The Institute of Vine and Wine Sciences of Bordeaux has just published a presentation, based upon 2 years of careful scientific research, which concludes that the quality of white wine tends to degrade significantly and noticeably within just six months of being packaged in PET (plastic) or bag-in-a-box packages instead of glass. These results are very interesting for a number of reasons.

I think many people assume degradation of wine would be more noticeable with red than white. The opposite appears to be true. The most significant effect of the alternate packaging on red wines within 6 - 12 months was loss of SO2. This can lead to spoilage in the wine. However, increases in oxygen and decreases in carbon dioxide within the enclosures is limited in the red wines though because the oxygen is consumed by the red wine's phenolics. Studies on red wine are continuing to see the effects of prolonged storage in the various enclosures.

White wines have much less phenolic content than reds though, due to lesser skin contact during fermenation. Therefore, the white wines can't counteract the relative oxygen porousity of the PET and bag-in-a-box. The result is that white wines not only lose significant amount of SO2 (a preservative) over time in these packages, they also lose a lot of CO2 and gain considerable O2. The degradation of the wine can be both seen, because the white wines get darker as they oxidize, and smelled/tasted. The Sauvignon Blanc took on "rotten fruit" flavors.

These differences were perceived by both expert and novice tasters. While certain variations in wine quality may not be obvious to the casual wine drinker, the changes seen in this study were great enough to be noticed. Of course, the longer the wine was stored in PET or bag-in-a-box, the greater the degradation and the easier it was to perceive. Within 12 momths, the white wines were considered "fully oxidized."

While few would have thought PET or bag-in-a-box to be suitable for holding wine more than a year, I suspect a lot of consumers and people in the trade would have thought white wines would hold up much better within a 6-month timeframe. I believe such changes within 6 months are problematic. While consumers may be unlikely to leave such packages of wine sitting around at home for lengthy periods, wine takes time to reach retail shelves after packaging. Once at retail, it may also sit for months on the shelves. At a minimum, it seems that very conservative "best consumed by" dates should be printed on each package. [While the affects on the wine are signficant at 6 months and drastic at 9 or 12, they are even noticeable after just 4 months.]

Size does matter. Two sizes for each type of bottle were tested: standard 750ml  and 187ml "single-serve" bottles. The small glass bottles did not preserve the wine nearly as well as the standard size. That said, for the most part, the small glass bottles still outperform the other packages and the differences between the small and large glass bottles of white wine after one year were more obvious by sight than taste. As you might expect, performance of the 187ml PET bottles was awful.

Hereafter, I shall neither give wine to my pets or PET my wine.

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This article is original to NorCalWine.com. Copyright 2010 NorCal Wine. The ISVV logo is the property of that institution. All rights reserved.

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