Greek scientists say that a Cretan white wine packaged in bag-in-box pouches loses its flavour and aroma far faster than in screw-top glass bottles.
Introducing their research pending in the June 2014 issue of Food Chemistry, Revi et al. note that organic acids (tartaric, malic, citric and acetic) and phenolics in wine have crucial effects on product quality.
Wine taste is determined by sweet (sugar), sour (organic acids) and bitter/astringent (polyphenols), they explain, while volatile compounds all contribute to wine aroma.
Vilana, the wine used for this study, is the main white variety on Crete, and the Peza appellation requires that it be made from 100% Vilana grapes: the wine’s fruity aroma includes lemon, orange, apple, pear notes.
Wine packaging is designed to protect against oxygen, CO2, moisture, light and aroma compounds – while its inertness, in terms of packaging compound migration, and sorption of volatile aroma compounds is also key.
Australian success in the bag
Pointing to the success of BIB packaging on the Australian market (more than half of wine consumed uses it), Revi et al. describe the conventional bag structure.
This is an outer plastic laminate layer including metalized polyester (PET) and an inner bag made of either low density polyethylene (LDPE) or ethylene vinyl acetate (EVA), packaged in paperboard.
But the scientists note that major drawback of such polyolefinic packaging materials is their capacity to adsorb volatile flavor compounds of wine (Brody 2007), while incomplete air tightness around polypropylene (PP) valve fitments also leads to flavor loss.
Testing commercially filled packages of the same Vilana wine (5 liter BIB and 1.5 liter screw cap bottles), Revi et al. examined classical quality measures, while an experienced wine-tasting panel also tried the wine from each under controlled conditions.
‘Deterioration in sensory quality’
Titratable acidity rose for BIB wine, total and free SO2 levels (it has an antimicrobial effect) fell 40% after 180 days of storage (versus 26% for the same wine in glass bottles); while a “substantial portion” of wine aroma contents were lost in BIB wine and color suffered.
“The deterioration in sensory quality of wine is most probably enhanced by the sorption of numerous volatile compounds by the polymeric packaging material,” Revi et al. write.
Of the two polymers tested, the LDPE lined pouch showed higher potential than EVA for sorption while glass proved the most inert packaging material for wine.
The wine tasting panel reported that wine retained acceptable quality for three months (90 days) when packed in either EVA and LDPE bags and six months (180 days) when packaged in glass.
The scientists say they are now working to extract and quantify the adsorbed volatile compounds from wine present in both LDPE and EVA polymeric films.
Title: ‘Effect of packaging material on enological parameters and volatile compounds of dry white wine’
Authors: Revi, M., Badeka, A., Kontakos, S., Kontominas, M.G.
Source: Food Chemistry 152 (2014) 331-339 http://dx.doi.org/10.1016/j.foodchem.2013.11.136