Research puts something extra in your grapes

Researchers at the University of Adelaide have discovered a potential way to increase the amount of Vitamin C in grapes.

Senior lecturer Dr Christopher Ford and postgraduate student Seth de Bolt from the University of Adelaide's School of Agriculture, Food and Wine have made the significant breakthrough, in collaboration with their US colleagues at the University of California.

The researchers have identified an enzyme in grapes that helps convert Vitamin C, or ascorbic acid, into tartaric acid. Tartaric acid accumulates in grapes as they ripen and contributes greatly to taste, tartness and aging potential.

Dr Ford, a lecturer at the University's Waite Campus, says unlike other fruit acids, tartaric acid is synthesized from Vitamin C instead of sugars.

"We compared the acid content of 28 grape-related species and found one that produced no tartaric acid. This particular grape lacked one of the candidate enzymes that catalyses a key intermediate step of Vitamin C conversion," Dr Ford says.

"By manipulating this enzyme, we propose that grapes may be modified in such a way that their Vitamin C content can be significantly increased."

University of Adelaide Chair of Viticulture, Professor Steve Tyerman, says: "Besides the implications for Vitamin C content, there are also potential impacts on reducing a major cost in wine making.

"By understanding how the major acid in grape juice is synthesised, it will enable further discoveries on how to prevent the reduction in the level of the acid in warm climates.

"Currently this results in the need for tartaric acid to be added in the winemaking process at significant cost to the industry."

The findings were published in The Proceedings of the National Academy of Sciences late last month.

The study was supported by the Federal Government's Cooperative Research Centres Program.