Exploring PET and BIB as possible alternative packaging for Sauvignon Blanc

by | Jan 1, 2020 | Oenology research, Winetech Technical

Polyethylene Terephthalate (PET) (left) and Bag in Box (BIB) packaging (right).

With consumers increasingly seeking more environmentally friendly packaging, it would be wise for producers to explore the innovative and creative packaging options available on the market.

Introduction to glass alternatives

Polyethylene Terephthalate (PET) is a plastic packaging widely used in the food and beverage industry. PET has several advantages: It is light, transparent, inexpensive, easily transformed into the desired shape and delivers sturdy packaging. The customisable shapes have transporting advantages potentially allowing 36% more space in a shipping container.1

PET is available in single-layer or multi-layer (three- or five-layer) packaging. Approximately 80% of barrier PET bottles on the market have multi-layer structure2 that should improve the protection of the contents from oxygen permeation.

Bag in Box® (BIB) consists of a resistant bladder (often plastic) housed in a sturdy cardboard box fitted with a tap for serving and a handle for transport. The bladder usually comprises of several layers of flexible film in the same way as PET multi-layer bottles.

One of the biggest advantages of using BIB for Sauvignon blanc is the fact the wine contained in the bag can be consumed gradually as the residual product is protected from contact with air. This allows better preservation of the wine over short periods.

Experimental layout

A Sauvignon blanc wine was bottled under specialist supervision using a semi-automatic twin head liquid filling machine inerted with CO2 gas (Table 1). For the filling of the BIB, a rod was used to transfer the wine rather than using an automatic process. All bottles were sealed with screwcaps and bottles were stored upright at 20ºC in the dark for 18 months. Analyses of the wines were done at various intervals: Immediately after bottling and then after three, six, nine, 12 and 18 months.

Results

Oxygen permeability

Oxygen can permeate through the container and dissolve in the wine, however, it is important to remember that while this permeation occurs, dissolved oxygen is consumed by wine components initiating oxidation reactions. The rate at which the oxygen permeates and dissolves in the wine, and the rate at which the dissolved oxygen is consumed by wine components, will ultimately determine the amount of oxygen present in the dissolved form. Therefore, if the rate of permeation is higher than the rate of consumption, the dissolved oxygen in the wine will increase over time.

The initial oxygen measurement of the wine was 0.73 mg/L. After three months’ storage, the oxygen concentration was as follows:

  • Glass(750), Glass(185) and PETmulti(750): The oxygen content decreased post-bottling and remained low (below 0.1 mg/L) during the entire storage period.
  • PETmulti(185) and BIB: The oxygen concentration was around 0.5 mg/L. The concentration remained low during the storage period, however, at 18 months, the dissolved oxygen content of the wine in the BIB spiked to around 1.8 mg/L.
  • PETmono(750) and PETmono(185): Oxygen concentrations increased to around 1 mg/L and 2.3 mg/L respectively after three months’ storage. Concentrations then remained stable with a further increase in oxygen observed for PETmono(185) after 18 months.

Therefore, the containers that fared the best during the entire 18 months storage were the glass and PET multi-layer packaging. BIB also performed relatively well during the initial 12 months, after which an increase in oxygen was observed. The PET mono-layered packaging showed unacceptable oxygen uptake already during the initial stages of storage. The volume of the container also played an important role with the smaller volume containers taking up more oxygen. The wine volume to packaging surface ratio can play an important role in this observation and should be considered.

Sulphur dioxide

The decrease of sulphur dioxide is a useful marker for investigating the amount of oxygen consumed in wine (in a comparative way). An initial concentration of 30 mg/L free SO2 was measured in the wine prior to packaging. As is often seen in the industry, a decrease in free SO2 was observed three months after packaging. All treatments had an SO2 concentration of around 25 mg/L with the exception of PETmulti(185) and PETmono(185) for which the concentration measured around 21 mg/L.

From there on, the SO2 content in the various treatments started to differ significantly. After six months, Glass(750) and BIB still had about 20 mg/L of free SO2 after which the SO2 content in the BIB decreased to below 10 mg/L (already at nine months). The SO2 in the Glass(750) remained stable for the remainder of the 18 month storage period. The concentration of SO2 in the Glass(185) and PETmulti(750) hovered above 10 mg/L SO2 from six months onwards, while PETmulti(185) and both PETmono were well below 10 mg/L.

Carbon dioxide loss

In general, over the entire storage period, a decrease in dissolved CO2 was observed. This can have a significant sensory implication especially for Sauvignon blanc wine resulting in a wine that is perceived as less fresh or even flat. The treatments all differed in their rate of CO2 decline, however, it was evident that the glass bottles preserved the CO2 best.

