"Until now most research has focused on the dangers of oxidation, such as whether or not it is beneficial to use screwcaps or add antioxidants to the wine. We have shown that in fact, temperature is the most important consideration in retaining fruity characteristics during storage.
"Our results show that wines in cold storage retain these desirable characteristics for much longer, and this has important implications for how producers, exporters, retailers, and consumers handle their wines. Well-managed refrigeration could help to improve the consistency of quality wines sold here and overseas, and allow the wine industry to cope with changes in supply and demand from year to year."
Researchers from The University of Auckland's wine science programme had earlier shown that two aromatic compounds, called thiols, which impart passion-fruit, grapefruit, and herbaceous aromas, are present at particularly high levels in New Zealand Sauvignon Blanc.
The first phase of the current research showed that in commercial wines stored at room temperature, levels of the least stable thiol, called 3MHA, declined by around 40 per cent in the three months after the wine was bottled and were almost undetectable after two years. These changes seemed to be unrelated to exposure to oxygen. Levels of the second thiol, 3MH, increased briefly and then declined only slowly, while a number of fruity esters also declined rapidly in the bottle.
The second phase of the research, studying commercial wines stored at a range of temperatures for 18 months, showed that the rate of loss of 3MHA and other fruity esters was three times lower at 5°C compared with 18°C, confirming that the change in aroma profile over time was highly dependent on temperature. Wines more than 2-3 years old were also found to have minimal 3MHA levels, and tended to be lower in tropical fruit characteristics and to have more prominent capsicum and canned asparagus aromas.
The research was conducted as part of the Sauvignon Blanc programme funded by the New Zealand Foundation for Research Science and Technology. The latest results have been reported in New Zealand Winegrower and more detailed reports will be published and presented at industry conferences in coming months.
The researchers will now begin developing models to predict changes in aroma profile over time and at different storage temperatures, to help winemakers manage the quality of their finished product.
In the meantime, they suggest that consumers who purchase several bottles of their favourite Sauvignon Blanc toward the end of the year consider storing it in the refrigerator to ensure that it is still at its best in several months' time.
