(Academicwino) - As everyone who reads this blog probably knows, wine is traditionally stored in glass bottles with a cork seal. With the issue of climate change becoming much more dire with every passing day, new products that are more environmentally sound and sustainable are much more desired and needed.

In terms of wine packaging, there has been a lot of experimentation with different types of packaging, including bag-in-box wine and other plastic-based polyethylene terephthalate (PET) bottles. Glass bottles are heavier than bag-in-box or other plastic bottles, leading to an overall increase in the environmental footprint left by distributing and shipping these bottles all over the world. While plastics do certainly have their own issues when it comes to “environmental friendliness”, their cost of manufacturing and shipping is much lower than glass.

One problem with adopting new packaging solutions for wine relates to the ability of that new packaging to protect the wine against too much oxygen ingress, resulting in premature oxidation or other negative aromatic consequences. Another problem relates to the absorption by the packaging material of important aromatic compounds in the wine. In other words, the plastic might “suck out” some of the more desirable compounds, while allowing a lot of oxygen to pass through the material into the wine, all adding up to a potentially faulty or off-tasting wine.

A new study from the journal Food Chemistry aimed to address this issue of sensory changes in wine related to packaging materials. Specifically, the study examined the influence of packaging type on a rosé wine, comparing traditional glass bottles to plastic PET bottles and finally recycled plastic PET bottles.

Brief Methods

The wine used in this study was a rosé cinsault wine from the south of France given by UCCOAR – Val d’Orbieu. Enological parameters of the wine were: pH 3.3; ethanol 12.6%v/v; total acidity 3.4g/L; volatile acidity 0.17g/L; free SO236mg/L; and total SO2 130mg/L.

Wines were bottled in either glass, PET, or recycled PET, at 750mL per bottle.

All bottles were sealed with the NovatwistTM from Novembal (a polypropylene cap with a multilayer connective joint).

Bottles were stored under 400 lux light, and at 20oC for a total of 12 months.

Chemical analysis of the aromatic compounds in the wines occurred immediately after bottling, 3, 5, 9, and 12 months after bottling.

Results  (tip:  if you don’t care about the detailed results, just skip to the conclusion!)

36 different aromatic compounds were found in the rosé wine.

12 alcohols, 14 esters, 6 acids, 3 lactones, and 1 ketone.

*(unless otherwise noted, all concentrations listed below are for the 12 month time period)*

Esters

4 esters degraded up to 50% at 5 months, and between 70% and 90% at 12 months.

Isoamyl acetate degraded the most in the wines, losing 84% in glass bottles and 86% in both PET and recycled PET bottles.

Hexyl acetate, ethyl hexanoate, and ethyl octanoate degraded equally in wines stored in all bottle types.

Ethyl decanoate increased by 55% in wines stored in glass and PET bottles, but only increased by 30% in recycled PET bottles after 12 months.

This compound is responsible for “pleasant fruity notes” in wine.

The increase in wines stored in glass and PET bottles could result in increased fruity notes, though these characteristics would be less obvious in recycled PET bottles since ethyl decanoate did not increase by as much.

Decanoic acid degraded more in wines stored in recycled PET bottles than the other two bottle types.

Ethyl lactate increases were similar in wines stored in all bottle types.

Diethyl-malate (D-m) and ethyl hydroxyglutarate (EH) increased more in wines stored in glass bottles than PET bottles.

D-m increased by 250% in glass bottles and 180% in PET bottles

EH increased by 550% in glass bottles and 400% in PET bottles.

These increases look like a lot, but since these compounds have very high odor thresholds, these increases probably didn’t do too much to the aromatic profile of the wines.

Diethyl tartrate formed at a higher rate in wines stored in glass bottles than in PET bottles, with differences also seen between PET and recycled PET.

Isopropyl-3-methylbutanoate concentrations were greater after 12 months in wines stored in PET bottles compared with glass.

Ethyl butanoate was 2 times higher in wines stored in recycled PET bottles.

This difference could result in an improved fruity quality to the rosé wines in the recycled PET bottles compared to the other two bottle types.

Ethyl pyroglutamate concentrations were very low in wines stored in recycled PET bottles compared to the wines stored in the other two bottle types.

Ethyl pyruvate concentrations increased 2 times more in wines stored in both PET bottles compared with glass bottles.

Total ester concentrations after 12 months increased 76% in wines stored in glass bottles, 61% for wines stored in PET bottles, and 46% for wines stored in recycled PET bottles.