Glass bottles still dominate the market as the most popular wine packaging. The use of alternative vessels is known to date back to 1917, during World War I, when the French army supplied its soldiers with wine rations in metal cans. In the mid-1930s, when technology made it possible to package food and drink on a large scale, the first canned wines arrived on the market. In 1936, the first wine in a can, a Muscatel, was offered by Acampo, a California-based winery, which was followed by a similar product from Vin-Tin-Age.
Since 1936, several wineries have tried to can their wines, including Carina Kano-wine California White Port in 1954 and attempts by both Villa Bianchi Winery and Taylor California Cellars in 1979. However, since the beginning, canned wines encountered some related problems—including early appearance of turbidity in wine (maximum haze occurs at pH 3.8), degradation of the plastic liners, and corrosion of the cans themselves—which gave the wine an unpleasant, reductive, sulfur (S) smell due to the reduction of sulfur dioxide (SO2) to hydrogen sulfide (H2S). Although the issue with aluminum (Al) clouding, which is considered to form at Al concentrations >10 mg/L, has been resolved, the issue of the S-related off-flavor persists.
The worldwide market for canned wine was valued at ~$211.4 million in 2020, and it is likely to rise at a compound annual growth rate of 13.2% until 2028. In the United States, a survey across 25 states found more than 250 winemakers and 600 wine-in-a-can products, including Sauvignon blanc, Chardonnay, Muscat, and Pinot noir.
Despite the fast-growing nature of the product category and the great market forecast, concerns about the quality of canned wines remain. Unfortunately, these concerns lead to a consumer perception of canned wines as low-quality and with limited shelf-life, which must be addressed by the wine industry.
In view of the complex and multifactorial nature of the problem, it is reasonable to assume an integrated approach is needed to identify strategies to increase the shelf life of canned wines. In canned wines, the rotten-egg aroma of H2S is favored over the cooked-vegetable aroma of MeSH due to the low redox potential that shifts the balance of S compounds toward H2S. Further risk factors include the pH, as well as the levels of SO2, metals (particularly Al), O2, and Cl in the wine. In particular, the impact of Al on H2S content seems to be mitigated at a high total O2 level and high pH (>3.5) together with low levels of molecular SO2 and Cu (<0.2 mg/L).
Increasing dissolved O2 in wines raises their redox potential and shifts the balance of S compounds toward the less odorous forms. However, the corrosion of Al gradually increases in aqueous solutions as the dissolved O2 content increases from 0 to 4.0 mg/L. The control of O2 transfer was recently addressed by the closure industry, which developed screwcaps allowing control of the O2 transfer rate, permitting metered O2 ingress as required. For example, the Korked spin technology uses a membrane with controlled permeability interposed between the Al capsule and the inside of the bottle, which allows the microoxygen exchange. A similar approach was patented for metal cans as well. Obviously, even the best product packaging should be tested for each situation, taking into consideration the side effects of the redox reaction of flavonoids and ethanol on overall wine quality.
The adjustment of wine pH is a very basic practice, with the main purposes of achieving product stability and satisfying the consumer. Similarly, practical approaches to reducing SO2 are common knowledge in winemaking. Thus, winemakers can modify both pH and SO2 in canned wines as needed.
Finally, another effort involves the reduction of metal content in wine before and after packaging. Levels of electrochemically labile (free) Cu >25 μg/L limit the formation of free H2S. However, labile Cu is only a small fraction of total Cu; in commercial wines, the nonlabile form is mainly bound to organic acids and S-containing compounds. More recent insights have shown that the average first-order decay rate at which labile Cu is bound in wines is 0.0075 ± 0.002 after bottling. Among the several approaches to reducing metals in wine, the use of the copolymer PVI/PVP seems the most suitable. PVI/PVP is a polyvinyl imidazole and polyvinyl pyrrolidone adsorbent cross-linked copolymer commonly used in winemaking as a fining agent to scavenge several metals from wine. The addition of 20 to 50 g of copolymer per 100 L of wine will generally remove most of the Cu and H2S complexes in white wines, minimizing the risk of the latent development of reductive aroma due to H2S release from metal complexes. Together with metal-removing fining agents, the use of a suitable filtration system can further decrease the risk of latent H2S release from Cu-H2S complexes. Diatomaceous earth with depth filtration has been shown to be a more effective filtration system than a polyethersulfone membrane for the removal of 50 to 97% of sulfide-bound forms of Cu (Cu fraction III). However, further work is required to scale up these preliminary findings and develop practices based on an individual wine’s composition and style. Regarding Al, the next generation of cans should use improved cross-linked polymers to reduce Al migration during wine storage. Thus, there is a need to conduct new studies with a transdisciplinary approach to understand the specific interactions between product and container, the technological peculiarities of the canning process, and the physicochemical and sensory complexities of canned wine during storage.
Reference article
Versari A, Ricci A, Moreno CP and Parpinello GP. 2023. Packaging of wine in aluminum cans – A review. Am J Enol Vitic 74:0740022. DOI: 10.5344/ajev.2023.22071
