In 1991 the sale of table wines in non-glass containers was allowed in Italy, including polylaminate, PET (polyethylene terephthalate), bag-in-box (BiB) and aluminium cans. Since 2008, Protected Designation of Origin wines can also be packaged in BiB (used mainly when buying bulk wine), if permitted by production regulations. Additionally, steel kegs have been authorized by EEC regulation 822-07 for the sale of wine on tap. In this case the container can withstand pressure of up to 100 atmospheres.

In Italy, many everyday wines packaged in paper products, aluminium and polyethylene are well accepted by consumers. In France you can also find mid-range and Appellation of Origin Controlled wines sold in cartons. These containers are eco-friendly, light and recyclable; the square-cornered shape makes all the handling phases of the product easy, right up to when it is consumed. Volumes range from 200ml to 1 liter for different types of consumers. Cartons allow wine to be preserved even longer than 12 months (the legal expiration date), and the packaging is a good barrier against light and oxygen damage because of the small amount of head space (Baroni et al., 2013).

Other rapidly spreading forms of packaging such as PET bottles and BiB allow a much shorter shelf life for wine—typically between two and nine months.

Plastic packaging materials may release unwanted substances into wine and can also modify aromatic properties through “flavor scalping” (the absorption of volatile aroma compounds), depending on the characteristics of the materials and molecules involved (Lunardelli et al., 2009). Other factors may influence this phenomenon, such as the volume of packaging in contact with the wine, wine pH, SO₂ level and storage temperature.

Another aspect to consider is the permeability of plastic materials, especially to oxygen, and consequent deterioration of the product. Wine producers should monitor the evolution of their products in contact with these materials in relation to expected storage times.

To reduce the environmental impact of packaging and transport, higher quality wines destined for aging can make use of lightweight glass bottles. The most suitable choice of packaging always depends on expected shelf life of the product and on the type of distribution and marketing planned.

Bag in box
BiB packaging refers to a bag hidden inside a cardboard box fitted with a tap for serving and a handle for transport. The BiB was invented by U.S. chemist W.R. Scholle in 1955 and became the “Wine Box” in 1965, thanks to the Australian winemaker T. Angove.

The bag is made of a multi-layered flexible film that must be physically resistant and a barrier against gases. It is made from polyester metalized with aluminium, plus a low-density polyethylene (LDPE) or ethylene-vinyl acetate (EVA) film in contact with the wine.

The external cardboard must be resistant to internal pressure, vertical compression, perforation and humidity; the tap must have a strong valve with low permeability to oxygen. Also, the convenient handle for transport has its own importance (Vimont 2014). The capacities used vary from 3 to 20 liters.

Use of BiB wine packaging, which accounts for 10% of the world wine market (Ducruet and Bach, 2014) and about 50% of Australian wine (Baroni et al., 2013), is spreading due to its numerous advantages. It is light and practical, and the wine contained in the bag can be consumed gradually as the residual product is protected from contact with the air. It allows wines to be preserved better for short periods (a maximum of two to three months), as observed by several authors.

Depending on the type of BiB used, humidity, temperature and preservation times, there are calculation models (Ducruet J., Bach B., 2014) that predict the quantity of oxygen that will reach the wine; this allows for more accurate levels of SO₂ to be added, remembering that it is necessary to minimize contact of wine and oxygen during the production stages before packaging. Under optimum conditions, the wines can be preserved for six months.

Studies, research and experimentation
Experiments carried out in Switzerland (Ducruet et al., 2011) with Chasselas and Pinot Grigio white wines in 3-liter BiBs showed that this packaging is interesting for selling early drinking wines (to be consumed within two to three months, at most). In fact, their high permeability to gases does not protect wine from oxidation and, when preserved for more than three months, losses of CO2 were observed; the color evolved toward intense yellow; oxidized notes were perceivable; the olfactory intensity and the floral and fruity notes were significantly less intense, as were the structure and length.

It has been observed that it is necessary to minimize contact between wine and oxygen during the production and packaging phases; moreover, the product should undergo sterile filtration and have high levels of free SO₂. Oxygen also reaches wine through the tap and the valve, as observed by Fu et al., (2009); furthermore, the film may absorb volatile compounds responsible for aroma. It is advisable for BiBs to be stored in an environment free of foreign odors, at a temperature of 12°-20° C with humidity between 20% and 50% to avoid damaging the cardboard.

Hopfer et al., (2012) conducted a comparison test between different types of containers used to package California Chardonnay preserved for three months at different temperatures (10°, 20° and 40° C); it studied glass bottles with natural cork closures, screwcaps, synthetic corks and two types of BiB—one packaged in a controlled atmosphere, the other under normal conditions—in the presence of oxygen. The temperature was the factor that most affected preservation, but an interaction between packaging and temperature was also observed; the wines packaged in BiB and preserved at 40° C showed a more intense color, less fruity aromas and more oxidized notes and volatility than the samples in glass bottles.

The volatile esters were lower, whereas some compounds typical of oxidized wines increased, such as 1,1,6-trimethyl-1,2-dihydronaphthalene, furfuryl ether. At 10° C, no significant differences were observed between the wines. The samples in BiB preserved at 20° C showed lower levels of ethanol and fruity aromas than those in glass. It was observed that the presence of oxygen at the moment of packaging in BiB did not produce any significant effects. At the end of the three months, the evolution of the wine in BiB was different from that in glass, both from a chemical and sensory point of view.

