks, oxygen management during winemaking and dealing with frost. If you missed a webinar when it was broadcast, you can still watch it at a time of your choice by accessing the recordings on the AWRI website. Recordings of the 2012 webinars and 2013 webinars are available. You will need to enter your name and email address for access, and you may need to download a small piece of software called a codec to allow the recordings to play on your computer. If you have any difficulties accessing the recordings, please contact Michael Downie on 08 8313 6600 or infoservices@awri.com.au.
Recent literature
The John Fornachon Memorial Library at the AWRI delivers journal articles and loans books to Australian grapegrowers and winemakers. Publications can be searched and requested via the Library catalogue – or you can email the AWRI with your request. A list of recent AWRI publications follows.
- To order AWRI staff publications and articles from Technical Review please contact the Library.
- Articles and books on specific topics can be searched for and ordered via the Library catalogue
- To request a Literature search on a specific topic contact the Library via email or telephone (08) 8313 6600.
Recent AWRI staff publications
1597 Mayr, C.M., Parker, M., Baldock, G.A., Black, C.A., Pardon, K.H., Williamson, P.O., Herderich, M.J., Francis, I.L. Determination of the importance of in-mouth release of volatile phenol glycoconjugates to the flavor of smoke-tainted wines. J. Agric. Food Chem. 62 (11): 2327-2336; 2014.
1598 Scrimgeour, N., Wilkes, E. Closure trials show volatile sulfur compound formation can still cause a stink. Aust. N.Z. Grapegrower Winemaker (602): 62, 64-67; 2014.
1599 Coulter, A. Ask the AWRI: Can ‘Brett’ affect white wines? Aust. N.Z. Grapegrower Winemaker (602): p.54; 2014.
1600 Dry, P. Souzao. Wine Vitic. J. 28 (2): p. 60; 2014.
1601 Krstic, M., Barlow, S. Vintage 2030 and beyond: Producing quality wines in warmer times. Wine Vitic. J. 28 (2): 52-57; 2014.
1602 Smith, P., Bindon, K., McRae, J., Kassara, S., Johnson, D. Tannin: impacts and opportunities along the value chain. Wine Vitic. J. 28 (2): 38-41; 2014.
1603 Cordente, A.G., Cordero-Bueso, G., Pretorius, I.S., Curtin, C.D. Novel wine yeast with mutations in YAP1 that produce less acetic acid during fermentation. Fems Yeast Res. 13 (1): 62-73; 2014.
1604 Uberti, F., Danzi, R., Stockley, C., Peñas, E. Ballabio, C., Di Lorenzo, C., Tarantino, C., Restani, P. Immunochemical investigation of allergenic residues in experimental and commercially-available wines fined with egg white proteins. Food Chem. 159: 343-352; 2014.
1605 Capone, D.L., Herderich, M.J., Pardon, K.H., Hayasaka, Y., Cordente, A.G., Grant-Preece, P.A., Sefton, M.A., Elsey, G.M., Jeffery, D.W. Formation of varietal thiol aroma compounds in wine: Synthetic and analytical studies of grape and wine thiol conjugates. In Hofmann, T., Meyerhof, W., Schieberle, P. (eds) Advances and Challenges in Flavor Chemistry and Biology: Proceedings of 9th Wartburg Symposium on Flavour Chemistry and Biology, Eisnach, Germany Deutsche Forschungsanstalt für Lebensmittelchemie: Freising, Germany 242-248; 2011.
1606 Mateo, E., Torija, M.J., Mas, A., Bartowsky, E.J. Acetic acid bacteria isolated from grapes of South Australian vineyards. Int. J. Food Microbiol. 178: 98-106; 2014.
1608 Taylor, A., Day, M.P., Hill, S., Marshall, J., Patriarca, M., White, M. Atomic spectrometry update: Review of advances in the analysis of clinical and biological materials, foods and beverages. Journal of Analytical Atomic Spectrometry 29 (3): 386-426; 2014.
1609 Borneman, A.R., Zeppel, R., Chambers, P.J., Curtin, C.D. Insights into the Dekkera bruxellensis genomic landscape: Comparative genomics reveals variations in ploidy and nutrient utilisation potential amongst wine isolates. PLoS Genetics 10 (2): e1004161; 2014.
1610 Scarlett, N.J., Bramley, R.G.V., Siebert, T.E. Within-vineyard variation in the ‘pepper’ compound rotundone is spatially structured and related to variation in the land underlying the vineyard. Australian Journal of Grape and Wine Research DOI: 10.1111/ajgw.12075: 9 p.; 2014.
1611 Mayr, C., Geue, J., Holt, H., Pearson, W., Francis, I.L. Characterization of the key aroma compounds in Shiraz wine by quantitation, aroma reconstitution, and omission studies. J. Agric. Food Chem. DOI: 10.1021/jf405731v: 36 p.; 2014.
1612 Dry, P. Ask the AWRI: Bunches with ripe and unripe berries. Aust. N.Z. Grapegrower Winemaker (603): p.49; 2014.
1613 Essling, M. The role of potassium in grapevine function. Aust. N.Z. Grapegrower Winemaker (603): p.74; 2014.
1614 Contreras, A., Henschke, P., Chambers, P., Curtin, C., Varela, C. New yeast approach is aiming to produce a lower alcohol wine. Aust. N.Z. Grapegrower Winemaker (603): 82-83; 2014.
1615 Kutyna, D.R., Cordente, A.G., Varela, C. Genetic engineering of industrial Saccharomyces cerevisiae strains using a selection/counter-selection approach. Mapelli, V. (ed.) Yeast metabolic engineering: methods and protocols. Totowa, N.J.: Humana Press. Chapter 9: 157-168; 2014.
Disclaimer
The material contained in this publication is comment of a general nature only and is not and nor is it intended to be advice on any specific technical or professional matter. In that the effectiveness or accuracy of any technical or professional advice depends upon the particular circumstances of each case, neither the AWRI nor any individual author accepts any responsibility whatsoever for any acts or omissions resulting from reliance upon the content of any articles. Before acting on the basis of any material contained in this publication, we recommend that you consult appropriate technical/professional advisers.