Scientists urge bag-in-box wine fans to 'keep it cool'

By Ben Bouckley

- Last updated on GMT

Bag-in-box wines are more likely than bottled peers to develop unpleasant flavors, aromas and colors when stored at warm temperatures, according to a new study looking at US Chardonnay.

Published in the American Chemical Society’s Journal of Agricultural and Food Chemistry​, the study by Hopfer et al. – using wines supplied by Constellation Brands – emphasizes the importance of consumers storing bag-in-box wine at cool temperatures.

The study also holds significance for the wine supply chain, with some industry sources claiming there is move away from selling bottles to boxes in the on-premise trade, for instance, specifically in the UK.

Helen Hopfer and her colleagues at the Department of Viticulture & Enology at University of California, Davis, explained that wine-based compounds react with oxygen in the air to change the way wine looks, tastes and smells, and that these reactions speed up with increasing temperatures.

Wine times are a-changin'

Adding that many wine brands are moving away from traditional wine packaging, glass bottles sealed with a natural cork, and trying synthetic corks, screw caps or wine in plastic bags inside cardboard – the team said it wanted to work out how such transitions affected the taste and aroma of wine under different conditions.

The authors studied how different storage temperatures affected California Chardonnay stored for three months in different packages: natural and synthetic corks, screw caps and two different bag-in-box containers.

Using chemical analysis and a panel of trained testers, Hopfer et al. found that storage temperature had the biggest impact on all of the wines (all of which were unoaked) and that there were no significant sensory differences between wines stored at 10C.

“[But] the packaging type also influenced the properties of the wines. Especially, the BIB samples showed severe and accelerating aging as compared to the three bottle treatments, which was significant for the two higher storage temperatures of 68F (20C) and (104F) 40C,”​ the team wrote.

Darker with vinegar notes

Bag-in-box wine stored at 68F and 104F aged significantly faster than bottled wines, becoming darker and developing vinegar notes. All wines tested aged better when stored at 50F.

“The largest changes were observed with the highest storage temperatures 104F, independent of the packaging,”​ Hopfer et al. wrote.

They added that all samples showed signs of oxidation at 104F, and were described by the sensory panel as oxidizes, musty and sulfur, were lower in lightness and green color and higher in yellow color.

Similarly, chemical analyses for color changes, volatile profiles and basic chemical parameters showed that 40C samples were darker, less green and more yellow.

At this temperature, all samples had lower amounts of free and total SO2, ethanol and lower TA. Oxidation and aging compounds increased in concentration: including diethyl succinate, TDN, straight and branched alcohols.

Meanwhile, fruit-related compounds such as acetates and terpenoids decreased with increasing storage temperatures.

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