Machine picked grapes 'better for vintage'

LOCAL FORAY: A Marlborough vineyard has been snapped up by Rothschild, one of the world's most famous wine names.
LOCAL FORAY: A Marlborough vineyard has been snapped up by Rothschild, one of the world's most famous wine names.

Winemakers can stop grape picking and turn to machine harvesting, with new research finding it could produce better wine.

University of Auckland research is set to revolutionise winemaking, showing that machine harvesting produces higher levels of the aromas characteristic of New Zealand sauvignon blanc.

"Machine harvesting is well-established both here and overseas, but it has generally been considered second-best in terms of grape quality and purity," lead researcher Associate Professor Paul Kilmartin said.

"Our research provides the first published comparison of wines produced by machine and hand harvesting, and shows that machine harvesting results in higher levels of the passion fruit and grassy aromas that are so desirable in New Zealand sauvignon blanc."

Adding sulphur dioxide as soon as the grapes were harvested also resulted in higher levels of characteristic aromas, he said.

"Sulphur dioxide is widely used by winemakers to prevent oxidation and the growth of microbes, and is added at different stages of the winemaking process.

"We found that adding adequate sulphur dioxide prior to fermentation, to match grape juice oxidation status, stops naturally-occurring enzymes from chewing up the thiol compounds responsible for the passion fruit aroma, particularly during longer truck transport times."

He said it did not result in higher levels of sulphur dioxide in the final product however, as it was broken down by the yeast.

Kilmartin shared his findings with New Zealand winemakers earlier this year.

"Many have already started to re-examine their harvesting approaches in the light of this research," he said.

"One of the wineries we partner with has shifted to machine harvesting for their premium sauvignon blanc, to maximise the tropical fruit aromas in their wines."

Winemaker Murray Cook, from Villa Maria Estate, said the sulphur dioxide findings were also being used.

"Based on Paul's research we doubled the amount of sulphur dioxide added in the field for the 2012 Sauvignon blanc vintage, and the comments we're getting from blending are that the vintage is really strong."

Kilmartin presented the research at the American Society of Enology and Viticulture (ASEV) conference in the United States.

He would also present it at the International Workshop in Vineyard Mechanisation and Grape and Wine Quality in Italy next week.