WINE grape producers may be prompted to re-think their drying methods after new research out of South Australia.
University of Adelaide researchers investigated the best methods of grape drying in order to produce better quality wine.
The research focused on three common techniques used to delay ripening in grapes:
- the use of antitranspirants;
- late pruning;
- late source limitation.
The researchers examined the results of 43 studies using statistical modelling techniques traditionally used in medical and psychological research.
Lead author and a PhD graduate Pietro Previtali said the antitranspirants were compounds applied to the leaves of plants to reduce transpiration.
"We found that applying antitranspirants when the grapes started to change colour caused larger ripening delays, and the ripening delay was larger when there were early and late season applications," Mr Previtali said.
"Late pruning is when pruning is postponed until after the apical buds have burst.
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"We found there was a larger delay in ripening when the vines were pruned later in the season, however the technique is less effective on high-yielding vines.
"Late source limitation, which removes a portion of the young leaf area that accumulates sugar during ripening, is likely to be more suitable in red grape varieties with higher sugar levels, while white grape varieties may be harvested too early for this treatment to be effective.
"We also observed larger ripening delays were achieved on high-yielding vines where sugar accumulates slower."
The work was done through the University of Adelaide's Department of Wine Science and Waite Research Institute and the Australian Research Council Training Centre for Innovative Wine Production.
Mr Previtali's PhD supervisor, associate professor Chris Ford said a number of factors can lead to higher sugar concentrations in grapes.
"Increased levels of carbon dioxide in the atmosphere, rising global temperatures and declining rainfalls, can lead to grapes ripening faster than normal," associate professor Ford said.
"This results in higher levels of alcohol, throwing off the balance of the wine and diminishing the quality of the product, while growers may need to postpone harvest altogether.
"This research can hopefully help growers make decisions that will generate higher yields and quality wine."
The research paper has been published in Horticulture Research, titled, "A systematic review and meta-analysis of vineyard techniques used to delay ripening."
In addition to associate professor Ford, co-authors on the publication were professor Kerry Wilkinson (University of Adelaide), Filippo Giorgini (University of Milano-Bicocca, Italy), Randall Mullen (E and J Gallo Winery, California, US) and Nick Dookozlian (E and J Gallo Winery, California, US).
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