During the 2019/2020 bushfire season in Australia, extensive testing of grape and wine samples for smoke taint markers was conducted by both Winechek Laboratories and AWRI Commercial Services.
A number of observers commented that the results from the two laboratories appeared to be inconsistent and a greater understanding of how they related was needed. A study, commissioned by Wine Victoria, was undertaken to compare the results of these tests from the two labs. The report on this study is now available below.
Basically, the report found that the two methods provide different, but valid, results.
The reason for the different results was found to be due to the two laboratories using slightly different methods to determine the levels of free and bound smoke markers in grapes and wine. It should be noted that there is no international standard for the measurement of smoke markers and such a standard is unlikely to be adopted in the near future.
The differences between the test methods are driven not by simple choice but by various factors including the available equipment and resources at each organisation, as well as the underlying background datasets each organisation has developed historically.
For grape analysis the direct comparison of results from the two laboratories is possible for the volatile analytes guaiacol, m-cresol and p-cresol (and perhaps o-cresol with some care). For bound analytes there is a strong correlation between results for the pairs methylsyringol gentiobioside/4-methylsyringol and syringol gentiobioside/syringol, although care must be taken in comparing absolute values as the correlations are not a simple one to one relationship. Comparison to an internal dataset, generated using the same method, is therefore valid.
The full report below has more detail on the findings, and the statistical report has a detailed analysis on the differences between the methods.
Learn more about the importance of a smoke taint test by downloading the Winechek Smoke Taint Fact Sheet.
Smoke from fires, particularly bushfires, can affect the flavour of grapes and the wine made from them. The impact of smoke on grapes and the resultant wine varies considerably and a lot of research is being done at the moment to better understand this important issue.
Wine made from grapes that have been smoke affected have been described as having some of the following attributes: “burnt” “ashtray” “charred” “salami” “disinfectant” etc. Wine can be unfit for sale if the smoke taint is too great. You can find out the impact smoke has had on your grapes/wine by conducting a smoke taint test.
When are grapes most susceptible to smoke taint?
The time of the season is critical for the impact that smoke uptake can cause. Grapes have a low to medium uptake potential in the early stages of the season. However, from around 7 days post veraison until harvest the uptake of smoke into grapes is at its highest. The exact levels and duration of exposure to smoke that will cause taint has still not been precisely determined.
What is involved in a smoke taint test & how is smoke taint measured?
The key compounds that influence taint in grapes and wine have been shown to be the following volatile phenols:
One major issue is that these compounds can be found in juice and wine in the form of glycosidic conjugates—that is as bound compounds. If only the free portion is measured then this may be an underestimation of the potential problem.
Here at Winechek, we recommend you consider conducting a smoke taint test. This is done by analysing both the free and bound component of these compounds to fully assess the samples.
6S005 Smoke Taint (Free & Bound) in Grapes $225+GST
6S006 Smoke Taint (Free & Bound) in Juice & Wine $195+GST
When should grapes be analysed?
The most suitable time to analyse and conduct a smoke taint test on your grape samples is closest to harvest as possible when the berries have sufficient ripeness to enable fermentation.
It is also recommended that winemakers conduct small scale ferments to conduct a sensory assessment.
What sample is required?
Smoke Taint Sampling Instructions
500 g representative sample of berries or a sulfured 100 mL juice sample are required to conduct an accurate smoke taint test.
Smoke Taint Analysis
The Winechek smoke taint analysis report provides 14 analytical results. Each analyte can be detected down to a level of 1ppb (part per billion)
Learn more about the importance of conducting a smoke taint test today—download the Winechek Smoke Taint Fact Sheet.
EASYTEST SAMPLE SYSTEM FOR SMOKE TAINT TESTING - DOC
EASYTEST SAMPLE SYSTEM FOR SMOKE TAINT TESTING - PDF
© Winechek Laboratories 2019. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without the prior written permission of the publisher.
