The Science Of Wine

This is where his career in wine science began. When he left secondary school in Upper Hutt, the university of choice was, naturally enough, the University of Victoria in Wellington. In the 1980s, he began studying a BA and BSc simultaneously. As if that wasn’t enough, he then entered the seminary at Mission Estate in Hawke’s Bay, travelling between there and the capital to complete both of his tertiary education goals. One provided him with a career; the other with a life choice and, inadvertently, the Mission also gave him hands-on experience in wine to back up the science he was learning at the time.

One of the first scientific papers on wine that he published was the “Measurement of the redox potential of wine”. It was in conjunction with J W Tomlinson at the Department of Chemistry at Victoria and was first published in August 1996.

But by the time he got to his second year of studying at Victoria, he was told that he had to choose between his BA and his BSc. Science won the day. Kilmartin found himself immersed in the electro chemistry of wine.

One of his science professors was interested in wine and had studied chemistry at Imperial College in London, which propelled Kilmartin’s interest in the subject. His studies at Mission Estate further supported that interest; professionally and personally.

When he wasn’t up to his ears in redox potential and chemistry at Victoria, he was attending theology lectures and helping out in the winery shop in Hawke’s Bay.

After graduating with a BSc from Victoria, he worked for 11 years in the Marist order in Wellington and Hawke’s Bay. His time in the seminary came to an end when he moved to Auckland in 1993 to do his PhD in analytical chemistry and food science. That was also the year that he met his partner, Jelena. Together they have a 14-year-old son.

He has since been developing a wine science programme to complement the viticultural research in Marlborough.

The most surprising thing he has discovered in wine science to date relates to the impact that temperature has on the storage of wine.
“It has a much greater impact than any other factor that we have studied so far when it comes to the preservation of fruity aromas in Sauvignon Blanc; the grape we have studied the most,” Kilmartin says.

“This grape’s esters hydrolise at a warmer temperature and much faster than I imagined; within a year of storing a wine at 20 degrees, you lose most of the fruity esters.”

This happens whether the wine is in tank or in bottle. At a lower temperature, fruity aromas can be preserved for significantly longer, Kilmartin says, and if the wine is stored at 5 degrees, its fruity aromas are preserved.

The research was part of his studies into antioxidants. This study programme saw Kilmartin and his students intentionally accelerate the wine’s aging process to see which antioxidants worked most effectively. 

The discovery was made about seven years ago and has begun to have a practical application for wineries today.

The other most significant discovery that he has made relates to the harvesting and oxidation of grapes when picked. Again, oxidation rates can – under certain circumstances – be far more rapid than he and his students originally anticipated.

“Oxidation during harvest is of absolutely critical importance,” he says.

“When grapes are being harvested there is a lot of enzymatic activity. If we don’t protect a juice adequately with SO2 after the harvest then the rate of oxidation can be frighteningly swift. The important thing is to get the antioxidants onto the grapes early in the field, so that you’ve always got some free SO2 present on their journey from the field to the winery.”

This enables winemakers to maximize thiols in the Sauvignon Blancs they produce, he says.

Some grapes are more prone to oxidation more swiftly; others less so.
“Some juices will chew through the oxygen more quickly and they need more ascorbic acid and sulfites added.”

Most of his research to date has been on Sauvignon Blanc, so this grape has formed the basis for his studies but Pinot Gris is now also under Kilmartin’s microscope. It is also showing significant levels of thiols.

“Some Pinot Gris has a passionfruit/grapefruit aroma as we have found in Sauvignon Blanc, but they are not as driven in that greener direction as Sauvignon Blanc.”

Most of the research work that he is involved in currently is being done at the University of Auckland’s East Tamaki campus, but the university now has the old Lion Breweries site in Newmarket, which is where the extract and polymer work
will eventually continue; when the new facilities have been finished. 

One of the new projects that Kilmartin is working on is a food based one, using antimicrobial agents to extend the shelf life of plastics that are used for fruit juices. 

“Naturally, this will have a wine application too and we are looking into using winery waste products for their antibacterial, antiviral and antifungal properties. Grape tannins that are in contact with plastic can give antibacterial and antioxidant properties to plastic itself; it’s a good use of winery waste materials.”