14 Aug 2014

DNA Test For Wine

From Our Changing World, 9:46 pm on 14 August 2014

“Oh, it’s a beautiful thing," says Kirsten Creasy as she views a yeast colony under the microscope.

Wine-maker and oenologist Kirsten Creasy examines a yeast colony under a microscope. She is using DNA testing to work out what yeasts, bacteria and allergens are present in wine.

Wine-maker and oenologist Kirsten Creasy is using DNA testing to work out what yeasts, bacteria and allergens are present in wine Photo: RNZ / Katy Gosset

Both a wine maker and an oenologist at Hill Laboratories, she appreciates the business of wine production from both sides of the lens. And she believes lab work can go a long way towards helping New Zealand vineyards understand and improve their products. She says new tests can now track everything from allergens and bacteria to specific yeasts that may help produce low-calorie wine.

DNA in the Bottle

Kirsten Creasy says one of the most useful tools on offer is a rapid DNA test that has long been used in the medical industry but is relatively new for the wine sector.

‘We extract all the DNA from yeast and bacteria that’s growing in this wine and then we identify it and quantify it, so it’s a very exciting test that’s given a really, really great tool for wine makers.’

While traditional work has focused on what is in the wine itself, rapid DNA testing means the lab can also analyse bacteria fond in the vineyard or the wine barrels. Another relatively new test follows changes to European Union labelling regulations on allergens.

Kirsten Creasy says milk and egg are traditional fining agents used in wine making and the EU has given a particular regulatory limit for residues of these ingredients. Any export wines that do not meet these limits must be listed as possibly containing those products.

She says the lab has developed a test that uses an antigen/antibody reaction, coupled with a colour change, which can quantify how much of the allergenic egg or milk protein is left in the wine. 

Counting the Calories

Kirsten Creasy says she initially thought low-calorie wines might be “a bit trendy” but now believes they could be around for a while. This is an initiative by New Zealand Winegrowers, the national organisation representing the wine sector. The concept covers everything from the marketing of low-cal wines as better for health through to finding and breeding specific yeasts that are less effective at converting sugar into alcohol.

Future Challenges

Kirsten Creasy says, currently, there are only two regulatory tests required of the wine industry: one ensures the alcohol content stipulated on the bottle is within a variance of the actual wine, while the other requires sulphur levels to be kept within a prescribed limit.

But she says many New Zealand wines and, in particular, Sauvignon Blanc are bottled overseas and there’s concern within the industry about how to ensure that such products arrive in the condition they were sent in. She says, long-term, it may be that wine sent overseas is tested on arrival and measured against a digital fingerprint of the original wine back in New Zealand to provide traceability. And ultimately, she hopes that the suite of new lab tests available will be used, not just at the end of each vintage but throughout production, with the more detailed information informing each stage of the wine-making process.

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