Aroma compounds

The volatile thiols (aroma compounds responsible for the tropical fruit aroma in wine), declined during the storage period (3MH initial concentration 600 ng/L). After six months, Glass(750) had the highest concentration of 3MH at 500 ng/L. Surprisingly, PETmono fared relatively well and still had 3MH concentration of between 400 and 500 ng/L. The rest were all below 400 ng/L. After 18 months, all treatments were below 200 ng/L with Glass(750) and Glass(185) showing marginally higher values compared to the rest.

Initially, no oxidation-related compounds were detected in the wine, however, after 12 and 18 months’ storage, an increase in the oxidation compounds phenylacetaldehyde (honey and floral-like aroma), methional (potato-skin aroma) and sotolon (curry nuances), was observed. For all the compounds measured, a significant increase was seen for both PETmono packaged wines. For the other packaging options, variable results were obtained.

Sensory analysis

Judges were asked to score wines according to their “Sauvignon character” and “oxidative evolution” after six, 12 and 18 months. The wines bottled in glass, scored the highest for “Sauvignon character” during all the evaluations. Of the alternative packaging, PETmulti(750) showed the most promising result. The judges also reported an increase in “oxidative evolution” over time with the highest scores given to PET and BIB containers, again with PETmulti(750) showing most promising results out of all the alternative packaging options tested.

Conclusions

From the results reported in these studies, the future of alternative packaging for storage of wine is looking bleak. However, ongoing technological advancements could lead to packaging with less oxygen permeability. Other packaging options, such as aluminium cans, cartons and steel kegs (for wine on tap), also show potential and deserve further investigations.

It is evident that for wines that will be consumed relatively quickly after bottling (which is often the case for Sauvignon blanc), alternative packaging is still a viable option, especially if the wines are stored at a low temperature. The most suitable choice of packaging depends on the expected shelf life of the product and on the type of distribution and marketing planned.

Abstract

Of course, when considering alternatives to glass, various factors need to be taken into account, such as processing constraints, the cost of the material and the target consumer acceptance and expectations.3 The challenge is to find an alternative which is more environmentally friendly and less expensive, all the while maintaining the chemical and sensory composition and quality of the wine.

Assuming the packaging itself does not alter the wine by removing wine aroma (absorption) or adding unnatural compounds, oxygen permeability would be the main factor that would cause a decline in wine quality. This is especially important for Sauvignon blanc as the varietal aroma are often dependant on oxidation sensitive aroma compounds, such as the volatile thiols. A study titled “The influence of packaging on wine conservation”,4 investigated the evolution of a Sauvignon blanc wine packaged in the different containers over an 18 month period. The evaluation was done by measuring the dissolved gasses, certain wine constituents, as well as analysing the sensorial properties of the wine.

References

  1. Gerber, B. PET wine bottles: Plastic is fantastic. http://www.conca.co.za/index.php?option=com_content&view=article&id=159:pet-wine-bottles-plastic-is-fantastic&catid=37:winemaker&Itemid=63.
  2. Van Bree, I., De Meulenaer, B., Samapundo, S., Vermeulen, A., Ragaert, P., Maes, K.C., De Baets, B. & Devlieghere, F., 2010. Predicting the headspace oxygen level due to oxygen permeation across multilayer polymer packaging materials: A practical software simulation tool. Innovative Food Science and Emerging Technologies 11(3), 511 – 519. https://doi.org/10.1016/j.ifset.2010.01.007.
  3. Winder, B., Ridgway, K., Nelson, A. & Baldwin, J., 2002. Food and drink packaging: Who is complaining and who should be complaining. Applied Ergonomics 33(5), 433 – 438. https://doi.org/10.1016/S0003-6870(02)00026-1.
  4. Ghidossi, R., Poupot, C., Thibon, C., Pons, A., Darriet, L., Riquier, G., De Revel, G. & Mietton Peuchot, M., 2012. The influence of packaging on wine conservation. Food Control 23, 302 – 311.
  5. Besseas, E., 2014. Zoom sur la qualité des vins du val de Loire commercialisés en BIB®, pp. 7 – 10.
  6. Hopfer, H., Ebeler, S.E. & Heymann, H., 2012. The combined effects of storage temperature and packaging type on the sensory and chemical properties of Chardonnay. Journal of Agricultural and Food Chemistry 60(43), 10743 – 10754. https://doi.org/10.1021/jf302910f.
  7. Revi, M., Badeka, A., Kontakos, S. & Kontominas, M.G., 2014. Effect of packaging material on enological parameters and volatile compounds of dry white wine. Food Chemistry 152, 331 – 339. https://doi.org/10.1016/j.foodchem.2013.11.136.

– For more information, contact Dr Carien Coetzee at carien@basicwine.co.za.

 

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