eNews


eNews – January 2013

Above average bushfire potential this Summer: be prepared
Slow or stuck ferment? Easy steps to take
Restrictions on diuron use in vineyards
Is there Brett in your winery? Get the AWRI on the case
App appeals for smart agrochemical searching
Assisting consumers’ choice of Chardonnay
GWRDC and AWRI agree to develop a new Investment Agreement
AWRI providing quality assurance for Wine Australia
OIV’s good fining practice for allergens
Events not to be missed in 2013
ASVO Fellowship honours Peter Dry
Recent literature

Above average bushfire potential this Summer: be prepared

The Bureau of Meteorology has predicted above average chances the summer 2012/2013 maximum temperature will exceed the long-term median maximum temperature over far northern Australia, southern and western WA, southern SA, southern NSW, Victoria and Tasmania (Anon 2012a). The abundant grass growth from the high amount of rain from two strong La Niña events seen in the past two years means vast parts of Australia face above-average bushfire potential this bushfire season (Anon 2012b).

Given the effect of bushfires on winegrowing regions, it would be prudent to start thinking about what you would need to do if your vineyard becomes covered with smoke.

One of the biggest concerns regarding smoke in the vineyard is “will my grapes and wine be affected by smoke taint?” Of course, testing grape samples for smoke-taint marker compounds is a good place to start and the AWRI has recently developed volatile phenol and phenol glycoside analyses to do this.

Analyses of volatile phenols and phenol glycosides conducted at the AWRI on non-smoke-affected grapes and wines have greatly improved our ability to determine whether grapes have been exposed to smoke. The results of the volatile phenol analysis on grapes suspected of smoke exposure, combined with knowledge of typical ‘background’ levels, can help winemakers conduct a risk assessment of the potential for producing a smoke-tainted wine. However, whilst low and high levels of volatile phenols and their precursors are relatively easy to interpret (i.e. not smoke-affected and smoke-affected, respectively), it is more difficult to interpret what effect ‘intermediate’ levels of these compounds will have on the sensory profile of a finished wine.

Mini fermentations

Given the lack of data available to determine the correlation between the levels of smoke-taint ‘marker’ compounds and the intensity of smoke taint aroma and flavour, the AWRI recommends that laboratory-scale, or ‘mini ferments’ be performed in an attempt to better understand the sensory impact of smoke-exposed grapes on the final wine. Analysis of the wine produced from these ‘mini ferments’ can also be performed in order to link sensory observations with smoke compound measurements.

The AWRI has developed a basic fermentation protocol which is available on the AWRI website. Winemakers can use this method, followed by sensory assessment of the wine produced, to gauge the potential risk of any smoke taint that might arise from use of grapes that have been exposed to smoke. Whilst the method is not overly complicated, some care must be taken when following the method, as the wine produced needs to be subjected to a sensory assessment. Consequently, some additions might need to be made during the process, so it would be beneficial to review the method before vintage to become familiar with the procedure and the solutions that might be required for making additions. It is worthwhile obtaining some fermentation vessels so they are close at hand if they become necessary. Vessels such as Décor 3L plastic containers (or similar) are ideal and are available from most supermarkets. Other materials, such as yeast, PMS, DAP, tartaric acid, pectic enzyme and copper are usually readily available during vintage.

Note that when assessing the wine produced from the ‘mini ferment’, it is best that more than one person assess the wine, as sensitivity to smoke-taint characters varies greatly from person to person. In addition, the wine should be assessed carefully, as a high level of fermentation esters might make it more difficult to identify any smoke-taint characters that might be present.

Any queries?

The AWRI’s winemaking and viticulture specialists are available to help Australian wine and grape producers: call 08 8313 6600 or email winemakingservices@awri.com.au.

References:
Anon (2012a) National seasonal temperature outlook: probabilities for Summer 2012/2013. Australian Government Bureau of Meteorology. [http://www.bom.gov.au/climate/ahead/temps_ahead.shtml]

Anon (2012b) Grass will again pose the biggest fire risk this Summer. Bushfire CRC.
[http://www.bushfirecrc.com/news/news-item/grass-will-again-pose-biggest-fire-risk-summer]

Slow or stuck ferment? Easy steps to take

A slow or stuck ferment is a challenge a winemaker will face at some stage of their career. The AWRI’s Winemaking Services team has had 650 queries over the last 15 years regarding ways to restart a stuck ferment, with queries generally doubling during years when we experience heatwaves during harvest. Here are easy steps for a winemaker to take to get that fermentation going.