Also in studies by Revi et al. (2013), sensory assessment showed that the quality of the wines in BiB was acceptable if consumed within three months of packaging, compared to six months for glass bottles. In this case, the experiment was carried out on a dry white wine from Crete produced with Vilana grapes, preserved in dark glass bottles and in two types of 5-liter BiB—one in low-density polyethylene (LDPE) and the other in ethylene-vinyl acetate (EVA), preserved at 20° C for six months.

As in previous experiments, a significant and consistent decrease in volatile compounds of wine aromas was observed, both due to absorption by the plastic material (especially the LDPE) and to the imperfect seal of the valve. The BiB sample in LDPE also had an aroma of plastic after 30 days. The wines in BiB packaging were described as slightly oxidized after 90 days and “unacceptable” after 180 days of preservation.

E. Besseas (2014) carried out a study on 74 samples of wine from the Loire Valley packaged in BiB and collected from large retailers. The study showed that 80% of samples had been preserved for less than six months; within three months of packaging the level of free SO₂ halved and there were no discernible faults up to 102 days of preservation. Twenty-three percent of the samples had faults, and 50% of them were traceable to oxidation for wines packaged for more than 200 days, where free SO₂ had reduced by 75% compared to the starting value. The hedonistic assessment of wines in BiB was lower than that of similar wines in glass bottles.

PET
PET polyethylene terephthalate (a polyester commonly known as “plastic”) is a low-cost, light, transparent and resistant material that is widely used for food and drink packaging as well as early drinking wines. It has a low resistance to heat and light and can be permeable to gases. PET bottles can be single-layer or multi-layer. Multi-layer PET bottles have been developed to improve protection from oxygen, although they are more expensive and more difficult to recycle. They are made up of a PET structure with three or five layers of resin, which can be made using copolymers of ethylene vinyl alcohol or Nylon MXD6.

Studies, research and experimentation
Multi-layer PET bottles (OxSc-PET, i.e. barrier against oxygen) have been proven (Mentana et al., 2009) to have a performance similar to glass and superior to single-layer PET bottles. The influence of these materials on Apulian red and white table wines with a shelf life of about six months, preserved for seven months at 15°-18° C, has been studied and compared with glass bottles. The OxSc-PET bottles give more protection against oxidation and sensory properties than the single-layer ones, especially for red wines.

The same research group (Pati et al., 2010) compared the performance of PET bottles made from different materials and closed with screwcaps for a Merlot (35%)/Montepulciano (65%) wine produced in Apulia with carbonic maceration. It studied 0.3 mm-thick PLA 7000D bottles (i.e., polylactic acid), which are potentially more environmentally friendly than PET (single layer with a thickness of 0.3 mm) and glass. The samples were preserved for four months in the dark at 15°-18° C. The wine aged in PLA bottles experienced more rapid loss of quality than that in PET and glass bottles. It was calculated that the quantity of oxygen that penetrated the wine in the four months was nine times higher in PLA bottles than PET ones (98.4ml compared to 10.7ml). This resulted in a reduction in total SO₂, wine browning, increased absorbance at 420 nm and an increase in volatile acidity.

The differences on a sensory level were already clear after two months of preservation, but a panel judged the wine as being still pleasant and drinkable up to three months after bottling. In light of the results, the PLA bottles allow a wine to be preserved up to a maximum of three months, with the advantage of the packaging being that it’s biodegradable. In PET bottles, the phenomena of oxidation and “scalping” were observed, highlighted by absorbance at 420 nm and analysis of volatile compounds. However, there were no significant differences on a sensory level; for this reason, this type of bottle can be an alternative to glass if wines have an expected shelf life of four months of less from the packaging date.

Ghidossi et al., (2012) studied the quality evolution of some white and red Bordeaux wines (2008 vintage) packaged in different ways for a period of 18 months. They used bottles made of glass, single-layer PET (0.3 mm thick) and multi-layer PET MXD6 (0.4 mm thick), with capacities of 750ml and 185ml as well as 3-liter bag-in-boxes. For the white wine, the glass and multi-layer PET bottles proved to be the best barrier against oxygen; however, neither the single-layer, multi-layer PET bottles nor the BiBs allowed adequate preservation of the wine after 12 months. For red wine, differences were observed at the end of the test.

Dombre et al., (2015) studied the evolution of the aromatic profile of a rosé wine bottled in glass, virgin PET and recycled PET and preserved for five months. The wines differed, but only in some compounds. In the PET bottles there was a decrease in the compounds sensitive to oxygen, such as methionols, and the appearance of compounds typical of oxidized wine: ethyl pyruvate, furfural or dioxane compounds. Compared to tests in PET, those in recycled PET showed small differences. Loss of flavor was due to the chemical evolution of the wine rather than absorption by the PET. For the moderate permeability to oxygen, the use of virgin and recycled PET bottles may be adopted for wines with short shelf lives, but both can have a negative impact on quality if the wine is not consumed within a short period.

Maria Carla Cravero is a researcher with CREA, the Council for Research in Agriculture and Analysis of the Agricultural Economy, Research Centre for Enology in Asti, Italy

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