How do you know your ferment is slowing down or stuck? The best way is to monitor the fermentation twice daily for Baume or Brix, and temperature, and to plot this as a fermentation curve (a graph template is available for Australian winemaker use via password on the AWRI website). These measurements will identify when ferments begin to slow down, and before it has stopped, so that proactive action can be taken. The fermentation curves can also be used to establish if temperatures are becoming too cool or too warm for the ferment.

If the ferment is slowing down:

  1. Try warming the ferment up if too cold, or cooling down if it’s getting hot. Yeast like the temperature to be kept relatively stable and, in general, do not function well at temperatures >32°C for reds or <15°C for whites.
  2. If a natural ferment is slowing down, or a difficult ferment is suspected, then it is best to use an inoculated yeast.
  3. If the yeast are not that active, or are settling to the bottom of the tank, try some agitation during the initial stage of the ferment; check for budding and/or viability by vital (e.g. methylene blue) staining.
  4. Aerating once fermentation has started can also help the yeast build strong cell walls for ethanol tolerance to prevent the ferment becoming stuck; there is no risk of oxidising the wine while yeast are active. Aeration is a powerful fermentation stimulant when used correctly.
  5. If the ferment is slow from the outset, make sure the ferment isn’t slowing due to any fermentation inhibitors including:
    • high sulfite concentrations in the must;
    • high volatile acidity from native microorganism growth/check for high bacteria count;
    • high Baume/Brix content. Some yeast are not tolerant to excessive sugar levels. Correspondingly some yeast don’t cope well in ethanol concentrations >15%;
    • agrochemical residues. Grapes harvested within withholding periods can contain some metals, sulfur or other compounds that can stress the fermentation yeast;
    • chlorine from water used during yeast hydration; and
    • very low pH (typically early harvest whites); some yeast cannot tolerate pH of 3.0 or less, especially when sulfite is present.

    For some inhibitors such as high sulfite, a sacrificial yeast addition, or inoculation at twice the usual inoculum can be successful. Ensure the yeast have been strongly aerated to ensure aldehyde production which binds the excessive sulfite.

  6. If the ferment is slow, or starting to produce sulfides, then nutrients might be an issue; particularly in highly clarified juice, or wines with some native microorganism growth. Measure the yeast assimilable nitrogen (YAN) level and make an addition if in the early stages of fermentation. If DAP doesn’t prevent sulfides, other nutrients such as vitamins or complex nutrients (e.g. inactive yeast products) can be tried. If sulfides persist, it might be coming from agrochemicals such as elemental sulfur.
  7. Addition of yeast hulls, fresh yeast lees from a recently finished ferment, or addition to an active fermentation can help a struggling ferment go through to dryness.
  8. Re-inoculate a slow ferment using strong fermenting and alcohol tolerant yeast.
  9. If the re-inoculation is not successful then try the re-inoculation using a culture or scale-up (step-wise acclimatisation) restart procedure (available on the AWRI website).
  10. If all else fails, call the AWRI’s Winemaking Services help desk (08 8313 6600).

Restrictions on diuron use in vineyards

After a major review of diuron by the APVMA, this herbicide is no longer registered for use in a large range of crops including grapes. The decision is based on toxicological and environmental findings obtained in the review. The implication for grape growers is that until 28 November 2013, the diuron products listed in the 2012/2013 Agrochemicals registered for use in Australian viticulture (aka ‘the Dog Book’) are permitted under APVMA permit 13874 to be used in accordance with the label instructions so long as they meet the permit conditions. After this date, diuron will no longer be permitted for use in viticulture. More information about the conditions outlined in the permit, are available in the AWRI’s agrochemical update issued in December 2012.

Is there Brett in your winery? Get the AWRI on the case

In most wineries there is a constant background presence of Brettanomyces yeasts. Avoiding wine spoilage requires ongoing sanitation procedures, appropriate wine storage conditions and monitoring regimes. The AWRI provides a service to detect the presence of Brett in wine and in your winery.

Brett spoilage typically occurs in red wine stored in barrel, and can be a very slow process. Crucial to product quality is monitoring for the presence of Brett in wine as well as implementing changes in processes to manage/reduce its presence and spread before it becomes a major problem. The AWRI is offering a Brett service which encompasses the detection of ‘Bretty’ compounds in wine, as well as for the presence of live Brett strains in your wines. As an extended service, the AWRI can also determine if the live strains are likely to be sulfite resistant, and can conduct an audit to detect the presence or absence of Brett throughout your winery.

Please contact Dr Tina Tran for further information.

App appeals for smart agrochemical searching

The ‘Agrochemicals registered for use in Australian viticulture’ booklet (aka the ‘Dog Book’) and online database have been supporting grape and wine producers in the management of pests and diseases for many years. In November, the AWRI launched the ‘AWRI Agrochemical Search’ app designed to work on Apple’s iOS platforms and Android. Now the Dog Book is easily searchable via your smart phone or tablet.

Some key features of the app include:

  • A full list of pests and diseases (some of which are not available in the printed ‘Dog Book’); and
  • Notifications to your device for new data updates.

Once the app is installed on your smart phone or tablet, you can access the agrochemical database offline (i.e. internet connection is not required; any updates are automatically made to your smart phone or tablet when internet connection is re-established).

The app is free and is available for download in iTunes or Google Play. For further information, please contact the AWRI by email or by telephone: 08 8313 6600.

Assisting consumers’ choice of Chardonnay

Following the success of the PinotG Style Spectrum and many approaches from a broad sector of the Australian wine industry, the AWRI is seeking partners to develop a similar labelling device for Chardonnay wines. Planning for the program is well underway, with the deadline for companies to nominate their participation being 28 March 2013, with the final decision to proceed depending on the level of industry commitment at that date. It is envisaged that the analysis and labelling device will be available from vintage 2014.

The PinotG Style Spectrum uses advanced analytical fingerprinting techniques to classify Pinot Gris and Pinot Grigio wines on a linear scale between the anchor words ‘crisp’ and ‘luscious’ (for further information see the AWRI website and the PinotG website). While classification is done using spectral fingerprinting, the underlying scale was developed through extensive sensory assessment of a broad range of Australian and international Pinot G wines by industry and AWRI panels.

For Chardonnay, different anchor words will be developed in consultation with an industry working group and a consumer tasting panel, but the implementation will be the same and will leverage on the experience gained in developing the PinotG Style Spectrum. This will involve development of a labelling device featuring a simple scale which allows the consumer to identify quickly where in the Chardonnay Style Spectrum the wine sits, allowing them to make an informed purchase decision.
For more information and to receive the expression of interest document please contact Eric Wilkes.

GWRDC and AWRI agree to develop a new Investment Agreement

The GWRDC invests in the AWRI through an Investment Agreement linked to the Seven Year Research, Development and Extension Plan. In 2012, the GWRDC commissioned an evaluation of the Investment Agreement. The AWRI submission to the Review Committee, Independent economic assessment, stakeholder input and the review report, are available at the AWRI’s website. The review findings led to the announcement of a new Investment Agreement between GWRDC and AWRI, which will be developed over the coming months and take effect from 1 July 2013.

AWRI providing quality assurance for Wine Australia

With heightened concerns around agrochemical residues around the world, Wine Australia is keen to ensure that Australian wines are consistent with international best practice and compliant with all international regulatory requirements. Following the introduction of a new system of auditing wineries and exporters, Wine Australia has chosen AWRI Commercial Services to provide high quality analysis for a range of agrochemical residues and other trace analytes. The AWRI Commercial Services is able to provide a large simultaneous screen of more than 50 major registered agrochemicals at levels at or below the lowest maximum residue limit (MRL) of any export destination.

AWRI Commercial Services will be working with Wine Australia to ensure the quality of Australian wines remains high and meet stringent regulatory requirements for all overseas markets.

In confirming the contract, Steve Guy from Wine Australia said, “We engaged the AWRI not only because they are capable of performing the services we require but also because they are responsive, flexible and eager to exceed expectations.”

OIV’s good fining practice for allergens

Are you confident that the winemaking process you use to fine your wines removes all potential proteins from a food allergen from your wine?The OIV has recently published a working document for winemakers on its website called Good fining practice guidelines for wine to be applied after the use of proteinaceous [allergenic] wine fining agents [casein and egg white].

This working document was developed by the OIV Taskforce on Allergens to supplement and support the OIV-developed criteria for the methods of quantification of potentially allergenic residues of fining agent proteins in wine (OIV-MA-AS315-23) which the European Union refers and defers to in its documentation on allergens and allergens labeling.

This working document summarises detailed information and arguments regarding:

  1. the definition of good manufacturing / fining practices for wines;
  2. criteria for methods of analysis available; and
  3. 3. background of scientific evidence.

Some food allergen-derived fining agents are used in winemaking, however, the use of a food allergen-derived fining agent would only pose a risk to allergic consumers if protein from the food allergen is left behind in the wine at the end of the winemaking process. It is understood that under normal conditions of use, fining agents are added at the lowest level required to achieve the purpose of clarifying the wine, and that a filtration process is normally used at the end to separate the fining agents from the clarified wine. Also, when these kinds of best practices are followed, no detectable protein from the food allergen should be left behind in the wine. However, where best practices are not followed, such as where larger amounts of fining agents are used, or less rigorous methods are used at the end to separate the fining agent from the wine, then protein from the food allergen could be present in the wine and labeling could be required. Winemakers will have to be aware of the winemaking process that they are using to fine their wines and whether or not this process can result in protein from a food allergen being present in a wine.

Events not to be missed in 2013

Registrations to two international conferences for the Australian grape and wine industry (to be held in Sydney, July 2013) will open next month. Register early to gain the benefit of discounted registration fees.

The 15th Australian Wine Industry Technical Conference is held every three years and is the premier technical conference and trade exhibition held for industry members. The program covers all aspects of the grape and wine business and provides a valuable opportunity for sharing of information and networking with industry colleagues. More than 1,000 national and international delegates are expected and will be held 13-18 July at the Sydney Convention Centre. See the website for further information (www.awitc.com.au).

WineHealth 2013 continues the series of scientific international conferences discussing the complex interaction of wine and health (which have been held previously in Italy, USA, Chile, South Africa and France over the past 17 years). In 2013, the next conference will be held in Sydney from 18-21 July at the Sydney Convention Centre and is open to anyone interested in this topic. Information on the program and speakers are on the website (www.winehealth.com.au).

ASVO Fellowship honours Peter Dry

Dr Peter Dry, AWRI’s Viticulture Consultant, was inducted as a Fellow of the Australian Society of Viticulture and Oenology at a gala dinner in Adelaide on 21 November. President of the Society, Dr Paul Petrie, said that Peter was selected for this honour because of his long-term contribution to the Society, particularly as editor of Viticulture Volumes 1 and 2 and as associate editor of the Australian Journal of Grape and Wine Research, and also for his service to the grape and wine industry through education, research and extension for more than 40 years. Peter becomes the sixth Fellow in the history of the Society and joins former AWRI staff members Dr Terry Lee and Dr Pat Williams.

Recent literature

John Fornachon Memorial Library at the AWRI delivers journal articles and loans books to Australian grapegrowers and winemakers. Books can be searched and requested via the Library catalogue – or you can email the AWRI with your request.

Recent AWRI staff publications

Borneman, A.R., Pretorius, I.S., Chambers, P.J. Comparative genomics: a revolutionary tool for wine yeast strain development. Current Opinion in Biotechnology http://dx.doi.org/10.1016/j.copbio.2012.08.006: 1-8; 2012.

Cozzolino, D., Cynkar, W., Shah, N. Varietal differentiation of grape juice based on the analysis of near- and mid-infrared spectral data. Food Analytical Methods 5 (3) : 381–387; 2012.

Dry, P. Garganega. Wine & Viticulture Journal 27 (5): p. 64; 2012.

Essling, M. Top 10 tips for effective spraying. Australian & New Zealand grapegrower & winemaker (584): p. 57; 2012.

Fudge, A.L., Schiettecatte, M., Ristic, R., Hayasaka, Y., Wilkinson, K.L. Amelioration of smoke taint in wine by treatment with commercial fining agents. Australian Journal of Grape and Wine Research 18 (3): 302-307; 2012.

Johnson, D. 2012 AWRI annual report. Australian & New Zealand grapegrower & winemaker (586): 84-87; 2012.

Krstic, M. Ask the AWRI: Timing of harvest is the key decision for winemakers. Australian & New Zealand grapegrower & winemaker (585): 38-39; 2012.

Hayasaka, Y., Parker, M., Baldock, G.A., Pardon, K., Black, C.A., Jeffery, D.W., Herderich, M. Assessing the impact of smoke exposure in grapes: development and validation of a HPLC-MS/MS method for the quantitative analysis of smoke-derived phenolic glycosides in grapes and wine. J. Agric. Food Chem. DOI: 10.1021/jf305025j: 1-33: 2012.

Scrimgeour, N., Wilkes, E. WineCloud provides future direction for winemakers. Australian & New Zealand grapegrower & winemaker (585): 65-69; 2012.

Roget, W. Benchmarking a continuous tartrate stabilisation system. Australian & New Zealand grapegrower & winemaker (585): p. 106; 2012.

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.